[RFC PATCH 05/28] drm/gpusvm: Add support for GPU Shared Virtual Memory
Matthew Brost
matthew.brost at intel.com
Wed Oct 16 03:18:30 UTC 2024
On Wed, Oct 09, 2024 at 12:50:42PM +0200, Thomas Hellström wrote:
> Hi, Matthew.
>
> Some comments below around migrating to SRAM.
>
>
> On Tue, 2024-08-27 at 19:48 -0700, Matthew Brost wrote:
> > This patch introduces support for GPU Shared Virtual Memory (SVM) in
> > the
> > Direct Rendering Manager (DRM) subsystem. SVM allows for seamless
> > sharing of memory between the CPU and GPU, enhancing performance and
> > flexibility in GPU computing tasks.
> >
> > The patch adds the necessary infrastructure for SVM, including data
> > structures and functions for managing SVM ranges and notifiers. It
> > also
> > provides mechanisms for allocating, deallocating, and migrating
> > memory
> > regions between system RAM and GPU VRAM.
> >
> > This mid-layer is largely inspired by GPUVM.
> >
> > Cc: Dave Airlie <airlied at redhat.com>
> > Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> > Cc: Christian König <christian.koenig at amd.com>
> > Cc: <dri-devel at lists.freedesktop.org>
> > Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> > ---
> > drivers/gpu/drm/xe/Makefile | 3 +-
> > drivers/gpu/drm/xe/drm_gpusvm.c | 2174
> > +++++++++++++++++++++++++++++++
> > drivers/gpu/drm/xe/drm_gpusvm.h | 415 ++++++
> > 3 files changed, 2591 insertions(+), 1 deletion(-)
> > create mode 100644 drivers/gpu/drm/xe/drm_gpusvm.c
> > create mode 100644 drivers/gpu/drm/xe/drm_gpusvm.h
> >
> > diff --git a/drivers/gpu/drm/xe/Makefile
> > b/drivers/gpu/drm/xe/Makefile
> > index b9670ae09a9e..b8fc2ee58f1a 100644
> > --- a/drivers/gpu/drm/xe/Makefile
> > +++ b/drivers/gpu/drm/xe/Makefile
> > @@ -25,7 +25,8 @@ $(obj)/generated/%_wa_oob.c
> > $(obj)/generated/%_wa_oob.h: $(obj)/xe_gen_wa_oob \
> >
> > # core driver code
> >
> > -xe-y += xe_bb.o \
> > +xe-y += drm_gpusvm.o \
> > + xe_bb.o \
> > xe_bo.o \
> > xe_bo_evict.o \
> > xe_devcoredump.o \
> > diff --git a/drivers/gpu/drm/xe/drm_gpusvm.c
> > b/drivers/gpu/drm/xe/drm_gpusvm.c
> > new file mode 100644
> > index 000000000000..fc1e44e6ae72
> > --- /dev/null
> > +++ b/drivers/gpu/drm/xe/drm_gpusvm.c
> > @@ -0,0 +1,2174 @@
> > +// SPDX-License-Identifier: MIT
> > +/*
> > + * Copyright © 2024 Intel Corporation
> > + *
> > + * Authors:
> > + * Matthew Brost <matthew.brost at intel.com>
> > + */
> > +
> > +#include <linux/dma-mapping.h>
> > +#include <linux/interval_tree_generic.h>
> > +#include <linux/hmm.h>
> > +#include <linux/memremap.h>
> > +#include <linux/migrate.h>
> > +#include <linux/mm_types.h>
> > +#include <linux/pagemap.h>
> > +#include <linux/slab.h>
> > +
> > +#include <drm/drm_device.h>
> > +#include "drm_gpusvm.h"
> > +
> > +/**
> > + * DOC: Overview
> > + *
> > + * GPU Shared Virtual Memory (GPU SVM) layer for the Direct
> > Rendering Manager (DRM)
> > + *
> > + * The GPU SVM layer is a component of the DRM framework designed to
> > manage shared
> > + * virtual memory between the CPU and GPU. It enables efficient data
> > exchange and
> > + * processing for GPU-accelerated applications by allowing memory
> > sharing and
> > + * synchronization between the CPU's and GPU's virtual address
> > spaces.
> > + *
> > + * Key GPU SVM Components:
> > + * - Notifiers: Notifiers: Used for tracking memory intervals and
> > notifying the
> > + * GPU of changes, notifiers are sized based on a GPU
> > SVM
> > + * initialization parameter, with a recommendation of
> > 512M or
> > + * larger. They maintain a Red-BlacK tree and a list of
> > ranges that
> > + * fall within the notifier interval. Notifiers are
> > tracked within
> > + * a GPU SVM Red-BlacK tree and list and are
> > dynamically inserted
> > + * or removed as ranges within the interval are created
> > or
> > + * destroyed.
> > + * - Ranges: Represent memory ranges mapped in a DRM device and
> > managed
> > + * by GPU SVM. They are sized based on an array of chunk
> > sizes, which
> > + * is a GPU SVM initialization parameter, and the CPU
> > address space.
> > + * Upon GPU fault, the largest aligned chunk that fits
> > within the
> > + * faulting CPU address space is chosen for the range
> > size. Ranges are
> > + * expected to be dynamically allocated on GPU fault and
> > removed on an
> > + * MMU notifier UNMAP event. As mentioned above, ranges
> > are tracked in
> > + * a notifier's Red-Black tree.
> > + * - Operations: Define the interface for driver-specific SVM
> > operations such as
> > + * allocation, page collection, migration,
> > invalidations, and VRAM
> > + * release.
> > + *
> > + * This layer provides interfaces for allocating, mapping,
> > migrating, and
> > + * releasing memory ranges between the CPU and GPU. It handles all
> > core memory
> > + * management interactions (DMA mapping, HMM, and migration) and
> > provides
> > + * driver-specific virtual functions (vfuncs). This infrastructure
> > is sufficient
> > + * to build the expected driver components for an SVM implementation
> > as detailed
> > + * below.
> > + *
> > + * Expected Driver Components:
> > + * - GPU page fault handler: Used to create ranges and notifiers
> > based on the
> > + * fault address, optionally migrate the
> > range to
> > + * VRAM, and create GPU bindings.
> > + * - Garbage collector: Used to destroy GPU bindings for ranges.
> > Ranges are
> > + * expected to be added to the garbage
> > collector upon
> > + * MMU_NOTIFY_UNMAP event.
> > + */
> > +
> > +/**
> > + * DOC: Locking
> > + *
> > + * GPU SVM handles locking for core MM interactions, i.e., it
> > locks/unlocks the
> > + * mmap lock as needed. Alternatively, if the driver prefers to
> > handle the mmap
> > + * lock itself, a 'locked' argument is provided to the functions
> > that require
> > + * the mmap lock. This option may be useful for drivers that need to
> > call into
> > + * GPU SVM while also holding a dma-resv lock, thus preventing
> > locking
> > + * inversions between the mmap and dma-resv locks.
> > + *
> > + * GPU SVM introduces a global notifier lock, which safeguards the
> > notifier's
> > + * range RB tree and list, as well as the range's DMA mappings and
> > sequence
> > + * number. GPU SVM manages all necessary locking and unlocking
> > operations,
> > + * except for the recheck of the range's sequence number
> > + * (mmu_interval_read_retry) when the driver is committing GPU
> > bindings. This
> > + * lock corresponds to the 'driver->update' lock mentioned in the
> > HMM
> > + * documentation (TODO: Link). Future revisions may transition from
> > a GPU SVM
> > + * global lock to a per-notifier lock if finer-grained locking is
> > deemed
> > + * necessary.
> > + *
> > + * In addition to the locking mentioned above, the driver should
> > implement a
> > + * lock to safeguard core GPU SVM function calls that modify state,
> > such as
> > + * drm_gpusvm_range_find_or_insert and drm_gpusvm_range_remove.
> > Alternatively,
> > + * these core functions can be called within a single kernel thread,
> > for
> > + * instance, using an ordered work queue. This lock is denoted as
> > + * 'driver_svm_lock' in code examples.
> > + */
> > +
> > +/**
> > + * DOC: Migrataion
> > + *
> > + * The migration support is quite simple, allowing migration between
> > SRAM and
> > + * VRAM at the range granularity. For example, GPU SVM currently
> > does not
> > + * support mixing SRAM and VRAM pages within a range. This means
> > that upon GPU
> > + * fault, the entire range can be migrated to VRAM, and upon CPU
> > fault, the
> > + * entire range is migrated to SRAM.
> > + *
> > + * The reasoning for only supporting range granularity is as
> > follows: it
> > + * simplifies the implementation, and range sizes are driver-defined
> > and should
> > + * be relatively small.
> > + */
> > +
> > +/**
> > + * DOC: Partial Unmapping of Ranges
> > + *
> > + * Partial unmapping of ranges (e.g., 1M out of 2M is unmapped by
> > CPU resulting
> > + * in MMU_NOTIFY_UNMAP event) presents several challenges, with the
> > main one
> > + * being that a subset of the range still has CPU and GPU mappings.
> > If the
> > + * backing store for the range is in VRAM, a subset of the backing
> > store has
> > + * references. One option would be to split the range and VRAM
> > backing store,
> > + * but the implementation for this would be quite complicated. Given
> > that
> > + * partial unmappings are rare and driver-defined range sizes are
> > relatively
> > + * small, GPU SVM does not support splitting of ranges.
> > + *
> > + * With no support for range splitting, upon partial unmapping of a
> > range, the
> > + * driver is expected to invalidate and destroy the entire range. If
> > the range
> > + * has VRAM as its backing, the driver is also expected to migrate
> > any remaining
> > + * pages back to SRAM.
> > + */
> > +
> > +/**
> > + * DOC: Examples
> > + *
> > + * This section provides two examples of how to build the expected
> > driver
> > + * components: the GPU page fault handler and the garbage collector.
> > A third
> > + * example demonstrates a sample invalidation driver vfunc.
> > + *
> > + * The generic code provided does not include logic for complex
> > migration
> > + * policies, optimized invalidations, or other potentially required
> > driver
> > + * locking (e.g., DMA-resv locks).
> > + *
> > + * 1) GPU page fault handler
> > + *
> > + * int driver_bind_range(struct drm_gpusvm *gpusvm, struct
> > drm_gpusvm_range *range)
> > + * {
> > + * int err = 0;
> > + *
> > + * driver_alloc_and_setup_memory_for_bind(gpusvm,
> > range);
> > + *
> > + * drm_gpusvm_notifier_lock(gpusvm);
> > + * if (drm_gpusvm_range_pages_valid(range))
> > + * driver_commit_bind(gpusvm, range);
> > + * else
> > + * err = -EAGAIN;
> > + * drm_gpusvm_notifier_unlock(gpusvm);
> > + *
> > + * return err;
> > + * }
> > + *
> > + * int driver_gpu_fault(struct drm_gpusvm *gpusvm, u64
> > fault_addr,
> > + * u64 gpuva_start, u64 gpuva_end)
> > + * {
> > + * struct drm_gpusvm_ctx ctx = {};
> > + * int err;
> > + *
> > + * driver_svm_lock();
> > + * retry:
> > + * // Always process UNMAPs first so view of GPU SVM
> > ranges is current
> > + * driver_garbage_collector(gpusvm);
> > + *
> > + * range = drm_gpusvm_range_find_or_insert(gpusvm,
> > fault_addr,
> > + * gpuva_start,
> > gpuva_end,
> > + * &ctx);
> > + * if (IS_ERR(range)) {
> > + * err = PTR_ERR(range);
> > + * goto unlock;
> > + * }
> > + *
> > + * if (driver_migration_policy(range)) {
> > + * bo = driver_alloc_bo();
> > + * err = drm_gpusvm_migrate_to_vram(gpusvm,
> > range, bo, &ctx);
> > + * if (err) // CPU mappings may have
> > changed
> > + * goto retry;
> > + * }
> > + *
> > + * err = drm_gpusvm_range_get_pages(gpusvm, range,
> > &ctx);
> > + * if (err == -EFAULT || err == -EPERM) // CPU
> > mappings changed
> > + * goto retry;
> > + * else if (err)
> > + * goto unlock;
> > + *
> > + * err = driver_bind_range(gpusvm, range);
> > + * if (err == -EAGAIN) // CPU mappings changed
> > + * goto retry
> > + *
> > + * unlock:
> > + * driver_svm_unlock();
> > + * return err;
> > + * }
> > + *
> > + * 2) Garbage Collector.
> > + *
> > + * void __driver_garbage_collector(struct drm_gpusvm *gpusvm,
> > + * struct drm_gpusvm_range
> > *range)
> > + * {
> > + * struct drm_gpusvm_ctx ctx = {};
> > + *
> > + * assert_driver_svm_locked(gpusvm);
> > + *
> > + * // Partial unmap, migrate any remaining VRAM pages
> > back to SRAM
> > + * if (range->flags.partial_unmap)
> > + * drm_gpusvm_migrate_to_sram(gpusvm, range,
> > &ctx);
> > + *
> > + * driver_unbind_range(range);
> > + * drm_gpusvm_range_remove(gpusvm, range);
> > + * }
> > + *
> > + * void driver_garbage_collector(struct drm_gpusvm *gpusvm)
> > + * {
> > + * assert_driver_svm_locked(gpusvm);
> > + *
> > + * for_each_range_in_garbage_collector(gpusvm, range)
> > + * __driver_garbage_collector(gpusvm, range);
> > + * }
> > + *
> > + * 3) Invalidation driver vfunc.
> > + *
> > + * void driver_invalidation(struct drm_gpusvm *gpusvm,
> > + * struct drm_gpusvm_notifier
> > *notifier,
> > + * const struct mmu_notifier_range
> > *mmu_range)
> > + * {
> > + * struct drm_gpusvm_ctx ctx = { .in_notifier = true,
> > };
> > + * struct drm_gpusvm_range *range = NULL;
> > + *
> > + * driver_invalidate_device_tlb(gpusvm, mmu_range-
> > >start, mmu_range->end);
> > + *
> > + * drm_gpusvm_for_each_range(range, notifier,
> > mmu_range->start,
> > + * mmu_range->end) {
> > + * drm_gpusvm_range_unmap_pages(gpusvm, range,
> > &ctx);
> > + *
> > + * if (mmu_range->event != MMU_NOTIFY_UNMAP)
> > + * continue;
> > + *
> > + * drm_gpusvm_range_set_unmapped(range,
> > mmu_range);
> > + * driver_garbage_collector_add(gpusvm, range);
> > + * }
> > + * }
> > + */
> > +
> > +#define DRM_GPUSVM_RANGE_START(_range) ((_range)->va.start)
> > +#define DRM_GPUSVM_RANGE_END(_range) ((_range)->va.end - 1)
> > +INTERVAL_TREE_DEFINE(struct drm_gpusvm_range, rb.node, u64,
> > rb.__subtree_last,
> > + DRM_GPUSVM_RANGE_START, DRM_GPUSVM_RANGE_END,
> > + static __maybe_unused, range);
> > +
> > +#define DRM_GPUSVM_NOTIFIER_START(_notifier) ((_notifier)-
> > >interval.start)
> > +#define DRM_GPUSVM_NOTIFIER_END(_notifier) ((_notifier)-
> > >interval.end - 1)
> > +INTERVAL_TREE_DEFINE(struct drm_gpusvm_notifier, rb.node, u64,
> > + rb.__subtree_last, DRM_GPUSVM_NOTIFIER_START,
> > + DRM_GPUSVM_NOTIFIER_END, static __maybe_unused,
> > notifier);
> > +
> > +/**
> > + * npages_in_range() - Calculate the number of pages in a given
> > range
> > + * @start__: The start address of the range
> > + * @end__: The end address of the range
> > + *
> > + * This macro calculates the number of pages in a given memory
> > range,
> > + * specified by the start and end addresses. It divides the
> > difference
> > + * between the end and start addresses by the page size (PAGE_SIZE)
> > to
> > + * determine the number of pages in the range.
> > + *
> > + * Return: The number of pages in the specified range.
> > + */
> > +#define npages_in_range(start__, end__) \
> > + (((end__) - (start__)) >> PAGE_SHIFT)
> > +
> > +/**
> > + * struct drm_gpusvm_zdd - GPU SVM zone device data
> > + *
> > + * @refcount: Reference count for the zdd
> > + * @destroy_work: Work structure for asynchronous zdd destruction
> > + * @range: Pointer to the GPU SVM range
> > + * @vram_allocation: Driver-private pointer to the VRAM allocation
> > + *
> > + * This structure serves as a generic wrapper installed in
> > + * page->zone_device_data. It provides infrastructure for looking up
> > a range
> > + * upon CPU page fault and asynchronously releasing VRAM once the
> > CPU has no
> > + * page references. Asynchronous release is useful because CPU page
> > references
> > + * can be dropped in IRQ contexts, while releasing VRAM likely
> > requires sleeping
> > + * locks.
> > + */
> > +struct drm_gpusvm_zdd {
> > + struct kref refcount;
> > + struct work_struct destroy_work;
> > + struct drm_gpusvm_range *range;
> > + void *vram_allocation;
> > +};
> > +
> > +/**
> > + * drm_gpusvm_zdd_destroy_work_func - Work function for destroying a
> > zdd
> > + * @w: Pointer to the work_struct
> > + *
> > + * This function releases VRAM, puts GPU SVM range, and frees zdd.
> > + */
> > +static void drm_gpusvm_zdd_destroy_work_func(struct work_struct *w)
> > +{
> > + struct drm_gpusvm_zdd *zdd =
> > + container_of(w, struct drm_gpusvm_zdd,
> > destroy_work);
> > + struct drm_gpusvm_range *range = zdd->range;
> > + struct drm_gpusvm *gpusvm = range->gpusvm;
> > +
> > + if (gpusvm->ops->vram_release && zdd->vram_allocation)
> > + gpusvm->ops->vram_release(zdd->vram_allocation);
> > + drm_gpusvm_range_put(range);
> > + kfree(zdd);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_zdd_alloc - Allocate a zdd structure.
> > + * @range: Pointer to the GPU SVM range.
> > + *
> > + * This function allocates and initializes a new zdd structure. It
> > sets up the
> > + * reference count, initializes the destroy work, and links the
> > provided GPU SVM
> > + * range.
> > + *
> > + * Returns:
> > + * Pointer to the allocated zdd on success, ERR_PTR() on failure.
> > + */
> > +static struct drm_gpusvm_zdd *
> > +drm_gpusvm_zdd_alloc(struct drm_gpusvm_range *range)
> > +{
> > + struct drm_gpusvm_zdd *zdd;
> > +
> > + zdd = kmalloc(sizeof(*zdd), GFP_KERNEL);
> > + if (!zdd)
> > + return NULL;
> > +
> > + kref_init(&zdd->refcount);
> > + INIT_WORK(&zdd->destroy_work,
> > drm_gpusvm_zdd_destroy_work_func);
> > + zdd->range = drm_gpusvm_range_get(range);
> > + zdd->vram_allocation = NULL;
> > +
> > + return zdd;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_zdd_get - Get a reference to a zdd structure.
> > + * @zdd: Pointer to the zdd structure.
> > + *
> > + * This function increments the reference count of the provided zdd
> > structure.
> > + *
> > + * Returns: Pointer to the zdd structure.
> > + */
> > +static struct drm_gpusvm_zdd *drm_gpusvm_zdd_get(struct
> > drm_gpusvm_zdd *zdd)
> > +{
> > + kref_get(&zdd->refcount);
> > + return zdd;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_zdd_destroy - Destroy a zdd structure.
> > + * @ref: Pointer to the reference count structure.
> > + *
> > + * This function queues the destroy_work of the zdd for asynchronous
> > destruction.
> > + */
> > +static void drm_gpusvm_zdd_destroy(struct kref *ref)
> > +{
> > + struct drm_gpusvm_zdd *zdd =
> > + container_of(ref, struct drm_gpusvm_zdd, refcount);
> > + struct drm_gpusvm *gpusvm = zdd->range->gpusvm;
> > +
> > + queue_work(gpusvm->zdd_wq, &zdd->destroy_work);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_zdd_put - Put a zdd reference.
> > + * @zdd: Pointer to the zdd structure.
> > + *
> > + * This function decrements the reference count of the provided zdd
> > structure
> > + * and schedules its destruction if the count drops to zero.
> > + */
> > +static void drm_gpusvm_zdd_put(struct drm_gpusvm_zdd *zdd)
> > +{
> > + kref_put(&zdd->refcount, drm_gpusvm_zdd_destroy);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_find - Find GPU SVM range from GPU SVM notifier
> > + * @notifier: Pointer to the GPU SVM notifier structure.
> > + * @start: Start address of the range
> > + * @end: End address of the range
> > + *
> > + * Return: A pointer to the drm_gpusvm_range if found or NULL
> > + */
> > +struct drm_gpusvm_range *
> > +drm_gpusvm_range_find(struct drm_gpusvm_notifier *notifier, u64
> > start, u64 end)
> > +{
> > + return range_iter_first(¬ifier->root, start, end - 1);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_for_each_range_safe - Safely iterate over GPU SVM
> > ranges in a notifier
> > + * @range__: Iterator variable for the ranges
> > + * @next__: Iterator variable for the ranges temporay storage
> > + * @notifier__: Pointer to the GPU SVM notifier
> > + * @start__: Start address of the range
> > + * @end__: End address of the range
> > + *
> > + * This macro is used to iterate over GPU SVM ranges in a notifier
> > while
> > + * removing ranges from it.
> > + */
> > +#define drm_gpusvm_for_each_range_safe(range__, next__, notifier__,
> > start__, end__) \
> > + for ((range__) = drm_gpusvm_range_find((notifier__),
> > (start__), (end__)), \
> > + (next__) =
> > __drm_gpusvm_range_next(range__); \
> > + (range__) && (range__->va.start <
> > (end__)); \
> > + (range__) = (next__), (next__) =
> > __drm_gpusvm_range_next(range__))
> > +
> > +/**
> > + * __drm_gpusvm_notifier_next - get the next drm_gpusvm_notifier in
> > the list
> > + * @notifier: a pointer to the current drm_gpusvm_notifier
> > + *
> > + * Return: A pointer to the next drm_gpusvm_notifier if available,
> > or NULL if
> > + * the current notifier is the last one or if the input
> > notifier is
> > + * NULL.
> > + */
> > +static struct drm_gpusvm_notifier *
> > +__drm_gpusvm_notifier_next(struct drm_gpusvm_notifier *notifier)
> > +{
> > + if (notifier && !list_is_last(¬ifier->rb.entry,
> > + ¬ifier->gpusvm-
> > >notifier_list))
> > + return list_next_entry(notifier, rb.entry);
> > +
> > + return NULL;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_for_each_notifier - Iterate over GPU SVM notifiers in
> > a gpusvm
> > + * @notifier__: Iterator variable for the notifiers
> > + * @notifier__: Pointer to the GPU SVM notifier
> > + * @start__: Start address of the notifier
> > + * @end__: End address of the notifier
> > + *
> > + * This macro is used to iterate over GPU SVM notifiers in a gpusvm.
> > + */
> > +#define drm_gpusvm_for_each_notifier(notifier__, gpusvm__, start__,
> > end__) \
> > + for ((notifier__) = notifier_iter_first(&(gpusvm__)->root,
> > (start__), (end__) - 1); \
> > + (notifier__) && (notifier__->interval.start <
> > (end__)); \
> > + (notifier__) = __drm_gpusvm_notifier_next(notifier__))
> > +
> > +/**
> > + * drm_gpusvm_for_each_notifier_safe - Safely iterate over GPU SVM
> > notifiers in a gpusvm
> > + * @notifier__: Iterator variable for the notifiers
> > + * @next__: Iterator variable for the notifiers temporay storage
> > + * @notifier__: Pointer to the GPU SVM notifier
> > + * @start__: Start address of the notifier
> > + * @end__: End address of the notifier
> > + *
> > + * This macro is used to iterate over GPU SVM notifiers in a gpusvm
> > while
> > + * removing notifiers from it.
> > + */
> > +#define drm_gpusvm_for_each_notifier_safe(notifier__, next__,
> > gpusvm__, start__, end__) \
> > + for ((notifier__) = notifier_iter_first(&(gpusvm__)->root,
> > (start__), (end__) - 1), \
> > + (next__) =
> > __drm_gpusvm_notifier_next(notifier__); \
> > + (notifier__) && (notifier__->interval.start <
> > (end__)); \
> > + (notifier__) = (next__), (next__) =
> > __drm_gpusvm_notifier_next(notifier__))
> > +
> > +/**
> > + * drm_gpusvm_notifier_invalidate - Invalidate a GPU SVM notifier.
> > + * @mni: Pointer to the mmu_interval_notifier structure.
> > + * @mmu_range: Pointer to the mmu_notifier_range structure.
> > + * @cur_seq: Current sequence number.
> > + *
> > + * This function serves as a generic MMU notifier for GPU SVM. It
> > sets the MMU
> > + * notifier sequence number and calls the driver invalidate vfunc
> > under
> > + * gpusvm->notifier_lock.
> > + *
> > + * Returns:
> > + * true if the operation succeeds, false otherwise.
> > + */
> > +static bool
> > +drm_gpusvm_notifier_invalidate(struct mmu_interval_notifier *mni,
> > + const struct mmu_notifier_range
> > *mmu_range,
> > + unsigned long cur_seq)
> > +{
> > + struct drm_gpusvm_notifier *notifier =
> > + container_of(mni, typeof(*notifier), notifier);
> > + struct drm_gpusvm *gpusvm = notifier->gpusvm;
> > +
> > + if (!mmu_notifier_range_blockable(mmu_range))
> > + return false;
> > +
> > + down_write(&gpusvm->notifier_lock);
> > + mmu_interval_set_seq(mni, cur_seq);
> > + gpusvm->ops->invalidate(gpusvm, notifier, mmu_range);
> > + up_write(&gpusvm->notifier_lock);
> > +
> > + return true;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_notifier_ops - MMU interval notifier operations for
> > GPU SVM
> > + */
> > +static const struct mmu_interval_notifier_ops
> > drm_gpusvm_notifier_ops = {
> > + .invalidate = drm_gpusvm_notifier_invalidate,
> > +};
> > +
> > +/**
> > + * drm_gpusvm_init - Initialize the GPU SVM.
> > + * @gpusvm: Pointer to the GPU SVM structure.
> > + * @name: Name of the GPU SVM.
> > + * @drm: Pointer to the DRM device structure.
> > + * @mm: Pointer to the mm_struct for the address space.
> > + * @device_private_page_owner: Device private pages owner.
> > + * @mm_start: Start address of GPU SVM.
> > + * @mm_range: Range of the GPU SVM.
> > + * @notifier_size: Size of individual notifiers.
> > + * @ops: Pointer to the operations structure for GPU SVM.
> > + * @chunk_sizes: Pointer to the array of chunk sizes used in range
> > allocation.
> > + * Entries should be powers of 2 in descending order
> > with last
> > + * entry being SZ_4K.
> > + * @num_chunks: Number of chunks.
> > + *
> > + * This function initializes the GPU SVM.
> > + *
> > + * Returns:
> > + * 0 on success, a negative error code on failure.
> > + */
> > +int drm_gpusvm_init(struct drm_gpusvm *gpusvm,
> > + const char *name, struct drm_device *drm,
> > + struct mm_struct *mm, void
> > *device_private_page_owner,
> > + u64 mm_start, u64 mm_range, u64 notifier_size,
> > + const struct drm_gpusvm_ops *ops,
> > + const u64 *chunk_sizes, int num_chunks)
> > +{
> > + if (!ops->invalidate || !num_chunks)
> > + return -EINVAL;
> > +
> > + gpusvm->name = name;
> > + gpusvm->drm = drm;
> > + gpusvm->mm = mm;
> > + gpusvm->device_private_page_owner =
> > device_private_page_owner;
> > + gpusvm->mm_start = mm_start;
> > + gpusvm->mm_range = mm_range;
> > + gpusvm->notifier_size = notifier_size;
> > + gpusvm->ops = ops;
> > + gpusvm->chunk_sizes = chunk_sizes;
> > + gpusvm->num_chunks = num_chunks;
> > + gpusvm->zdd_wq = system_wq;
> > +
> > + mmgrab(mm);
> > + gpusvm->root = RB_ROOT_CACHED;
> > + INIT_LIST_HEAD(&gpusvm->notifier_list);
> > +
> > + init_rwsem(&gpusvm->notifier_lock);
> > +
> > + fs_reclaim_acquire(GFP_KERNEL);
> > + might_lock(&gpusvm->notifier_lock);
> > + fs_reclaim_release(GFP_KERNEL);
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_notifier_find - Find GPU SVM notifier
> > + * @gpusvm__: Pointer to the GPU SVM structure
> > + * @fault_addr__: Fault address
> > + *
> > + * This macro finds the GPU SVM notifier associated with the fault
> > address.
> > + *
> > + * Returns:
> > + * Pointer to the GPU SVM notifier on success, NULL otherwise.
> > + */
> > +#define drm_gpusvm_notifier_find(gpusvm__, fault_addr__) \
> > + notifier_iter_first(&(gpusvm__)->root, (fault_addr__), \
> > + (fault_addr__ + 1))
> > +
> > +/**
> > + * to_drm_gpusvm_notifier - retrieve the container struct for a
> > given rbtree node
> > + * @node__: a pointer to the rbtree node embedded within a
> > drm_gpusvm_notifier struct
> > + *
> > + * Return: A pointer to the containing drm_gpusvm_notifier
> > structure.
> > + */
> > +#define to_drm_gpusvm_notifier(__node) \
> > + container_of((__node), struct drm_gpusvm_notifier, rb.node)
> > +
> > +/**
> > + * drm_gpusvm_notifier_insert - Insert GPU SVM notifier
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @notifier: Pointer to the GPU SVM notifier structure
> > + *
> > + * This function inserts the GPU SVM notifier into the GPU SVM RB
> > tree and list.
> > + */
> > +static void drm_gpusvm_notifier_insert(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_notifier
> > *notifier)
> > +{
> > + struct rb_node *node;
> > + struct list_head *head;
> > +
> > + notifier_insert(notifier, &gpusvm->root);
> > +
> > + node = rb_prev(¬ifier->rb.node);
> > + if (node)
> > + head = &(to_drm_gpusvm_notifier(node))->rb.entry;
> > + else
> > + head = &gpusvm->notifier_list;
> > +
> > + list_add(¬ifier->rb.entry, head);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_notifier_remove - Remove GPU SVM notifier
> > + * @gpusvm__: Pointer to the GPU SVM tructure
> > + * @notifier__: Pointer to the GPU SVM notifier structure
> > + *
> > + * This macro removes the GPU SVM notifier from the GPU SVM RB tree
> > and list.
> > + */
> > +#define drm_gpusvm_notifier_remove(gpusvm__, notifier__) \
> > + notifier_remove((notifier__), &(gpusvm__)->root); \
> > + list_del(&(notifier__)->rb.entry)
> > +
> > +/**
> > + * drm_gpusvm_fini - Finalize the GPU SVM.
> > + * @gpusvm: Pointer to the GPU SVM structure.
> > + *
> > + * This function finalizes the GPU SVM by cleaning up any remaining
> > ranges and
> > + * notifiers, and dropping a reference to struct MM.
> > + */
> > +void drm_gpusvm_fini(struct drm_gpusvm *gpusvm)
> > +{
> > + struct drm_gpusvm_notifier *notifier, *next;
> > +
> > + drm_gpusvm_for_each_notifier_safe(notifier, next, gpusvm, 0,
> > LONG_MAX) {
> > + struct drm_gpusvm_range *range, *__next;
> > +
> > + /*
> > + * Remove notifier first to avoid racing with any
> > invalidation
> > + */
> > + mmu_interval_notifier_remove(¬ifier->notifier);
> > + notifier->flags.removed = true;
> > +
> > + drm_gpusvm_for_each_range_safe(range, __next,
> > notifier, 0,
> > + LONG_MAX)
> > + drm_gpusvm_range_remove(gpusvm, range);
> > + }
> > +
> > + mmdrop(gpusvm->mm);
> > + WARN_ON(!RB_EMPTY_ROOT(&gpusvm->root.rb_root));
> > +}
> > +
> > +/**
> > + * drm_gpusvm_notifier_alloc - Allocate GPU SVM notifier
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @fault_addr: Fault address
> > + *
> > + * This function allocates and initializes the GPU SVM notifier
> > structure.
> > + *
> > + * Returns:
> > + * Pointer to the allocated GPU SVM notifier on success, ERR_PTR()
> > on failure.
> > + */
> > +static struct drm_gpusvm_notifier *
> > +drm_gpusvm_notifier_alloc(struct drm_gpusvm *gpusvm, u64 fault_addr)
> > +{
> > + struct drm_gpusvm_notifier *notifier;
> > +
> > + if (gpusvm->ops->notifier_alloc)
> > + notifier = gpusvm->ops->notifier_alloc();
> > + else
> > + notifier = kzalloc(sizeof(*notifier), GFP_KERNEL);
> > +
> > + if (!notifier)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + notifier->gpusvm = gpusvm;
> > + notifier->interval.start = ALIGN_DOWN(fault_addr, gpusvm-
> > >notifier_size);
> > + notifier->interval.end = ALIGN(fault_addr + 1, gpusvm-
> > >notifier_size);
> > + INIT_LIST_HEAD(¬ifier->rb.entry);
> > + notifier->root = RB_ROOT_CACHED;
> > + INIT_LIST_HEAD(¬ifier->range_list);
> > +
> > + return notifier;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_notifier_free - Free GPU SVM notifier
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @notifier: Pointer to the GPU SVM notifier structure
> > + *
> > + * This function frees the GPU SVM notifier structure.
> > + */
> > +static void drm_gpusvm_notifier_free(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_notifier
> > *notifier)
> > +{
> > + WARN_ON(!RB_EMPTY_ROOT(¬ifier->root.rb_root));
> > +
> > + if (gpusvm->ops->notifier_free)
> > + gpusvm->ops->notifier_free(notifier);
> > + else
> > + kfree(notifier);
> > +}
> > +
> > +/**
> > + * to_drm_gpusvm_range - retrieve the container struct for a given
> > rbtree node
> > + * @node__: a pointer to the rbtree node embedded within a
> > drm_gpusvm_range struct
> > + *
> > + * Return: A pointer to the containing drm_gpusvm_range structure.
> > + */
> > +#define to_drm_gpusvm_range(node__) \
> > + container_of((node__), struct drm_gpusvm_range, rb.node)
> > +
> > +/**
> > + * drm_gpusvm_range_insert - Insert GPU SVM range
> > + * @notifier: Pointer to the GPU SVM notifier structure
> > + * @range: Pointer to the GPU SVM range structure
> > + *
> > + * This function inserts the GPU SVM range into the notifier RB tree
> > and list.
> > + */
> > +static void drm_gpusvm_range_insert(struct drm_gpusvm_notifier
> > *notifier,
> > + struct drm_gpusvm_range *range)
> > +{
> > + struct rb_node *node;
> > + struct list_head *head;
> > +
> > + drm_gpusvm_notifier_lock(notifier->gpusvm);
> > + range_insert(range, ¬ifier->root);
> > +
> > + node = rb_prev(&range->rb.node);
> > + if (node)
> > + head = &(to_drm_gpusvm_range(node))->rb.entry;
> > + else
> > + head = ¬ifier->range_list;
> > +
> > + list_add(&range->rb.entry, head);
> > + drm_gpusvm_notifier_unlock(notifier->gpusvm);
> > +}
> > +
> > +/**
> > + * __drm_gpusvm_range_remove - Remove GPU SVM range
> > + * @notifier__: Pointer to the GPU SVM notifier structure
> > + * @range__: Pointer to the GPU SVM range structure
> > + *
> > + * This macro removes the GPU SVM range from the notifier RB tree
> > and list.
> > + */
> > +#define __drm_gpusvm_range_remove(notifier__, range__) \
> > + range_remove((range__), &(notifier__)->root); \
> > + list_del(&(range__)->rb.entry)
> > +
> > +/**
> > + * drm_gpusvm_range_alloc - Allocate GPU SVM range
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @notifier: Pointer to the GPU SVM notifier structure
> > + * @fault_addr: Fault address
> > + * @chunk_size: Chunk size
> > + * @migrate_vram: Flag indicating whether to migrate VRAM
> > + *
> > + * This function allocates and initializes the GPU SVM range
> > structure.
> > + *
> > + * Returns:
> > + * Pointer to the allocated GPU SVM range on success, ERR_PTR() on
> > failure.
> > + */
> > +static struct drm_gpusvm_range *
> > +drm_gpusvm_range_alloc(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_notifier *notifier,
> > + u64 fault_addr, u64 chunk_size, bool
> > migrate_vram)
> > +{
> > + struct drm_gpusvm_range *range;
> > +
> > + if (gpusvm->ops->range_alloc)
> > + range = gpusvm->ops->range_alloc(gpusvm);
> > + else
> > + range = kzalloc(sizeof(*range), GFP_KERNEL);
> > +
> > + if (!range)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + kref_init(&range->refcount);
> > + range->gpusvm = gpusvm;
> > + range->notifier = notifier;
> > + range->va.start = ALIGN_DOWN(fault_addr, chunk_size);
> > + range->va.end = ALIGN(fault_addr + 1, chunk_size);
> > + INIT_LIST_HEAD(&range->rb.entry);
> > + range->notifier_seq = LONG_MAX;
> > + range->flags.migrate_vram = migrate_vram ? 1 : 0;
> > +
> > + return range;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_check_pages - Check pages
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @notifier: Pointer to the GPU SVM notifier structure
> > + * @start: Start address
> > + * @end: End address
> > + *
> > + * Check if pages between start and end have been faulted in on the
> > CPU. Use to
> > + * prevent migration of pages without CPU backing store.
> > + *
> > + * Returns:
> > + * True if pages have been faulted into CPU, False otherwise
> > + */
> > +static bool drm_gpusvm_check_pages(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_notifier
> > *notifier,
> > + u64 start, u64 end)
> > +{
> > + struct hmm_range hmm_range = {
> > + .default_flags = 0,
> > + .notifier = ¬ifier->notifier,
> > + .start = start,
> > + .end = end,
> > + .dev_private_owner = gpusvm-
> > >device_private_page_owner,
> > + };
> > + unsigned long timeout =
> > + jiffies +
> > msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> > + unsigned long *pfns;
> > + unsigned long npages = npages_in_range(start, end);
> > + int err, i;
> > +
> > + mmap_assert_locked(gpusvm->mm);
> > +
> > + pfns = kvmalloc_array(npages, sizeof(*pfns), GFP_KERNEL);
> > + if (!pfns)
> > + return false;
> > +
> > + hmm_range.notifier_seq = mmu_interval_read_begin(¬ifier-
> > >notifier);
> > + hmm_range.hmm_pfns = pfns;
> > +
> > + while (true) {
> > + err = hmm_range_fault(&hmm_range);
> > + if (err == -EBUSY) {
> > + if (time_after(jiffies, timeout))
> > + break;
> > +
> > + hmm_range.notifier_seq =
> > mmu_interval_read_begin(¬ifier->notifier);
> > + continue;
> > + }
> > + break;
> > + }
> > + if (err)
> > + goto err_free;
> > +
> > + for (i = 0; i < npages; ++i) {
> > + if (!(pfns[i] & HMM_PFN_VALID)) {
> > + err = -EFAULT;
> > + goto err_free;
> > + }
> > + }
> > +
> > +err_free:
> > + kvfree(pfns);
> > + return err ? false : true;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_chunk_size - Determine chunk size for GPU SVM
> > range
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @notifier: Pointer to the GPU SVM notifier structure
> > + * @vas: Pointer to the virtual memory area structure
> > + * @fault_addr: Fault address
> > + * @gpuva_start: Start address of GPUVA which mirrors CPU
> > + * @gpuva_end: End address of GPUVA which mirrors CPU
> > + * @check_pages: Flag indicating whether to check pages
> > + *
> > + * This function determines the chunk size for the GPU SVM range
> > based on the
> > + * fault address, GPU SVM chunk sizes, existing GPU SVM ranges, and
> > the virtual
> > + * memory area boundaries.
> > + *
> > + * Returns:
> > + * Chunk size on success, LONG_MAX on failure.
> > + */
> > +static u64 drm_gpusvm_range_chunk_size(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_notifier
> > *notifier,
> > + struct vm_area_struct *vas,
> > + u64 fault_addr, u64
> > gpuva_start,
> > + u64 gpuva_end, bool
> > check_pages)
> > +{
> > + u64 start, end;
> > + int i = 0;
> > +
> > +retry:
> > + for (; i < gpusvm->num_chunks; ++i) {
> > + start = ALIGN_DOWN(fault_addr, gpusvm-
> > >chunk_sizes[i]);
> > + end = ALIGN(fault_addr + 1, gpusvm->chunk_sizes[i]);
> > +
> > + if (start >= vas->vm_start && end <= vas->vm_end &&
> > + start >= notifier->interval.start &&
> > + end <= notifier->interval.end &&
> > + start >= gpuva_start && end <= gpuva_end)
> > + break;
> > + }
> > +
> > + if (i == gpusvm->num_chunks)
> > + return LONG_MAX;
> > +
> > + /*
> > + * If allocation more than page, ensure not to overlap with
> > existing
> > + * ranges.
> > + */
> > + if (end - start != SZ_4K) {
> > + struct drm_gpusvm_range *range;
> > +
> > + range = drm_gpusvm_range_find(notifier, start, end);
> > + if (range) {
> > + ++i;
> > + goto retry;
> > + }
> > +
> > + /*
> > + * XXX: Only create range on pages CPU has faulted
> > in. Without
> > + * this check, or prefault, on BMG
> > 'xe_exec_system_allocator --r
> > + * process-many-malloc' fails. In the failure case,
> > each process
> > + * mallocs 16k but the CPU VMA is ~128k which
> > results in 64k SVM
> > + * ranges. When migrating the SVM ranges, some
> > processes fail in
> > + * drm_gpusvm_migrate_to_vram with 'migrate.cpages
> > != npages'
> > + * and then upon drm_gpusvm_range_get_pages device
> > pages from
> > + * other processes are collected + faulted in which
> > creates all
> > + * sorts of problems. Unsure exactly how this
> > happening, also
> > + * problem goes away if 'xe_exec_system_allocator --
> > r
> > + * process-many-malloc' mallocs at least 64k at a
> > time.
> > + */
> > + if (check_pages &&
> > + !drm_gpusvm_check_pages(gpusvm, notifier, start,
> > end)) {
> > + ++i;
> > + goto retry;
> > + }
> > + }
> > +
> > + return end - start;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_find_or_insert - Find or insert GPU SVM range
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @fault_addr: Fault address
> > + * @gpuva_start: Start address of GPUVA which mirrors CPU
> > + * @gpuva_end: End address of GPUVA which mirrors CPU
> > + * @ctx: GPU SVM context
> > + *
> > + * This function finds or inserts a newly allocated a GPU SVM range
> > based on the
> > + * fault address. Caller must hold a lock to protect range lookup
> > and insertion.
> > + *
> > + * Returns:
> > + * Pointer to the GPU SVM range on success, ERR_PTR() on failure.
> > + */
> > +struct drm_gpusvm_range *
> > +drm_gpusvm_range_find_or_insert(struct drm_gpusvm *gpusvm, u64
> > fault_addr,
> > + u64 gpuva_start, u64 gpuva_end,
> > + const struct drm_gpusvm_ctx *ctx)
> > +{
> > + struct drm_gpusvm_notifier *notifier;
> > + struct drm_gpusvm_range *range;
> > + struct mm_struct *mm = gpusvm->mm;
> > + struct vm_area_struct *vas;
> > + bool notifier_alloc = false;
> > + u64 chunk_size;
> > + int err;
> > + bool migrate_vram;
> > +
> > + if (fault_addr < gpusvm->mm_start ||
> > + fault_addr > gpusvm->mm_start + gpusvm->mm_range) {
> > + err = -EINVAL;
> > + goto err_out;
> > + }
> > +
> > + if (!ctx->mmap_locked) {
> > + if (!mmget_not_zero(mm)) {
> > + err = -EFAULT;
> > + goto err_out;
> > + }
> > + mmap_write_lock(mm);
> > + }
> > +
> > + mmap_assert_write_locked(mm);
> > +
> > + notifier = drm_gpusvm_notifier_find(gpusvm, fault_addr);
> > + if (!notifier) {
> > + notifier = drm_gpusvm_notifier_alloc(gpusvm,
> > fault_addr);
> > + if (IS_ERR(notifier)) {
> > + err = PTR_ERR(notifier);
> > + goto err_mmunlock;
> > + }
> > + notifier_alloc = true;
> > + err = mmu_interval_notifier_insert_locked(¬ifier-
> > >notifier,
> > + mm,
> > notifier->interval.start,
> > + notifier-
> > >interval.end -
> > + notifier-
> > >interval.start,
> > +
> > &drm_gpusvm_notifier_ops);
> > + if (err)
> > + goto err_notifier;
> > + }
> > +
> > + vas = vma_lookup(mm, fault_addr);
> > + if (!vas) {
> > + err = -ENOENT;
> > + goto err_notifier_remove;
> > + }
> > +
> > + if (!ctx->read_only && !(vas->vm_flags & VM_WRITE)) {
> > + err = -EPERM;
> > + goto err_notifier_remove;
> > + }
> > +
> > + range = drm_gpusvm_range_find(notifier, fault_addr,
> > fault_addr + 1);
> > + if (range)
> > + goto out_mmunlock;
> > + /*
> > + * XXX: Short-circuiting migration based on migrate_vma_*
> > current
> > + * limitations. If/when migrate_vma_* add more support, this
> > logic will
> > + * have to change.
> > + */
> > + migrate_vram = ctx->vram_possible &&
> > + vma_is_anonymous(vas) && !is_vm_hugetlb_page(vas);
> > +
> > + chunk_size = drm_gpusvm_range_chunk_size(gpusvm, notifier,
> > vas,
> > + fault_addr,
> > gpuva_start,
> > + gpuva_end,
> > migrate_vram &&
> > + !ctx->prefault);
> > + if (chunk_size == LONG_MAX) {
> > + err = -EINVAL;
> > + goto err_notifier_remove;
> > + }
> > +
> > + range = drm_gpusvm_range_alloc(gpusvm, notifier, fault_addr,
> > chunk_size,
> > + migrate_vram);
> > + if (IS_ERR(range)) {
> > + err = PTR_ERR(range);
> > + goto err_notifier_remove;
> > + }
> > +
> > + drm_gpusvm_range_insert(notifier, range);
> > + if (notifier_alloc)
> > + drm_gpusvm_notifier_insert(gpusvm, notifier);
> > +
> > + if (ctx->prefault) {
> > + struct drm_gpusvm_ctx __ctx = *ctx;
> > +
> > + __ctx.mmap_locked = true;
> > + err = drm_gpusvm_range_get_pages(gpusvm, range,
> > &__ctx);
> > + if (err)
> > + goto err_range_remove;
> > + }
> > +
> > +out_mmunlock:
> > + if (!ctx->mmap_locked) {
> > + mmap_write_unlock(mm);
> > + mmput(mm);
> > + }
> > +
> > + return range;
> > +
> > +err_range_remove:
> > + __drm_gpusvm_range_remove(notifier, range);
> > +err_notifier_remove:
> > + if (notifier_alloc)
> > + mmu_interval_notifier_remove(¬ifier->notifier);
> > +err_notifier:
> > + if (notifier_alloc)
> > + drm_gpusvm_notifier_free(gpusvm, notifier);
> > +err_mmunlock:
> > + if (!ctx->mmap_locked) {
> > + mmap_write_unlock(mm);
> > + mmput(mm);
> > + }
> > +err_out:
> > + return ERR_PTR(err);
> > +}
> > +
> > +/**
> > + * for_each_dma_page - iterate over pages in a DMA regio`n
> > + * @i__: the current page index in the iteration
> > + * @j__: the current page index, log order, in the iteration
> > + * @npages__: the total number of pages in the DMA region
> > + * @order__: the order of the pages in the DMA region
> > + *
> > + * This macro iterates over each page in a DMA region. The DMA
> > region
> > + * is assumed to be composed of 2^@order__ pages, and the macro will
> > + * step through the region one block of 2^@order__ pages at a time.
> > + */
> > +#define for_each_dma_page(i__, j__, npages__, order__) \
> > + for ((i__) = 0, (j__) = 0; (i__) < (npages__); \
> > + (j__)++, (i__) += 0x1 << (order__))
> > +
> > +/**
> > + * __drm_gpusvm_range_unmap_pages - Unmap pages associated with a
> > GPU SVM range (internal)
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + *
> > + * This function unmap pages associated with a GPU SVM range.
> > Assumes and
> > + * asserts correct locking is in place when called.
> > + */
> > +static void __drm_gpusvm_range_unmap_pages(struct drm_gpusvm
> > *gpusvm,
> > + struct drm_gpusvm_range
> > *range)
> > +{
> > + lockdep_assert_held(&gpusvm->notifier_lock);
> > +
> > + if (range->pages) {
> > + unsigned long i, j, npages = npages_in_range(range-
> > >va.start,
> > + range-
> > >va.end);
> > +
> > + if (range->flags.has_dma_mapping) {
> > + for_each_dma_page(i, j, npages, range-
> > >order)
> > + dma_unmap_page(gpusvm->drm->dev,
> > + range->dma_addr[j],
> > + PAGE_SIZE << range-
> > >order,
> > + DMA_BIDIRECTIONAL);
> > + }
> > +
> > + range->flags.has_vram_pages = false;
> > + range->flags.has_dma_mapping = false;
> > + }
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_free_pages - Free pages associated with a GPU
> > SVM range
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + *
> > + * This function free pages associated with a GPU SVM range.
> > + */
> > +static void drm_gpusvm_range_free_pages(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range
> > *range)
> > +{
> > + lockdep_assert_held(&gpusvm->notifier_lock);
> > +
> > + if (range->pages) {
> > + if (range->flags.kfree_mapping) {
> > + kfree(range->dma_addr);
> > + range->flags.kfree_mapping = false;
> > + range->pages = NULL;
> > + } else {
> > + kvfree(range->pages);
> > + range->pages = NULL;
> > + }
> > + }
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_remove - Remove GPU SVM range
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range to be removed
> > + *
> > + * This function removes the specified GPU SVM range and also
> > removes the parent
> > + * GPU SVM notifier if no more ranges remain in the notifier. The
> > caller must
> > + * hold a lock to protect range and notifier removal.
> > + */
> > +void drm_gpusvm_range_remove(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range)
> > +{
> > + struct drm_gpusvm_notifier *notifier;
> > +
> > + notifier = drm_gpusvm_notifier_find(gpusvm, range-
> > >va.start);
> > + if (WARN_ON_ONCE(!notifier))
> > + return;
> > +
> > + drm_gpusvm_notifier_lock(gpusvm);
> > + __drm_gpusvm_range_unmap_pages(gpusvm, range);
> > + drm_gpusvm_range_free_pages(gpusvm, range);
> > + __drm_gpusvm_range_remove(notifier, range);
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > +
> > + drm_gpusvm_range_put(range);
> > +
> > + if (RB_EMPTY_ROOT(¬ifier->root.rb_root)) {
> > + if (!notifier->flags.removed)
> > + mmu_interval_notifier_remove(¬ifier-
> > >notifier);
> > + drm_gpusvm_notifier_remove(gpusvm, notifier);
> > + drm_gpusvm_notifier_free(gpusvm, notifier);
> > + }
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_get - Get a reference to GPU SVM range
> > + * @range: Pointer to the GPU SVM range
> > + *
> > + * This function increments the reference count of the specified GPU
> > SVM range.
> > + *
> > + * Returns:
> > + * Pointer to the GPU SVM range.
> > + */
> > +struct drm_gpusvm_range *
> > +drm_gpusvm_range_get(struct drm_gpusvm_range *range)
> > +{
> > + kref_get(&range->refcount);
> > +
> > + return range;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_destroy - Destroy GPU SVM range
> > + * @refcount: Pointer to the reference counter embedded in the GPU
> > SVM range
> > + *
> > + * This function destroys the specified GPU SVM range when its
> > reference count
> > + * reaches zero. If a custom range-free function is provided, it is
> > invoked to
> > + * free the range; otherwise, the range is deallocated using
> > kfree().
> > + */
> > +static void drm_gpusvm_range_destroy(struct kref *refcount)
> > +{
> > + struct drm_gpusvm_range *range =
> > + container_of(refcount, struct drm_gpusvm_range,
> > refcount);
> > + struct drm_gpusvm *gpusvm = range->gpusvm;
> > +
> > + if (gpusvm->ops->range_free)
> > + gpusvm->ops->range_free(range);
> > + else
> > + kfree(range);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_put - Put a reference to GPU SVM range
> > + * @range: Pointer to the GPU SVM range
> > + *
> > + * This function decrements the reference count of the specified GPU
> > SVM range
> > + * and frees it when the count reaches zero.
> > + */
> > +void drm_gpusvm_range_put(struct drm_gpusvm_range *range)
> > +{
> > + kref_put(&range->refcount, drm_gpusvm_range_destroy);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_pages_valid - GPU SVM range pages valid
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + *
> > + * This function determines if a GPU SVM range pages are valid.
> > Expected be
> > + * called holding gpusvm->notifier_lock and as the last step before
> > commiting a
> > + * GPU binding.
> > + *
> > + * Returns:
> > + * True if GPU SVM range has valid pages, False otherwise
> > + */
> > +bool drm_gpusvm_range_pages_valid(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range)
> > +{
> > + lockdep_assert_held(&gpusvm->notifier_lock);
> > +
> > + return range->flags.has_vram_pages || range-
> > >flags.has_dma_mapping;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_pages_valid_unlocked - GPU SVM range pages valid
> > unlocked
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + *
> > + * This function determines if a GPU SVM range pages are valid.
> > Expected be
> > + * called without holding gpusvm->notifier_lock.
> > + *
> > + * Returns:
> > + * True if GPU SVM range has valid pages, False otherwise
> > + */
> > +static bool
> > +drm_gpusvm_range_pages_valid_unlocked(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range
> > *range)
> > +{
> > + bool pages_valid;
> > +
> > + if (!range->pages)
> > + return false;
> > +
> > + drm_gpusvm_notifier_lock(gpusvm);
> > + pages_valid = drm_gpusvm_range_pages_valid(gpusvm, range);
> > + if (!pages_valid && range->flags.kfree_mapping) {
> > + kfree(range->dma_addr);
> > + range->flags.kfree_mapping = false;
> > + range->pages = NULL;
> > + }
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > +
> > + return pages_valid;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_get_pages - Get pages for a GPU SVM range
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + * @ctx: GPU SVM context
> > + *
> > + * This function gets pages for a GPU SVM range and ensures they are
> > mapped for
> > + * DMA access.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure.
> > + */
> > +int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range,
> > + const struct drm_gpusvm_ctx *ctx)
> > +{
> > + struct mmu_interval_notifier *notifier = &range->notifier-
> > >notifier;
> > + struct hmm_range hmm_range = {
> > + .default_flags = HMM_PFN_REQ_FAULT | (ctx->read_only
> > ? 0 :
> > + HMM_PFN_REQ_WRITE),
> > + .notifier = notifier,
> > + .start = range->va.start,
> > + .end = range->va.end,
> > + .dev_private_owner = gpusvm-
> > >device_private_page_owner,
> > + };
> > + struct mm_struct *mm = gpusvm->mm;
> > + unsigned long timeout =
> > + jiffies +
> > msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> > + unsigned long i, j;
> > + unsigned long npages = npages_in_range(range->va.start,
> > range->va.end);
> > + unsigned int order = 0;
> > + unsigned long *pfns;
> > + struct page **pages;
> > + int err = 0;
> > + bool vram_pages = !!range->flags.migrate_vram;
> > + bool alloc_pfns = false, kfree_mapping;
> > +
> > +retry:
> > + kfree_mapping = false;
> > + hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
> > + if (drm_gpusvm_range_pages_valid_unlocked(gpusvm, range))
> > + return 0;
> > +
> > + if (range->notifier_seq == hmm_range.notifier_seq && range-
> > >pages) {
> > + if (ctx->prefault)
> > + return 0;
> > +
> > + pfns = (unsigned long *)range->pages;
> > + pages = range->pages;
> > + goto map_pages;
> > + }
> > +
> > + if (!range->pages) {
> > + pfns = kvmalloc_array(npages, sizeof(*pfns),
> > GFP_KERNEL);
> > + if (!pfns)
> > + return -ENOMEM;
> > + alloc_pfns = true;
> > + } else {
> > + pfns = (unsigned long *)range->pages;
> > + }
> > +
> > + if (!ctx->mmap_locked) {
> > + if (!mmget_not_zero(mm)) {
> > + err = -EFAULT;
> > + goto err_out;
> > + }
> > + }
> > +
> > + hmm_range.hmm_pfns = pfns;
> > + while (true) {
> > + /* Must be checked after mmu_interval_read_begin */
> > + if (range->flags.unmapped) {
> > + err = -EFAULT;
> > + break;
> > + }
> > +
> > + if (!ctx->mmap_locked) {
> > + /*
> > + * XXX: HMM locking document indicates only
> > a read-lock
> > + * is required but there apears to be a
> > window between
> > + * the MMU_NOTIFY_MIGRATE event triggered in
> > a CPU fault
> > + * via migrate_vma_setup and the pages
> > actually moving
> > + * in migrate_vma_finalize in which this
> > code can grab
> > + * garbage pages. Grabbing the write-lock if
> > the range
> > + * is attached to vram appears to protect
> > against this
> > + * race.
> > + */
> > + if (vram_pages)
> > + mmap_write_lock(mm);
> > + else
> > + mmap_read_lock(mm);
> > + }
> > + err = hmm_range_fault(&hmm_range);
> > + if (!ctx->mmap_locked) {
> > + if (vram_pages)
> > + mmap_write_unlock(mm);
> > + else
> > + mmap_read_unlock(mm);
> > + }
> > +
> > + if (err == -EBUSY) {
> > + if (time_after(jiffies, timeout))
> > + break;
> > +
> > + hmm_range.notifier_seq =
> > mmu_interval_read_begin(notifier);
> > + continue;
> > + }
> > + break;
> > + }
> > + if (!ctx->mmap_locked)
> > + mmput(mm);
> > + if (err)
> > + goto err_free;
> > +
> > + pages = (struct page **)pfns;
> > +
> > + if (ctx->prefault) {
> > + range->pages = pages;
> > + goto set_seqno;
> > + }
> > +
> > +map_pages:
> > + if (is_device_private_page(hmm_pfn_to_page(pfns[0]))) {
> > + WARN_ON_ONCE(!range->vram_allocation);
> > +
> > + for (i = 0; i < npages; ++i) {
> > + pages[i] = hmm_pfn_to_page(pfns[i]);
> > +
> > + if
> > (WARN_ON_ONCE(!is_device_private_page(pages[i]))) {
> > + err = -EOPNOTSUPP;
> > + goto err_free;
> > + }
> > + }
> > +
> > + /* Do not race with notifier unmapping pages */
> > + drm_gpusvm_notifier_lock(gpusvm);
> > + range->flags.has_vram_pages = true;
> > + range->pages = pages;
> > + if (mmu_interval_read_retry(notifier,
> > hmm_range.notifier_seq)) {
> > + err = -EAGAIN;
> > + __drm_gpusvm_range_unmap_pages(gpusvm,
> > range);
> > + }
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > + } else {
> > + dma_addr_t *dma_addr = (dma_addr_t *)pfns;
> > +
> > + for_each_dma_page(i, j, npages, order) {
> > + if (WARN_ON_ONCE(i && order !=
> > +
> > hmm_pfn_to_map_order(pfns[i]))) {
> > + err = -EOPNOTSUPP;
> > + npages = i;
> > + goto err_unmap;
> > + }
> > + order = hmm_pfn_to_map_order(pfns[i]);
> > +
> > + pages[j] = hmm_pfn_to_page(pfns[i]);
> > + if
> > (WARN_ON_ONCE(is_zone_device_page(pages[j]))) {
> > + err = -EOPNOTSUPP;
> > + npages = i;
> > + goto err_unmap;
> > + }
> > +
> > + set_page_dirty_lock(pages[j]);
> > + mark_page_accessed(pages[j]);
> > +
> > + dma_addr[j] = dma_map_page(gpusvm->drm->dev,
> > + pages[j], 0,
> > + PAGE_SIZE <<
> > order,
> > +
> > DMA_BIDIRECTIONAL);
> > + if (dma_mapping_error(gpusvm->drm->dev,
> > dma_addr[j])) {
> > + err = -EFAULT;
> > + npages = i;
> > + goto err_unmap;
> > + }
> > + }
> > +
> > + /* Huge pages, reduce memory footprint */
> > + if (order) {
> > + dma_addr = kmalloc_array(j,
> > sizeof(*dma_addr),
> > + GFP_KERNEL);
> > + if (dma_addr) {
> > + for (i = 0; i < j; ++i)
> > + dma_addr[i] =
> > (dma_addr_t)pfns[i];
> > + kvfree(pfns);
> > + kfree_mapping = true;
> > + } else {
> > + dma_addr = (dma_addr_t *)pfns;
> > + }
> > + }
> > +
> > + /* Do not race with notifier unmapping pages */
> > + drm_gpusvm_notifier_lock(gpusvm);
> > + range->order = order;
> > + range->flags.kfree_mapping = kfree_mapping;
> > + range->flags.has_dma_mapping = true;
> > + range->dma_addr = dma_addr;
> > + range->vram_allocation = NULL;
> > + if (mmu_interval_read_retry(notifier,
> > hmm_range.notifier_seq)) {
> > + err = -EAGAIN;
> > + __drm_gpusvm_range_unmap_pages(gpusvm,
> > range);
> > + }
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > + }
> > +
> > + if (err == -EAGAIN)
> > + goto retry;
> > +set_seqno:
> > + range->notifier_seq = hmm_range.notifier_seq;
> > +
> > + return 0;
> > +
> > +err_unmap:
> > + for_each_dma_page(i, j, npages, order)
> > + dma_unmap_page(gpusvm->drm->dev,
> > + (dma_addr_t)pfns[j],
> > + PAGE_SIZE << order,
> > DMA_BIDIRECTIONAL);
> > +err_free:
> > + if (alloc_pfns)
> > + kvfree(pfns);
> > +err_out:
> > + return err;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_unmap_pages - Unmap pages associated with a GPU
> > SVM range
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + * @ctx: GPU SVM context
> > + *
> > + * This function unmaps pages associated with a GPU SVM range. If
> > @in_notifier
> > + * is set, it is assumed that gpusvm->notifier_lock is held in write
> > mode; if it
> > + * is clear, it acquires gpusvm->notifier_lock in read mode. Must be
> > called on
> > + * each GPU SVM range attached to notifier in gpusvm->ops-
> > >invalidate for IOMMU
> > + * security model.
> > + */
> > +void drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range,
> > + const struct drm_gpusvm_ctx *ctx)
> > +{
> > + if (ctx->in_notifier)
> > + lockdep_assert_held_write(&gpusvm->notifier_lock);
> > + else
> > + drm_gpusvm_notifier_lock(gpusvm);
> > +
> > + __drm_gpusvm_range_unmap_pages(gpusvm, range);
> > +
> > + if (!ctx->in_notifier)
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_migration_put_page - Put a migration page
> > + * @page: Pointer to the page to put
> > + *
> > + * This function unlocks and puts a page.
> > + */
> > +static void drm_gpusvm_migration_put_page(struct page *page)
> > +{
> > + unlock_page(page);
> > + put_page(page);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_migration_put_pages - Put migration pages
> > + * @npages: Number of pages
> > + * @migrate_pfn: Array of migrate page frame numbers
> > + *
> > + * This function puts an array of pages.
> > + */
> > +static void drm_gpusvm_migration_put_pages(unsigned long npages,
> > + unsigned long
> > *migrate_pfn)
> > +{
> > + unsigned long i;
> > +
> > + for (i = 0; i < npages; ++i) {
> > + if (!migrate_pfn[i])
> > + continue;
> > +
> > + drm_gpusvm_migration_put_page(migrate_pfn_to_page(mi
> > grate_pfn[i]));
> > + migrate_pfn[i] = 0;
> > + }
> > +}
> > +
> > +/**
> > + * drm_gpusvm_get_vram_page - Get a reference to a VRAM page
> > + * @page: Pointer to the page
> > + * @zdd: Pointer to the GPU SVM zone device data
> > + *
> > + * This function associates the given page with the specified GPU
> > SVM zone
> > + * device data and initializes it for zone device usage.
> > + */
> > +static void drm_gpusvm_get_vram_page(struct page *page,
> > + struct drm_gpusvm_zdd *zdd)
> > +{
> > + page->zone_device_data = drm_gpusvm_zdd_get(zdd);
> > + zone_device_page_init(page);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_migrate_map_pages() - Map migration pages for GPU SVM
> > migration
> > + * @dev: The device for which the pages are being mapped
> > + * @dma_addr: Array to store DMA addresses corresponding to mapped
> > pages
> > + * @migrate_pfn: Array of migrate page frame numbers to map
> > + * @npages: Number of pages to map
> > + * @dir: Direction of data transfer (e.g., DMA_BIDIRECTIONAL)
> > + *
> > + * This function maps pages of memory for migration usage in GPU
> > SVM. It
> > + * iterates over each page frame number provided in @migrate_pfn,
> > maps the
> > + * corresponding page, and stores the DMA address in the provided
> > @dma_addr
> > + * array.
> > + *
> > + * Return: 0 on success, -EFAULT if an error occurs during mapping.
> > + */
> > +static int drm_gpusvm_migrate_map_pages(struct device *dev,
> > + dma_addr_t *dma_addr,
> > + long unsigned int
> > *migrate_pfn,
> > + unsigned long npages,
> > + enum dma_data_direction dir)
> > +{
> > + unsigned long i;
> > +
> > + for (i = 0; i < npages; ++i) {
> > + struct page *page =
> > migrate_pfn_to_page(migrate_pfn[i]);
> > +
> > + if (!page)
> > + continue;
> > +
> > + if (WARN_ON_ONCE(is_zone_device_page(page)))
> > + return -EFAULT;
> > +
> > + dma_addr[i] = dma_map_page(dev, page, 0, PAGE_SIZE,
> > dir);
> > + if (dma_mapping_error(dev, dma_addr[i]))
> > + return -EFAULT;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_migrate_unmap_pages() - Unmap pages previously mapped
> > for GPU SVM migration
> > + * @dev: The device for which the pages were mapped
> > + * @dma_addr: Array of DMA addresses corresponding to mapped pages
> > + * @npages: Number of pages to unmap
> > + * @dir: Direction of data transfer (e.g., DMA_BIDIRECTIONAL)
> > + *
> > + * This function unmaps previously mapped pages of memory for GPU
> > Shared Virtual
> > + * Memory (SVM). It iterates over each DMA address provided in
> > @dma_addr, checks
> > + * if it's valid and not already unmapped, and unmaps the
> > corresponding page.
> > + */
> > +static void drm_gpusvm_migrate_unmap_pages(struct device *dev,
> > + dma_addr_t *dma_addr,
> > + unsigned long npages,
> > + enum dma_data_direction
> > dir)
> > +{
> > + unsigned long i;
> > +
> > + for (i = 0; i < npages; ++i) {
> > + if (!dma_addr[i] || dma_mapping_error(dev,
> > dma_addr[i]))
> > + continue;
> > +
> > + dma_unmap_page(dev, dma_addr[i], PAGE_SIZE, dir);
> > + }
> > +}
> > +
> > +/**
> > + * drm_gpusvm_migrate_to_vram - Migrate GPU SVM range to VRAM
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + * failure of this function.
> > + * @vram_allocation: Driver-private pointer to the VRAM allocation.
> > The caller
> > + * should hold a reference to the VRAM allocation,
> > which
> > + * should be dropped via ops->vram_allocation or
> > upon the
> > + * failure of this function.
> > + * @ctx: GPU SVM context
> > + *
> > + * This function migrates the specified GPU SVM range to VRAM. It
> > performs the
> > + * necessary setup and invokes the driver-specific operations for
> > migration to
> > + * VRAM. Upon successful return, @vram_allocation can safely
> > reference @range
> > + * until ops->vram_release is called which only upon successful
> > return.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure.
> > + */
> > +int drm_gpusvm_migrate_to_vram(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range,
> > + void *vram_allocation,
> > + const struct drm_gpusvm_ctx *ctx)
> > +{
> > + u64 start = range->va.start, end = range->va.end;
> > + struct migrate_vma migrate = {
> > + .start = start,
> > + .end = end,
> > + .pgmap_owner = gpusvm->device_private_page_owner,
> > + .flags = MIGRATE_VMA_SELECT_SYSTEM,
> > + };
> > + struct mm_struct *mm = gpusvm->mm;
> > + unsigned long i, npages = npages_in_range(start, end);
> > + struct vm_area_struct *vas;
> > + struct drm_gpusvm_zdd *zdd = NULL;
> > + struct page **pages;
> > + dma_addr_t *dma_addr;
> > + void *buf;
> > + int err;
> > +
> > + if (!range->flags.migrate_vram)
> > + return -EINVAL;
> > +
> > + if (!gpusvm->ops->populate_vram_pfn || !gpusvm->ops-
> > >copy_to_vram ||
> > + !gpusvm->ops->copy_to_sram)
> > + return -EOPNOTSUPP;
> > +
> > + if (!ctx->mmap_locked) {
> > + if (!mmget_not_zero(mm)) {
> > + err = -EFAULT;
> > + goto err_out;
> > + }
> > + mmap_write_lock(mm);
> > + }
> > +
> > + mmap_assert_locked(mm);
> > +
> > + vas = vma_lookup(mm, start);
> > + if (!vas) {
> > + err = -ENOENT;
> > + goto err_mmunlock;
> > + }
> > +
> > + if (end > vas->vm_end || start < vas->vm_start) {
> > + err = -EINVAL;
> > + goto err_mmunlock;
> > + }
> > +
> > + if (!vma_is_anonymous(vas)) {
> > + err = -EBUSY;
> > + goto err_mmunlock;
> > + }
> > +
> > + buf = kvcalloc(npages, 2 * sizeof(*migrate.src) +
> > sizeof(*dma_addr) +
> > + sizeof(*pages), GFP_KERNEL);
> > + if (!buf) {
> > + err = -ENOMEM;
> > + goto err_mmunlock;
> > + }
> > + dma_addr = buf + (2 * sizeof(*migrate.src) * npages);
> > + pages = buf + (2 * sizeof(*migrate.src) + sizeof(*dma_addr))
> > * npages;
> > +
> > + zdd = drm_gpusvm_zdd_alloc(range);
> > + if (!zdd) {
> > + err = -ENOMEM;
> > + goto err_free;
> > + }
> > +
> > + migrate.vma = vas;
> > + migrate.src = buf;
> > + migrate.dst = migrate.src + npages;
> > +
> > + err = migrate_vma_setup(&migrate);
> > + if (err)
> > + goto err_free;
> > +
> > + /*
> > + * FIXME: Below cases, !migrate.cpages and migrate.cpages !=
> > npages, not
> > + * always an error. Need to revisit possible cases and how
> > to handle. We
> > + * could prefault on migrate.cpages != npages via
> > hmm_range_fault.
> > + */
> > +
> > + if (!migrate.cpages) {
> > + err = -EFAULT;
> > + goto err_free;
> > + }
> > +
> > + if (migrate.cpages != npages) {
> > + err = -EBUSY;
> > + goto err_finalize;
> > + }
> > +
> > + err = gpusvm->ops->populate_vram_pfn(gpusvm,
> > vram_allocation, npages,
> > + migrate.dst);
> > + if (err)
> > + goto err_finalize;
> > +
> > + err = drm_gpusvm_migrate_map_pages(gpusvm->drm->dev,
> > dma_addr,
> > + migrate.src, npages,
> > DMA_TO_DEVICE);
> > + if (err)
> > + goto err_finalize;
> > +
> > + for (i = 0; i < npages; ++i) {
> > + struct page *page = pfn_to_page(migrate.dst[i]);
> > +
> > + pages[i] = page;
> > + migrate.dst[i] = migrate_pfn(migrate.dst[i]);
> > + drm_gpusvm_get_vram_page(page, zdd);
> > + }
> > +
> > + err = gpusvm->ops->copy_to_vram(gpusvm, pages, dma_addr,
> > npages);
> > + if (err)
> > + goto err_finalize;
> > +
> > + /* Upon success bind vram allocation to range and zdd */
> > + range->vram_allocation = vram_allocation;
> > + WRITE_ONCE(zdd->vram_allocation, vram_allocation); /*
> > Owns ref */
> > +
> > +err_finalize:
> > + if (err)
> > + drm_gpusvm_migration_put_pages(npages, migrate.dst);
> > + migrate_vma_pages(&migrate);
> > + migrate_vma_finalize(&migrate);
> > + drm_gpusvm_migrate_unmap_pages(gpusvm->drm->dev, dma_addr,
> > npages,
> > + DMA_TO_DEVICE);
> > +err_free:
> > + if (zdd)
> > + drm_gpusvm_zdd_put(zdd);
> > + kvfree(buf);
> > +err_mmunlock:
> > + if (!ctx->mmap_locked) {
> > + mmap_write_unlock(mm);
> > + mmput(mm);
> > + }
> > +err_out:
> > + return err;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_migrate_populate_sram_pfn - Populate SRAM PFNs for a
> > VM area
> > + * @vas: Pointer to the VM area structure, can be NULL
> > + * @npages: Number of pages to populate
> > + * @src_mpfn: Source array of migrate PFNs
> > + * @mpfn: Array of migrate PFNs to populate
> > + * @addr: Start address for PFN allocation
> > + *
> > + * This function populates the SRAM migrate page frame numbers
> > (PFNs) for the
> > + * specified VM area structure. It allocates and locks pages in the
> > VM area for
> > + * SRAM usage. If vas is non-NULL use alloc_page_vma for allocation,
> > if NULL use
> > + * alloc_page for allocation.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure.
> > + */
> > +static int drm_gpusvm_migrate_populate_sram_pfn(struct
> > vm_area_struct *vas,
> > + unsigned long
> > npages,
> > + unsigned long
> > *src_mpfn,
> > + unsigned long *mpfn,
> > u64 addr)
> > +{
> > + unsigned long i;
> > +
> > + for (i = 0; i < npages; ++i, addr += PAGE_SIZE) {
> > + struct page *page;
> > +
> > + if (!(src_mpfn[i] & MIGRATE_PFN_MIGRATE))
> > + continue;
> > +
> > + if (vas)
> > + page = alloc_page_vma(GFP_HIGHUSER, vas,
> > addr);
> > + else
> > + page = alloc_page(GFP_HIGHUSER);
> > +
> > + if (!page)
> > + return -ENOMEM;
> > +
> > + lock_page(page);
> > + mpfn[i] = migrate_pfn(page_to_pfn(page));
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_evict_to_sram - Evict GPU SVM range to SRAM
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + *
> > + * Similar to __drm_gpusvm_migrate_to_sram but does not require mmap
> > lock and
> > + * migration done via migrate_device_* functions. Fallback path as
> > it is
> > + * preferred to issue migrations with mmap lock.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure.
> > + */
> > +static int drm_gpusvm_evict_to_sram(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range)
> > +{
> > + unsigned long npages;
> > + struct page **pages;
> > + unsigned long *src, *dst;
> > + dma_addr_t *dma_addr;
> > + void *buf;
> > + int i, err = 0;
> > +
> > + npages = npages_in_range(range->va.start, range->va.end);
> > +
> > + buf = kvcalloc(npages, 2 * sizeof(*src) + sizeof(*dma_addr)
> > +
> > + sizeof(*pages), GFP_KERNEL);
> > + if (!buf) {
> > + err = -ENOMEM;
> > + goto err_out;
> > + }
> > + src = buf;
> > + dst = buf + (sizeof(*src) * npages);
> > + dma_addr = buf + (2 * sizeof(*src) * npages);
> > + pages = buf + (2 * sizeof(*src) + sizeof(*dma_addr)) *
> > npages;
> > +
> > + err = gpusvm->ops->populate_vram_pfn(gpusvm, range-
> > >vram_allocation,
> > + npages, src);
> > + if (err)
> > + goto err_free;
> > +
> > + err = migrate_device_vma_range(gpusvm->mm,
> > + gpusvm-
> > >device_private_page_owner, src,
> > + npages, range->va.start);
> > + if (err)
> > + goto err_free;
> > +
> > + err = drm_gpusvm_migrate_populate_sram_pfn(NULL, npages,
> > src, dst, 0);
> > + if (err)
> > + goto err_finalize;
> > +
> > + err = drm_gpusvm_migrate_map_pages(gpusvm->drm->dev,
> > dma_addr,
> > + dst, npages,
> > DMA_BIDIRECTIONAL);
> > + if (err)
> > + goto err_finalize;
> > +
> > + for (i = 0; i < npages; ++i)
> > + pages[i] = migrate_pfn_to_page(src[i]);
> > +
> > + err = gpusvm->ops->copy_to_sram(gpusvm, pages, dma_addr,
> > npages);
> > + if (err)
> > + goto err_finalize;
> > +
> > +err_finalize:
> > + if (err)
> > + drm_gpusvm_migration_put_pages(npages, dst);
> > + migrate_device_pages(src, dst, npages);
> > + migrate_device_finalize(src, dst, npages);
> > + drm_gpusvm_migrate_unmap_pages(gpusvm->drm->dev, dma_addr,
> > npages,
> > + DMA_BIDIRECTIONAL);
> > +err_free:
> > + kvfree(buf);
> > +err_out:
> > +
> > + return err;
> > +}
> > +
> > +/**
> > + * __drm_gpusvm_migrate_to_sram - Migrate GPU SVM range to SRAM
> > (internal)
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @vas: Pointer to the VM area structure
> > + * @page: Pointer to the page for fault handling (can be NULL)
> > + * @start: Start address of the migration range
> > + * @end: End address of the migration range
> > + *
> > + * This internal function performs the migration of the specified
> > GPU SVM range
> > + * to SRAM. It sets up the migration, populates + dma maps SRAM
> > PFNs, and
> > + * invokes the driver-specific operations for migration to SRAM.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure.
> > + */
> > +static int __drm_gpusvm_migrate_to_sram(struct drm_gpusvm *gpusvm,
> > + struct vm_area_struct *vas,
> > + struct page *page,
> > + u64 start, u64 end)
> > +{
> > + struct migrate_vma migrate = {
> > + .vma = vas,
> > + .pgmap_owner = gpusvm->device_private_page_owner,
> > + .flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE,
> > + .fault_page = page,
> > + };
> > + unsigned long npages;
> > + struct page **pages;
> > + dma_addr_t *dma_addr;
> > + void *buf;
> > + int i, err = 0;
> > +
> > + mmap_assert_locked(gpusvm->mm);
> > +
> > + /* Corner where VMA area struct has been partially unmapped
> > */
> > + if (start < vas->vm_start)
> > + start = vas->vm_start;
> > + if (end > vas->vm_end)
> > + end = vas->vm_end;
> > +
> > + migrate.start = start;
> > + migrate.end = end;
> > + npages = npages_in_range(start, end);
> > +
> > + buf = kvcalloc(npages, 2 * sizeof(*migrate.src) +
> > sizeof(*dma_addr) +
> > + sizeof(*pages), GFP_KERNEL);
> > + if (!buf) {
> > + err = -ENOMEM;
> > + goto err_out;
> > + }
> > + dma_addr = buf + (2 * sizeof(*migrate.src) * npages);
> > + pages = buf + (2 * sizeof(*migrate.src) + sizeof(*dma_addr))
> > * npages;
> > +
> > + migrate.vma = vas;
> > + migrate.src = buf;
> > + migrate.dst = migrate.src + npages;
> > +
> > + err = migrate_vma_setup(&migrate);
> > + if (err)
> > + goto err_free;
> > +
> > + /* Raced with another CPU fault, nothing to do */
> > + if (!migrate.cpages)
> > + goto err_free;
> > +
> > + err = drm_gpusvm_migrate_populate_sram_pfn(vas, npages,
> > + migrate.src,
> > migrate.dst,
> > + start);
> > + if (err)
> > + goto err_finalize;
> > +
> > + err = drm_gpusvm_migrate_map_pages(gpusvm->drm->dev,
> > dma_addr,
> > + migrate.dst, npages,
> > + DMA_BIDIRECTIONAL);
> > + if (err)
> > + goto err_finalize;
> > +
> > + for (i = 0; i < npages; ++i)
> > + pages[i] = migrate_pfn_to_page(migrate.src[i]);
>
> See comments below which pages we actually want to migrate.
>
>
> > +
> > + err = gpusvm->ops->copy_to_sram(gpusvm, pages, dma_addr,
> > npages);
> > + if (err)
> > + goto err_finalize;
> > +
> > +err_finalize:
> > + if (err)
> > + drm_gpusvm_migration_put_pages(npages, migrate.dst);
> > + migrate_vma_pages(&migrate);
> > + migrate_vma_finalize(&migrate);
> > + drm_gpusvm_migrate_unmap_pages(gpusvm->drm->dev, dma_addr,
> > npages,
> > + DMA_BIDIRECTIONAL);
> > +err_free:
> > + kvfree(buf);
> > +err_out:
> > + mmap_assert_locked(gpusvm->mm);
> > +
> > + return err;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_migrate_to_sram - Migrate (evict) GPU SVM range to
> > SRAM
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + * @ctx: GPU SVM context
> > + *
> > + * This function initiates the migration of the specified GPU SVM
> > range to
> > + * SRAM. It performs necessary checks and invokes the internal
> > migration
> > + * function for actual migration.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure.
> > + */
> > +int drm_gpusvm_migrate_to_sram(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range,
> > + const struct drm_gpusvm_ctx *ctx)
> > +{
> > + u64 start = range->va.start, end = range->va.end;
> > + struct mm_struct *mm = gpusvm->mm;
> > + struct vm_area_struct *vas;
> > + int err;
> > + bool retry = false;
> > +
> > + if (!ctx->mmap_locked) {
> > + if (!mmget_not_zero(mm)) {
> > + err = -EFAULT;
> > + goto err_out;
> > + }
> > + if (ctx->trylock_mmap) {
> > + if (!mmap_read_trylock(mm)) {
> > + err =
> > drm_gpusvm_evict_to_sram(gpusvm, range);
> > + goto err_mmput;
> > + }
> > + } else {
> > + mmap_read_lock(mm);
> > + }
> > + }
> > +
> > + mmap_assert_locked(mm);
> > +
> > + /*
> > + * Loop required to find all VMA area structs for the corner
> > case when
> > + * VRAM backing has been partially unmapped from MM's
> > address space.
> > + */
> > +again:
> > + vas = find_vma(mm, start);
> > + if (!vas) {
> > + if (!retry)
> > + err = -ENOENT;
> > + goto err_mmunlock;
> > + }
> > +
> > + if (end <= vas->vm_start || start >= vas->vm_end) {
> > + if (!retry)
> > + err = -EINVAL;
> > + goto err_mmunlock;
> > + }
> > +
> > + err = __drm_gpusvm_migrate_to_sram(gpusvm, vas, NULL, start,
> > end);
>
> This function is typically called from the vm side to get a clean mm as
> a last resort after get_pages() fail. As such should we have it evict
> *everything*, even foreign device memory, and mismatching local device
> pages. If so, we could use hmm_range_fault() with a NULL page owner +
> faulting to do that.
>
I've actually tried that and it seemed to mostly work well and actually
would be my preference as this avoids a VMA lookup in GPU SVM.
I think it is problem though if some of the pages are partially unmapped
though as hmm_range_fault will abort if fault cannot be resolved. Maybe
I'm mistaken on this. I won't get this in rev2 but will put this on my
list to continue to play around with.
> > + if (err)
> > + goto err_mmunlock;
> > +
> > + if (vas->vm_end < end) {
> > + retry = true;
> > + start = vas->vm_end;
> > + goto again;
> > + }
> > +
> > + if (!ctx->mmap_locked) {
> > + mmap_read_unlock(mm);
> > + /*
> > + * Using mmput_async as this function can be called
> > while
> > + * holding a dma-resv lock, and a final put can grab
> > the mmap
> > + * lock, causing a lock inversion.
> > + */
> > + mmput_async(mm);
> > + }
> > +
> > + return 0;
> > +
> > +err_mmunlock:
> > + if (!ctx->mmap_locked)
> > + mmap_read_unlock(mm);
> > +err_mmput:
> > + if (!ctx->mmap_locked)
> > + mmput_async(mm);
> > +err_out:
> > + return err;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_page_free - Put GPU SVM zone device data associated
> > with a page
> > + * @page: Pointer to the page
> > + *
> > + * This function is a callback used to put the GPU SVM zone device
> > data
> > + * associated with a page when it is being released.
> > + */
> > +static void drm_gpusvm_page_free(struct page *page)
> > +{
> > + drm_gpusvm_zdd_put(page->zone_device_data);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_migrate_to_ram - Migrate GPU SVM range to RAM (page
> > fault handler)
> > + * @vmf: Pointer to the fault information structure
> > + *
> > + * This function is a page fault handler used to migrate a GPU SVM
> > range to RAM.
> > + * It retrieves the GPU SVM range information from the faulting page
> > and invokes
> > + * the internal migration function to migrate the range back to RAM.
> > + *
> > + * Returns:
> > + * VM_FAULT_SIGBUS on failure, 0 on success.
> > + */
> > +static vm_fault_t drm_gpusvm_migrate_to_ram(struct vm_fault *vmf)
> > +{
> > + struct drm_gpusvm_zdd *zdd = vmf->page->zone_device_data;
> > + int err;
> > +
> > + err = __drm_gpusvm_migrate_to_sram(zdd->range->gpusvm,
> > + vmf->vma, vmf->page,
> > + zdd->range->va.start,
> > + zdd->range->va.end);
>
> When called from here, since this is a pagemap op, we should ensure we
> only migrate our own pagemap to RAM?
>
I think you resolve this with the following the patch [1], right? I
think I agree.
Matt
[1] https://patchwork.freedesktop.org/series/139994/
> /Thanks,
> Thomas
>
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