[RFC 02/10] drm/i915/vm_bind: Bind and unbind mappings
Thomas Hellström
thomas.hellstrom at linux.intel.com
Wed Jul 6 16:21:03 UTC 2022
On Fri, 2022-07-01 at 15:50 -0700, Niranjana Vishwanathapura wrote:
> Bind and unbind the mappings upon VM_BIND and VM_UNBIND calls.
>
> Signed-off-by: Niranjana Vishwanathapura
> <niranjana.vishwanathapura at intel.com>
> Signed-off-by: Prathap Kumar Valsan <prathap.kumar.valsan at intel.com>
> ---
> drivers/gpu/drm/i915/Makefile | 1 +
> drivers/gpu/drm/i915/gem/i915_gem_create.c | 10 +-
> drivers/gpu/drm/i915/gem/i915_gem_object.h | 2 +
> drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h | 38 +++
> .../drm/i915/gem/i915_gem_vm_bind_object.c | 233
> ++++++++++++++++++
> drivers/gpu/drm/i915/gt/intel_gtt.c | 7 +
> drivers/gpu/drm/i915/gt/intel_gtt.h | 9 +
> drivers/gpu/drm/i915/i915_driver.c | 11 +-
> drivers/gpu/drm/i915/i915_vma.c | 7 +-
> drivers/gpu/drm/i915/i915_vma.h | 2 -
> drivers/gpu/drm/i915/i915_vma_types.h | 8 +
> 11 files changed, 318 insertions(+), 10 deletions(-)
> create mode 100644 drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
> create mode 100644
> drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
>
> diff --git a/drivers/gpu/drm/i915/Makefile
> b/drivers/gpu/drm/i915/Makefile
> index 522ef9b4aff3..4e1627e96c6e 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -165,6 +165,7 @@ gem-y += \
> gem/i915_gem_ttm_move.o \
> gem/i915_gem_ttm_pm.o \
> gem/i915_gem_userptr.o \
> + gem/i915_gem_vm_bind_object.o \
> gem/i915_gem_wait.o \
> gem/i915_gemfs.o
> i915-y += \
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_create.c
> b/drivers/gpu/drm/i915/gem/i915_gem_create.c
> index 33673fe7ee0a..927a87e5ec59 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_create.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_create.c
> @@ -15,10 +15,10 @@
> #include "i915_trace.h"
> #include "i915_user_extensions.h"
>
> -static u32 object_max_page_size(struct intel_memory_region
> **placements,
> - unsigned int n_placements)
> +u32 i915_gem_object_max_page_size(struct intel_memory_region
> **placements,
Kerneldoc.
> + unsigned int n_placements)
> {
> - u32 max_page_size = 0;
> + u32 max_page_size = I915_GTT_PAGE_SIZE_4K;
> int i;
>
> for (i = 0; i < n_placements; i++) {
> @@ -28,7 +28,6 @@ static u32 object_max_page_size(struct
> intel_memory_region **placements,
> max_page_size = max_t(u32, max_page_size, mr-
> >min_page_size);
> }
>
> - GEM_BUG_ON(!max_page_size);
> return max_page_size;
> }
Should this change be separated out? It's not immediately clear to a
reviewer why it is included.
>
> @@ -99,7 +98,8 @@ __i915_gem_object_create_user_ext(struct
> drm_i915_private *i915, u64 size,
>
> i915_gem_flush_free_objects(i915);
>
> - size = round_up(size, object_max_page_size(placements,
> n_placements));
> + size = round_up(size,
> i915_gem_object_max_page_size(placements,
> +
> n_placements));
> if (size == 0)
> return ERR_PTR(-EINVAL);
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> index 6f0a3ce35567..650de2224843 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> @@ -47,6 +47,8 @@ static inline bool i915_gem_object_size_2big(u64
> size)
> }
>
> void i915_gem_init__objects(struct drm_i915_private *i915);
> +u32 i915_gem_object_max_page_size(struct intel_memory_region
> **placements,
> + unsigned int n_placements);
>
> void i915_objects_module_exit(void);
> int i915_objects_module_init(void);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
> b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
> new file mode 100644
> index 000000000000..642cdb559f17
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright © 2022 Intel Corporation
> + */
> +
> +#ifndef __I915_GEM_VM_BIND_H
> +#define __I915_GEM_VM_BIND_H
> +
> +#include "i915_drv.h"
> +
> +#define assert_vm_bind_held(vm) lockdep_assert_held(&(vm)-
> >vm_bind_lock)
> +
> +static inline void i915_gem_vm_bind_lock(struct i915_address_space
> *vm)
> +{
> + mutex_lock(&vm->vm_bind_lock);
> +}
> +
> +static inline int
> +i915_gem_vm_bind_lock_interruptible(struct i915_address_space *vm)
> +{
> + return mutex_lock_interruptible(&vm->vm_bind_lock);
> +}
> +
> +static inline void i915_gem_vm_bind_unlock(struct i915_address_space
> *vm)
> +{
> + mutex_unlock(&vm->vm_bind_lock);
> +}
> +
Kerneldoc for the inlines.
> +struct i915_vma *
> +i915_gem_vm_bind_lookup_vma(struct i915_address_space *vm, u64 va);
> +void i915_gem_vm_bind_remove(struct i915_vma *vma, bool
> release_obj);
> +int i915_gem_vm_bind_obj(struct i915_address_space *vm,
> + struct drm_i915_gem_vm_bind *va,
> + struct drm_file *file);
> +int i915_gem_vm_unbind_obj(struct i915_address_space *vm,
> + struct drm_i915_gem_vm_unbind *va);
> +
> +#endif /* __I915_GEM_VM_BIND_H */
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
> b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
> new file mode 100644
> index 000000000000..43ceb4dcca6c
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_vm_bind_object.c
> @@ -0,0 +1,233 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2022 Intel Corporation
> + */
> +
> +#include <linux/interval_tree_generic.h>
> +
> +#include "gem/i915_gem_vm_bind.h"
> +#include "gt/gen8_engine_cs.h"
> +
> +#include "i915_drv.h"
> +#include "i915_gem_gtt.h"
> +
> +#define START(node) ((node)->start)
> +#define LAST(node) ((node)->last)
> +
> +INTERVAL_TREE_DEFINE(struct i915_vma, rb, u64, __subtree_last,
> + START, LAST, static inline, i915_vm_bind_it)
> +
> +#undef START
> +#undef LAST
> +
> +/**
> + * DOC: VM_BIND/UNBIND ioctls
> + *
> + * DRM_I915_GEM_VM_BIND/UNBIND ioctls allows UMD to bind/unbind GEM
> buffer
> + * objects (BOs) or sections of a BOs at specified GPU virtual
> addresses on a
> + * specified address space (VM). Multiple mappings can map to the
> same physical
> + * pages of an object (aliasing). These mappings (also referred to
> as persistent
> + * mappings) will be persistent across multiple GPU submissions
> (execbuf calls)
> + * issued by the UMD, without user having to provide a list of all
> required
> + * mappings during each submission (as required by older execbuf
> mode).
> + *
> + * The VM_BIND/UNBIND calls allow UMDs to request a timeline out
> fence for
> + * signaling the completion of bind/unbind operation.
> + *
> + * VM_BIND feature is advertised to user via
> I915_PARAM_VM_BIND_VERSION.
> + * User has to opt-in for VM_BIND mode of binding for an address
> space (VM)
> + * during VM creation time via I915_VM_CREATE_FLAGS_USE_VM_BIND
> extension.
> + *
> + * VM_BIND/UNBIND ioctl calls executed on different CPU threads
> concurrently
> + * are not ordered. Furthermore, parts of the VM_BIND/UNBIND
> operations can be
> + * done asynchronously, when valid out fence is specified.
> + *
> + * VM_BIND locking order is as below.
> + *
> + * 1) Lock-A: A vm_bind mutex will protect vm_bind lists. This lock
> is taken in
> + * vm_bind/vm_unbind ioctl calls, in the execbuf path and while
> releasing the
> + * mapping.
> + *
> + * In future, when GPU page faults are supported, we can
> potentially use a
> + * rwsem instead, so that multiple page fault handlers can take
> the read
> + * side lock to lookup the mapping and hence can run in parallel.
> + * The older execbuf mode of binding do not need this lock.
> + *
> + * 2) Lock-B: The object's dma-resv lock will protect i915_vma state
> and needs
> + * to be held while binding/unbinding a vma in the async worker
> and while
> + * updating dma-resv fence list of an object. Note that private
> BOs of a VM
> + * will all share a dma-resv object.
> + *
> + * The future system allocator support will use the HMM
> prescribed locking
> + * instead.
I don't think the last sentence is relevant for this series. Also, are
there any other mentions for Locks A, B and C? If not, can we ditch
that naming?
> + *
> + * 3) Lock-C: Spinlock/s to protect some of the VM's lists like the
> list of
> + * invalidated vmas (due to eviction and userptr invalidation)
> etc.
> + */
> +
> +struct i915_vma *
> +i915_gem_vm_bind_lookup_vma(struct i915_address_space *vm, u64 va)
Kerneldoc for the extern functions.
> +{
> + struct i915_vma *vma, *temp;
> +
> + assert_vm_bind_held(vm);
> +
> + vma = i915_vm_bind_it_iter_first(&vm->va, va, va);
> + /* Working around compiler error, remove later */
Is this still relevant? What compiler error is seen here?
> + if (vma)
> + temp = i915_vm_bind_it_iter_next(vma, va + vma->size,
> -1);
> + return vma;
> +}
> +
> +void i915_gem_vm_bind_remove(struct i915_vma *vma, bool release_obj)
> +{
> + assert_vm_bind_held(vma->vm);
> +
> + if (!list_empty(&vma->vm_bind_link)) {
> + list_del_init(&vma->vm_bind_link);
> + i915_vm_bind_it_remove(vma, &vma->vm->va);
> +
> + /* Release object */
> + if (release_obj)
> + i915_vma_put(vma);
i915_vma_put() here is confusing. Can we use i915_gem_object_put() to
further make it clear that the persistent vmas actually take a
reference on the object?
> + }
> +}
> +
> +int i915_gem_vm_unbind_obj(struct i915_address_space *vm,
> + struct drm_i915_gem_vm_unbind *va)
> +{
> + struct drm_i915_gem_object *obj;
> + struct i915_vma *vma;
> + int ret;
> +
> + va->start = gen8_noncanonical_addr(va->start);
> + ret = i915_gem_vm_bind_lock_interruptible(vm);
> + if (ret)
> + return ret;
> +
> + vma = i915_gem_vm_bind_lookup_vma(vm, va->start);
> + if (!vma) {
> + ret = -ENOENT;
> + goto out_unlock;
> + }
> +
> + if (vma->size != va->length)
> + ret = -EINVAL;
> + else
> + i915_gem_vm_bind_remove(vma, false);
> +
> +out_unlock:
> + i915_gem_vm_bind_unlock(vm);
> + if (ret || !vma)
> + return ret;
> +
> + /* Destroy vma and then release object */
> + obj = vma->obj;
> + ret = i915_gem_object_lock(obj, NULL);
> + if (ret)
> + return ret;
This call never returns an error and we could GEM_WARN_ON(...), or
(void) to annotate that the return value is wilfully ignored.
> +
> + i915_vma_destroy(vma);
> + i915_gem_object_unlock(obj);
> + i915_gem_object_put(obj);
> +
> + return 0;
> +}
> +
> +static struct i915_vma *vm_bind_get_vma(struct i915_address_space
> *vm,
> + struct drm_i915_gem_object
> *obj,
> + struct drm_i915_gem_vm_bind
> *va)
> +{
> + struct i915_ggtt_view view;
> + struct i915_vma *vma;
> +
> + va->start = gen8_noncanonical_addr(va->start);
> + vma = i915_gem_vm_bind_lookup_vma(vm, va->start);
> + if (vma)
> + return ERR_PTR(-EEXIST);
> +
> + view.type = I915_GGTT_VIEW_PARTIAL;
> + view.partial.offset = va->offset >> PAGE_SHIFT;
> + view.partial.size = va->length >> PAGE_SHIFT;
IIRC, this vma view is not handled correctly in the vma code, that only
understands views for ggtt bindings.
> + vma = i915_vma_instance(obj, vm, &view);
> + if (IS_ERR(vma))
> + return vma;
> +
> + vma->start = va->start;
> + vma->last = va->start + va->length - 1;
> +
> + return vma;
> +}
> +
> +int i915_gem_vm_bind_obj(struct i915_address_space *vm,
> + struct drm_i915_gem_vm_bind *va,
> + struct drm_file *file)
> +{
> + struct drm_i915_gem_object *obj;
> + struct i915_vma *vma = NULL;
> + struct i915_gem_ww_ctx ww;
> + u64 pin_flags;
> + int ret = 0;
> +
> + if (!vm->vm_bind_mode)
> + return -EOPNOTSUPP;
> +
> + obj = i915_gem_object_lookup(file, va->handle);
> + if (!obj)
> + return -ENOENT;
> +
> + if (!va->length ||
> + !IS_ALIGNED(va->offset | va->length,
> + i915_gem_object_max_page_size(obj-
> >mm.placements,
> + obj-
> >mm.n_placements)) ||
> + range_overflows_t(u64, va->offset, va->length, obj-
> >base.size)) {
> + ret = -EINVAL;
> + goto put_obj;
> + }
> +
> + ret = i915_gem_vm_bind_lock_interruptible(vm);
> + if (ret)
> + goto put_obj;
> +
> + vma = vm_bind_get_vma(vm, obj, va);
> + if (IS_ERR(vma)) {
> + ret = PTR_ERR(vma);
> + goto unlock_vm;
> + }
> +
> + i915_gem_ww_ctx_init(&ww, true);
> + pin_flags = va->start | PIN_OFFSET_FIXED | PIN_USER;
> +retry:
> + ret = i915_gem_object_lock(vma->obj, &ww);
> + if (ret)
> + goto out_ww;
> +
> + ret = i915_vma_pin_ww(vma, &ww, 0, 0, pin_flags);
> + if (ret)
> + goto out_ww;
> +
> + /* Make it evictable */
> + __i915_vma_unpin(vma);
A considerable effort has been put into avoiding short term vma pins in
i915. We should add an interface like i915_vma_bind_ww() that avoids
the pin altoghether.
> +
> + list_add_tail(&vma->vm_bind_link, &vm->vm_bound_list);
> + i915_vm_bind_it_insert(vma, &vm->va);
> +
> + /* Hold object reference until vm_unbind */
> + i915_gem_object_get(vma->obj);
> +out_ww:
> + if (ret == -EDEADLK) {
> + ret = i915_gem_ww_ctx_backoff(&ww);
> + if (!ret)
> + goto retry;
> + }
> +
> + if (ret)
> + i915_vma_destroy(vma);
> +
> + i915_gem_ww_ctx_fini(&ww);
Could use for_i915_gem_ww()?
> +unlock_vm:
> + i915_gem_vm_bind_unlock(vm);
> +put_obj:
> + i915_gem_object_put(obj);
> + return ret;
> +}
> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c
> b/drivers/gpu/drm/i915/gt/intel_gtt.c
> index b67831833c9a..135dc4a76724 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gtt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
> @@ -176,6 +176,8 @@ int i915_vm_lock_objects(struct
> i915_address_space *vm,
> void i915_address_space_fini(struct i915_address_space *vm)
> {
> drm_mm_takedown(&vm->mm);
> + GEM_BUG_ON(!RB_EMPTY_ROOT(&vm->va.rb_root));
> + mutex_destroy(&vm->vm_bind_lock);
> }
>
> /**
> @@ -282,6 +284,11 @@ void i915_address_space_init(struct
> i915_address_space *vm, int subclass)
>
> INIT_LIST_HEAD(&vm->bound_list);
> INIT_LIST_HEAD(&vm->unbound_list);
> +
> + vm->va = RB_ROOT_CACHED;
> + INIT_LIST_HEAD(&vm->vm_bind_list);
> + INIT_LIST_HEAD(&vm->vm_bound_list);
> + mutex_init(&vm->vm_bind_lock);
> }
>
> void *__px_vaddr(struct drm_i915_gem_object *p)
> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h
> b/drivers/gpu/drm/i915/gt/intel_gtt.h
> index c812aa9708ae..d4a6ce65251d 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gtt.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
> @@ -259,6 +259,15 @@ struct i915_address_space {
> */
> struct list_head unbound_list;
>
> + /**
> + * List of VM_BIND objects.
> + */
Proper kerneldoc + intel locking guidelines comments, please.
> + struct mutex vm_bind_lock; /* Protects vm_bind lists */
> + struct list_head vm_bind_list;
> + struct list_head vm_bound_list;
> + /* va tree of persistent vmas */
> + struct rb_root_cached va;
> +
> /* Global GTT */
> bool is_ggtt:1;
>
> diff --git a/drivers/gpu/drm/i915/i915_driver.c
> b/drivers/gpu/drm/i915/i915_driver.c
> index ccf990dfd99b..776ab7844f60 100644
> --- a/drivers/gpu/drm/i915/i915_driver.c
> +++ b/drivers/gpu/drm/i915/i915_driver.c
> @@ -68,6 +68,7 @@
> #include "gem/i915_gem_ioctls.h"
> #include "gem/i915_gem_mman.h"
> #include "gem/i915_gem_pm.h"
> +#include "gem/i915_gem_vm_bind.h"
> #include "gt/intel_gt.h"
> #include "gt/intel_gt_pm.h"
> #include "gt/intel_rc6.h"
> @@ -1783,13 +1784,16 @@ static int i915_gem_vm_bind_ioctl(struct
> drm_device *dev, void *data,
> {
> struct drm_i915_gem_vm_bind *args = data;
> struct i915_address_space *vm;
> + int ret;
>
> vm = i915_gem_vm_lookup(file->driver_priv, args->vm_id);
> if (unlikely(!vm))
> return -ENOENT;
>
> + ret = i915_gem_vm_bind_obj(vm, args, file);
> +
> i915_vm_put(vm);
> - return -EINVAL;
> + return ret;
> }
>
> static int i915_gem_vm_unbind_ioctl(struct drm_device *dev, void
> *data,
> @@ -1797,13 +1801,16 @@ static int i915_gem_vm_unbind_ioctl(struct
> drm_device *dev, void *data,
> {
> struct drm_i915_gem_vm_unbind *args = data;
> struct i915_address_space *vm;
> + int ret;
>
> vm = i915_gem_vm_lookup(file->driver_priv, args->vm_id);
> if (unlikely(!vm))
> return -ENOENT;
>
> + ret = i915_gem_vm_unbind_obj(vm, args);
> +
> i915_vm_put(vm);
> - return -EINVAL;
> + return ret;
> }
>
> static const struct drm_ioctl_desc i915_ioctls[] = {
> diff --git a/drivers/gpu/drm/i915/i915_vma.c
> b/drivers/gpu/drm/i915/i915_vma.c
> index 43339ecabd73..d324e29cef0a 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -29,6 +29,7 @@
> #include "display/intel_frontbuffer.h"
> #include "gem/i915_gem_lmem.h"
> #include "gem/i915_gem_tiling.h"
> +#include "gem/i915_gem_vm_bind.h"
> #include "gt/intel_engine.h"
> #include "gt/intel_engine_heartbeat.h"
> #include "gt/intel_gt.h"
> @@ -234,6 +235,7 @@ vma_create(struct drm_i915_gem_object *obj,
> spin_unlock(&obj->vma.lock);
> mutex_unlock(&vm->mutex);
>
> + INIT_LIST_HEAD(&vma->vm_bind_link);
> return vma;
>
> err_unlock:
> @@ -290,7 +292,6 @@ i915_vma_instance(struct drm_i915_gem_object
> *obj,
> {
> struct i915_vma *vma;
>
> - GEM_BUG_ON(view && !i915_is_ggtt_or_dpt(vm));
> GEM_BUG_ON(!kref_read(&vm->ref));
>
> spin_lock(&obj->vma.lock);
> @@ -1660,6 +1661,10 @@ static void release_references(struct i915_vma
> *vma, bool vm_ddestroy)
>
> spin_unlock(&obj->vma.lock);
>
> + i915_gem_vm_bind_lock(vma->vm);
> + i915_gem_vm_bind_remove(vma, true);
> + i915_gem_vm_bind_unlock(vma->vm);
> +
The vm might be destroyed at this point already.
From what I understand we can destroy the vma from three call sites:
1) VM_UNBIND -> The vma has already been removed from the vm_bind
address space,
2) object destruction -> since the vma has an object reference while in
the vm_bind address space, it must also have been removed from the
address space if called from object destruction.
3) vm destruction. Suggestion is to call VM_UNBIND from under the
vm_bind lock early in vm destruction.
Then the above added code can be removed and replaced with an assert
that the vm_bind address space RB_NODE is indeed empty.
> spin_lock_irq(>->closed_lock);
> __i915_vma_remove_closed(vma);
> spin_unlock_irq(>->closed_lock);
> diff --git a/drivers/gpu/drm/i915/i915_vma.h
> b/drivers/gpu/drm/i915/i915_vma.h
> index 88ca0bd9c900..dcb49f79ff7e 100644
> --- a/drivers/gpu/drm/i915/i915_vma.h
> +++ b/drivers/gpu/drm/i915/i915_vma.h
> @@ -164,8 +164,6 @@ i915_vma_compare(struct i915_vma *vma,
> {
> ptrdiff_t cmp;
>
> - GEM_BUG_ON(view && !i915_is_ggtt_or_dpt(vm));
> -
> cmp = ptrdiff(vma->vm, vm);
> if (cmp)
> return cmp;
> diff --git a/drivers/gpu/drm/i915/i915_vma_types.h
> b/drivers/gpu/drm/i915/i915_vma_types.h
> index be6e028c3b57..b6d179bdbfa0 100644
> --- a/drivers/gpu/drm/i915/i915_vma_types.h
> +++ b/drivers/gpu/drm/i915/i915_vma_types.h
> @@ -289,6 +289,14 @@ struct i915_vma {
> /** This object's place on the active/inactive lists */
> struct list_head vm_link;
>
> + struct list_head vm_bind_link; /* Link in persistent VMA list
> */
> +
> + /** Interval tree structures for persistent vma */
Proper kerneldoc.
> + struct rb_node rb;
> + u64 start;
> + u64 last;
> + u64 __subtree_last;
> +
> struct list_head obj_link; /* Link in the object's VMA list
> */
> struct rb_node obj_node;
> struct hlist_node obj_hash;
Thanks,
Thomas
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