[PATCH 4/5] drm/xe: Helper to populate a userptr or hmmptr
Zeng, Oak
oak.zeng at intel.com
Tue Mar 19 16:13:40 UTC 2024
> -----Original Message-----
> From: Hellstrom, Thomas <thomas.hellstrom at intel.com>
> Sent: Tuesday, March 19, 2024 4:42 AM
> To: intel-xe at lists.freedesktop.org; Zeng, Oak <oak.zeng at intel.com>
> Cc: Brost, Matthew <matthew.brost at intel.com>; Welty, Brian
> <brian.welty at intel.com>; airlied at gmail.com; Ghimiray, Himal Prasad
> <himal.prasad.ghimiray at intel.com>
> Subject: Re: [PATCH 4/5] drm/xe: Helper to populate a userptr or hmmptr
>
> On Mon, 2024-03-18 at 19:50 +0000, Zeng, Oak wrote:
> >
> >
> > > -----Original Message-----
> > > From: Hellstrom, Thomas <thomas.hellstrom at intel.com>
> > > Sent: Monday, March 18, 2024 7:54 AM
> > > To: intel-xe at lists.freedesktop.org; Zeng, Oak <oak.zeng at intel.com>
> > > Cc: Brost, Matthew <matthew.brost at intel.com>; Welty, Brian
> > > <brian.welty at intel.com>; airlied at gmail.com; Ghimiray, Himal Prasad
> > > <himal.prasad.ghimiray at intel.com>
> > > Subject: Re: [PATCH 4/5] drm/xe: Helper to populate a userptr or
> > > hmmptr
> > >
> > > Hi, Oak.
> > >
> > >
> > > On Wed, 2024-03-13 at 23:35 -0400, Oak Zeng wrote:
> > > > Add a helper function xe_hmm_populate_range to populate
> > > > a a userptr or hmmptr range. This functions calls hmm_range_fault
> > > > to read CPU page tables and populate all pfns/pages of this
> > > > virtual address range.
> > > >
> > > > If the populated page is system memory page, dma-mapping is
> > > > performed
> > > > to get a dma-address which can be used later for GPU to access
> > > > pages.
> > > >
> > > > If the populated page is device private page, we calculate the
> > > > dpa (
> > > > device physical address) of the page.
> > > >
> > > > The dma-address or dpa is then saved in userptr's sg table. This
> > > > is
> > > > prepare work to replace the get_user_pages_fast code in userptr
> > > > code
> > > > path. The helper function will also be used to populate hmmptr
> > > > later.
> > > >
> > > > Signed-off-by: Oak Zeng <oak.zeng at intel.com>
> > > > Co-developed-by: Niranjana Vishwanathapura
> > > > <niranjana.vishwanathapura at intel.com>
> > > > Signed-off-by: Niranjana Vishwanathapura
> > > > <niranjana.vishwanathapura at intel.com>
> > > > Cc: Matthew Brost <matthew.brost at intel.com>
> > > > Cc: Thomas Hellström <thomas.hellstrom at intel.com>
> > > > Cc: Brian Welty <brian.welty at intel.com>
> > > > ---
> > > > drivers/gpu/drm/xe/Makefile | 3 +-
> > > > drivers/gpu/drm/xe/xe_hmm.c | 213
> > > > ++++++++++++++++++++++++++++++++++++
> > > > drivers/gpu/drm/xe/xe_hmm.h | 12 ++
> > > > 3 files changed, 227 insertions(+), 1 deletion(-)
> > > > create mode 100644 drivers/gpu/drm/xe/xe_hmm.c
> > > > create mode 100644 drivers/gpu/drm/xe/xe_hmm.h
> > >
> > > I mostly agree with Matt's review comments on this patch. Some
> > > additional below.
> > >
> > > >
> > > > diff --git a/drivers/gpu/drm/xe/Makefile
> > > > b/drivers/gpu/drm/xe/Makefile
> > > > index 840467080e59..29dcbc938b01 100644
> > > > --- a/drivers/gpu/drm/xe/Makefile
> > > > +++ b/drivers/gpu/drm/xe/Makefile
> > > > @@ -143,7 +143,8 @@ xe-y += xe_bb.o \
> > > > xe_wait_user_fence.o \
> > > > xe_wa.o \
> > > > xe_wopcm.o \
> > > > - xe_svm_devmem.o
> > > > + xe_svm_devmem.o \
> > > > + xe_hmm.o
> > > >
> > > > # graphics hardware monitoring (HWMON) support
> > > > xe-$(CONFIG_HWMON) += xe_hwmon.o
> > > > diff --git a/drivers/gpu/drm/xe/xe_hmm.c
> > > > b/drivers/gpu/drm/xe/xe_hmm.c
> > > > new file mode 100644
> > > > index 000000000000..c45c2447d386
> > > > --- /dev/null
> > > > +++ b/drivers/gpu/drm/xe/xe_hmm.c
> > > > @@ -0,0 +1,213 @@
> > > > +// SPDX-License-Identifier: MIT
> > > > +/*
> > > > + * Copyright © 2024 Intel Corporation
> > > > + */
> > > > +
> > > > +#include <linux/mmu_notifier.h>
> > > > +#include <linux/dma-mapping.h>
> > > > +#include <linux/memremap.h>
> > > > +#include <linux/swap.h>
> > > > +#include <linux/mm.h>
> > > > +#include "xe_hmm.h"
> > > > +#include "xe_vm.h"
> > > > +
> > > > +/**
> > > > + * mark_range_accessed() - mark a range is accessed, so core mm
> > > > + * have such information for memory eviction or write back to
> > > > + * hard disk
> > > > + *
> > > > + * @range: the range to mark
> > > > + * @write: if write to this range, we mark pages in this range
> > > > + * as dirty
> > > > + */
> > > > +static void mark_range_accessed(struct hmm_range *range, bool
> > > > write)
> > >
> > > Some of the static function names aren't really unique enough not
> > > to
> > > stand in the way for a future core function name clash. Please
> > > consider
> > > using an xe_ prefix in such cases. It will also make backtraces
> > > easier
> > > to follow.
> >
> > I will add a xe_prefix for the backtrace reason...
> >
> > As I understand it, static function is file scope, so even if we have
> > a core function with
> > The same name in the future, as long as they are not in the same
> > file, there wont be any name clash...
>
> The name can't be used for a future core extern function?
Yes, at least this is my understanding of static function. Static function doesn't have a symbol so it can't clash with other static function in other file with the same name. For example, if you readelf -s xe.ko, you won't be able to find xe_mark_range_accessed, because it is a static function. I think compiler just give static function an address instead of a symbol.
Oak
>
> /Thomas
>
> >
> > >
> > >
> > > > +{
> > > > + struct page *page;
> > > > + u64 i, npages;
> > > > +
> > > > + npages = ((range->end - 1) >> PAGE_SHIFT) - (range-
> > > > >start >>
> > > > PAGE_SHIFT) + 1;
> > > > + for (i = 0; i < npages; i++) {
> > > > + page = hmm_pfn_to_page(range->hmm_pfns[i]);
> > > > + if (write) {
> > > > + lock_page(page);
> > > > + set_page_dirty(page);
> > > > + unlock_page(page);
> > >
> > > Could be using set_page_dirty_lock() here.
> >
> > Will fix, Thanks
> > Oak
> >
> > >
> > > /Thomas
> > >
> > >
> > > > + }
> > > > + mark_page_accessed(page);
> > > > + }
> > > > +}
> > > > +
> > > > +/**
> > > > + * build_sg() - build a scatter gather table for all the
> > > > physical
> > > > pages/pfn
> > > > + * in a hmm_range. dma-address is save in sg table and will be
> > > > used
> > > > to program
> > > > + * GPU page table later.
> > > > + *
> > > > + * @xe: the xe device who will access the dma-address in sg
> > > > table
> > > > + * @range: the hmm range that we build the sg table from. range-
> > > > > hmm_pfns[]
> > > > + * has the pfn numbers of pages that back up this hmm address
> > > > range.
> > > > + * @st: pointer to the sg table.
> > > > + * @write: whether we write to this range. This decides dma map
> > > > direction
> > > > + * for system pages. If write we map it bi-diretional; otherwise
> > > > + * DMA_TO_DEVICE
> > > > + *
> > > > + * All the contiguous pfns will be collapsed into one entry in
> > > > + * the scatter gather table. This is for the convenience of
> > > > + * later on operations to bind address range to GPU page table.
> > > > + *
> > > > + * The dma_address in the sg table will later be used by GPU to
> > > > + * access memory. So if the memory is system memory, we need to
> > > > + * do a dma-mapping so it can be accessed by GPU/DMA. If the
> > > > memory
> > > > + * is GPU local memory (of the GPU who is going to access
> > > > memory),
> > > > + * we need gpu dpa (device physical address), and there is no
> > > > need
> > > > + * of dma-mapping.
> > > > + *
> > > > + * FIXME: dma-mapping for peer gpu device to access remote gpu's
> > > > + * memory. Add this when you support p2p
> > > > + *
> > > > + * This function allocates the storage of the sg table. It is
> > > > + * caller's responsibility to free it calling sg_free_table.
> > > > + *
> > > > + * Returns 0 if successful; -ENOMEM if fails to allocate memory
> > > > + */
> > > > +static int build_sg(struct xe_device *xe, struct hmm_range
> > > > *range,
> > > > + struct sg_table *st, bool write)
> > > > +{
> > > > + struct device *dev = xe->drm.dev;
> > > > + struct scatterlist *sg;
> > > > + u64 i, npages;
> > > > +
> > > > + sg = NULL;
> > > > + st->nents = 0;
> > > > + npages = ((range->end - 1) >> PAGE_SHIFT) - (range-
> > > > >start >>
> > > > PAGE_SHIFT) + 1;
> > > > +
> > > > + if (unlikely(sg_alloc_table(st, npages, GFP_KERNEL)))
> > > > + return -ENOMEM;
> > > > +
> > > > + for (i = 0; i < npages; i++) {
> > > > + struct page *page;
> > > > + unsigned long addr;
> > > > + struct xe_mem_region *mr;
> > > > +
> > > > + page = hmm_pfn_to_page(range->hmm_pfns[i]);
> > > > + if (is_device_private_page(page)) {
> > > > + mr = page_to_mem_region(page);
> > > > + addr = vram_pfn_to_dpa(mr, range-
> > > > > hmm_pfns[i]);
> > > > + } else {
> > > > + addr = dma_map_page(dev, page, 0,
> > > > PAGE_SIZE,
> > > > + write ?
> > > > DMA_BIDIRECTIONAL :
> > > > DMA_TO_DEVICE);
> > > > + }
> > > > +
> > > > + if (sg && (addr == (sg_dma_address(sg) + sg-
> > > > > length))) {
> > > > + sg->length += PAGE_SIZE;
> > > > + sg_dma_len(sg) += PAGE_SIZE;
> > > > + continue;
> > > > + }
> > > > +
> > > > + sg = sg ? sg_next(sg) : st->sgl;
> > > > + sg_dma_address(sg) = addr;
> > > > + sg_dma_len(sg) = PAGE_SIZE;
> > > > + sg->length = PAGE_SIZE;
> > > > + st->nents++;
> > > > + }
> > > > +
> > > > + sg_mark_end(sg);
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/**
> > > > + * xe_hmm_populate_range() - Populate physical pages of a
> > > > virtual
> > > > + * address range
> > > > + *
> > > > + * @vma: vma has information of the range to populate. only vma
> > > > + * of userptr and hmmptr type can be populated.
> > > > + * @hmm_range: pointer to hmm_range struct. hmm_rang->hmm_pfns
> > > > + * will hold the populated pfns.
> > > > + * @write: populate pages with write permission
> > > > + *
> > > > + * This function populate the physical pages of a virtual
> > > > + * address range. The populated physical pages is saved in
> > > > + * userptr's sg table. It is similar to get_user_pages but call
> > > > + * hmm_range_fault.
> > > > + *
> > > > + * This function also read mmu notifier sequence # (
> > > > + * mmu_interval_read_begin), for the purpose of later
> > > > + * comparison (through mmu_interval_read_retry).
> > > > + *
> > > > + * This must be called with mmap read or write lock held.
> > > > + *
> > > > + * This function allocates the storage of the userptr sg table.
> > > > + * It is caller's responsibility to free it calling
> > > > sg_free_table.
> > > > + *
> > > > + * returns: 0 for succuss; negative error no on failure
> > > > + */
> > > > +int xe_hmm_populate_range(struct xe_vma *vma, struct hmm_range
> > > > *hmm_range,
> > > > + bool write)
> > > > +{
> > > > + unsigned long timeout =
> > > > + jiffies +
> > > > msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> > > > + unsigned long *pfns, flags = HMM_PFN_REQ_FAULT;
> > > > + struct xe_userptr_vma *userptr_vma;
> > > > + struct xe_userptr *userptr;
> > > > + u64 start = vma->gpuva.va.addr;
> > > > + u64 end = start + vma->gpuva.va.range;
> > > > + struct xe_vm *vm = xe_vma_vm(vma);
> > > > + u64 npages;
> > > > + int ret;
> > > > +
> > > > + userptr_vma = to_userptr_vma(vma);
> > > > + userptr = &userptr_vma->userptr;
> > > > + mmap_assert_locked(userptr->notifier.mm);
> > > > +
> > > > + npages = ((end - 1) >> PAGE_SHIFT) - (start >>
> > > > PAGE_SHIFT) +
> > > > 1;
> > > > + pfns = kvmalloc_array(npages, sizeof(*pfns),
> > > > GFP_KERNEL);
> > > > + if (unlikely(!pfns))
> > > > + return -ENOMEM;
> > > > +
> > > > + if (write)
> > > > + flags |= HMM_PFN_REQ_WRITE;
> > > > +
> > > > + memset64((u64 *)pfns, (u64)flags, npages);
> > > > + hmm_range->hmm_pfns = pfns;
> > > > + hmm_range->notifier_seq =
> > > > mmu_interval_read_begin(&userptr-
> > > > > notifier);
> > > > + hmm_range->notifier = &userptr->notifier;
> > > > + hmm_range->start = start;
> > > > + hmm_range->end = end;
> > > > + hmm_range->pfn_flags_mask = HMM_PFN_REQ_FAULT |
> > > > HMM_PFN_REQ_WRITE;
> > > > + /**
> > > > + * FIXME:
> > > > + * Set the the dev_private_owner can prevent
> > > > hmm_range_fault
> > > > to fault
> > > > + * in the device private pages owned by caller. See
> > > > function
> > > > + * hmm_vma_handle_pte. In multiple GPU case, this should
> > > > be
> > > > set to the
> > > > + * device owner of the best migration destination. e.g.,
> > > > device0/vm0
> > > > + * has a page fault, but we have determined the best
> > > > placement of
> > > > + * the fault address should be on device1, we should set
> > > > below to
> > > > + * device1 instead of device0.
> > > > + */
> > > > + hmm_range->dev_private_owner = vm->xe->drm.dev;
> > > > +
> > > > + while (true) {
> > > > + ret = hmm_range_fault(hmm_range);
> > > > + if (time_after(jiffies, timeout))
> > > > + break;
> > > > +
> > > > + if (ret == -EBUSY)
> > > > + continue;
> > > > + break;
> > > > + }
> > > > +
> > > > + if (ret)
> > > > + goto free_pfns;
> > > > +
> > > > + ret = build_sg(vm->xe, hmm_range, &userptr->sgt, write);
> > > > + if (ret)
> > > > + goto free_pfns;
> > > > +
> > > > + mark_range_accessed(hmm_range, write);
> > > > + userptr->sg = &userptr->sgt;
> > > > + userptr->notifier_seq = hmm_range->notifier_seq;
> > > > +
> > > > +free_pfns:
> > > > + kvfree(pfns);
> > > > + return ret;
> > > > +}
> > > > +
> > > > diff --git a/drivers/gpu/drm/xe/xe_hmm.h
> > > > b/drivers/gpu/drm/xe/xe_hmm.h
> > > > new file mode 100644
> > > > index 000000000000..960f3f6d36ae
> > > > --- /dev/null
> > > > +++ b/drivers/gpu/drm/xe/xe_hmm.h
> > > > @@ -0,0 +1,12 @@
> > > > +// SPDX-License-Identifier: MIT
> > > > +/*
> > > > + * Copyright © 2024 Intel Corporation
> > > > + */
> > > > +
> > > > +#include <linux/types.h>
> > > > +#include <linux/hmm.h>
> > > > +#include "xe_vm_types.h"
> > > > +#include "xe_svm.h"
> > > > +
> > > > +int xe_hmm_populate_range(struct xe_vma *vma, struct hmm_range
> > > > *hmm_range,
> > > > + bool write);
> >
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