[PATCH] drm/amdgpu: use new HMM APIs and helpers
Kuehling, Felix
Felix.Kuehling at amd.com
Thu May 30 22:36:21 UTC 2019
This is a nice simplification. See a few comments inline.
On 2019-05-30 10:41 a.m., Yang, Philip wrote:
> HMM provides new APIs and helps in kernel 5.2-rc1 to simplify driver
> path. The old hmm APIs are deprecated and will be removed in future.
>
> Below are changes in driver:
>
> 1. Change hmm_vma_fault to hmm_range_register and hmm_range_fault which
> supports range with multiple vmas, remove the multiple vmas handle path
> and data structure.
> 2. Change hmm_vma_range_done to hmm_range_unregister.
> 3. Use default flags to avoid pre-fill pfn arrays.
> 4. Use new hmm_device_ helpers.
>
> Change-Id: I1a00f88459f3b96c9536933e9a17eb1ebaa78113
> Signed-off-by: Philip Yang <Philip.Yang at amd.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c | 1 -
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 140 +++++++++---------------
> 2 files changed, 53 insertions(+), 88 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
> index 41ccee49a224..e0bb47ce570b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
> @@ -519,7 +519,6 @@ void amdgpu_hmm_init_range(struct hmm_range *range)
> range->flags = hmm_range_flags;
> range->values = hmm_range_values;
> range->pfn_shift = PAGE_SHIFT;
> - range->pfns = NULL;
> INIT_LIST_HEAD(&range->list);
> }
> }
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 7138dc1dd1f4..25a9fcb409c6 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -711,8 +711,7 @@ struct amdgpu_ttm_tt {
> struct task_struct *usertask;
> uint32_t userflags;
> #if IS_ENABLED(CONFIG_DRM_AMDGPU_USERPTR)
> - struct hmm_range *ranges;
> - int nr_ranges;
> + struct hmm_range *range;
> #endif
> };
>
> @@ -725,57 +724,33 @@ struct amdgpu_ttm_tt {
> */
> #if IS_ENABLED(CONFIG_DRM_AMDGPU_USERPTR)
>
> -/* Support Userptr pages cross max 16 vmas */
> -#define MAX_NR_VMAS (16)
> -
> int amdgpu_ttm_tt_get_user_pages(struct ttm_tt *ttm, struct page **pages)
> {
> struct amdgpu_ttm_tt *gtt = (void *)ttm;
> struct mm_struct *mm = gtt->usertask->mm;
> unsigned long start = gtt->userptr;
> - unsigned long end = start + ttm->num_pages * PAGE_SIZE;
> - struct vm_area_struct *vma = NULL, *vmas[MAX_NR_VMAS];
> - struct hmm_range *ranges;
> - unsigned long nr_pages, i;
> - uint64_t *pfns, f;
> + struct vm_area_struct *vma;
> + struct hmm_range *range;
> + unsigned long i;
> + uint64_t *pfns;
> int r = 0;
>
> if (!mm) /* Happens during process shutdown */
> return -ESRCH;
>
> - down_read(&mm->mmap_sem);
> -
> - /* user pages may cross multiple VMAs */
> - gtt->nr_ranges = 0;
> - do {
> - unsigned long vm_start;
> -
> - if (gtt->nr_ranges >= MAX_NR_VMAS) {
> - DRM_ERROR("Too many VMAs in userptr range\n");
> - r = -EFAULT;
> - goto out;
> - }
> -
> - vm_start = vma ? vma->vm_end : start;
> - vma = find_vma(mm, vm_start);
> - if (unlikely(!vma || vm_start < vma->vm_start)) {
> - r = -EFAULT;
> - goto out;
> - }
> - vmas[gtt->nr_ranges++] = vma;
> - } while (end > vma->vm_end);
> -
> - DRM_DEBUG_DRIVER("0x%lx nr_ranges %d pages 0x%lx\n",
> - start, gtt->nr_ranges, ttm->num_pages);
> -
> + vma = find_vma(mm, start);
> + if (unlikely(!vma || start < vma->vm_start)) {
> + r = -EFAULT;
> + goto out;
> + }
> if (unlikely((gtt->userflags & AMDGPU_GEM_USERPTR_ANONONLY) &&
> - vmas[0]->vm_file)) {
> + vma->vm_file)) {
> r = -EPERM;
> goto out;
> }
>
> - ranges = kvmalloc_array(gtt->nr_ranges, sizeof(*ranges), GFP_KERNEL);
> - if (unlikely(!ranges)) {
> + range = kvmalloc(sizeof(*range), GFP_KERNEL | __GFP_ZERO);
A single range is pretty small. You can probably allocate that with
kmalloc now (or kcalloc/kzalloc since you specified GFP_ZERO).
> + if (unlikely(!range)) {
> r = -ENOMEM;
> goto out;
> }
> @@ -786,61 +761,52 @@ int amdgpu_ttm_tt_get_user_pages(struct ttm_tt *ttm, struct page **pages)
> goto out_free_ranges;
> }
>
> - for (i = 0; i < gtt->nr_ranges; i++)
> - amdgpu_hmm_init_range(&ranges[i]);
> + amdgpu_hmm_init_range(range);
> + range->default_flags = range->flags[HMM_PFN_VALID];
> + range->default_flags |= amdgpu_ttm_tt_is_readonly(ttm) ?
> + 0 : range->flags[HMM_PFN_WRITE];
> + range->pfn_flags_mask = 0;
> + range->pfns = pfns;
> + hmm_range_register(range, mm, start,
> + start + ttm->num_pages * PAGE_SIZE, PAGE_SHIFT);
>
> - f = ranges[0].flags[HMM_PFN_VALID];
> - f |= amdgpu_ttm_tt_is_readonly(ttm) ?
> - 0 : ranges[0].flags[HMM_PFN_WRITE];
> - memset64(pfns, f, ttm->num_pages);
> -
> - for (nr_pages = 0, i = 0; i < gtt->nr_ranges; i++) {
> - ranges[i].vma = vmas[i];
> - ranges[i].start = max(start, vmas[i]->vm_start);
> - ranges[i].end = min(end, vmas[i]->vm_end);
> - ranges[i].pfns = pfns + nr_pages;
> - nr_pages += (ranges[i].end - ranges[i].start) / PAGE_SIZE;
> + /*
> + * Just wait for range to be valid, safe to ignore return value as we
> + * will use the return value of hmm_range_fault() below under the
> + * mmap_sem to ascertain the validity of the range.
> + */
Documentation/vm/hmm.rst suggests a retry if hmm_range_fault (or
snapshot) returns -EAGAIN. I think this would be the right place to put
the again: label.
> + hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT);
>
> - r = hmm_vma_fault(&ranges[i], true);
> - if (unlikely(r))
> - break;
> - }
> - if (unlikely(r)) {
> - while (i--)
> - hmm_vma_range_done(&ranges[i]);
> + down_read(&mm->mmap_sem);
>
> - goto out_free_pfns;
> - }
> + r = hmm_range_fault(range, true);
>
> up_read(&mm->mmap_sem);
>
> + if (unlikely(r < 0))
> + goto out_free_pfns;
If r == -EAGAIN, you could goto again for a retry here as suggested by
the HMM documentation.
> +
> for (i = 0; i < ttm->num_pages; i++) {
> - pages[i] = hmm_pfn_to_page(&ranges[0], pfns[i]);
> - if (!pages[i]) {
> + pages[i] = hmm_device_entry_to_page(range, pfns[i]);
> + if (unlikely(!pages[i])) {
> pr_err("Page fault failed for pfn[%lu] = 0x%llx\n",
> i, pfns[i]);
> - goto out_invalid_pfn;
> + r = -ENOMEM;
> +
> + goto out_free_pfns;
> }
> }
> - gtt->ranges = ranges;
> + gtt->range = range;
>
> return 0;
>
> out_free_pfns:
> + hmm_range_unregister(range);
> kvfree(pfns);
> out_free_ranges:
> - kvfree(ranges);
> + kvfree(range);
If you use kmalloc/kcalloc/kzalloc above, change this to kfree.
> out:
> - up_read(&mm->mmap_sem);
> -
> return r;
> -
> -out_invalid_pfn:
> - for (i = 0; i < gtt->nr_ranges; i++)
> - hmm_vma_range_done(&ranges[i]);
> - kvfree(pfns);
> - kvfree(ranges);
> - return -ENOMEM;
> }
>
> /**
> @@ -853,23 +819,23 @@ bool amdgpu_ttm_tt_get_user_pages_done(struct ttm_tt *ttm)
> {
> struct amdgpu_ttm_tt *gtt = (void *)ttm;
> bool r = false;
> - int i;
>
> if (!gtt || !gtt->userptr)
> return false;
>
> - DRM_DEBUG_DRIVER("user_pages_done 0x%llx nr_ranges %d pages 0x%lx\n",
> - gtt->userptr, gtt->nr_ranges, ttm->num_pages);
> + DRM_DEBUG_DRIVER("user_pages_done 0x%llx pages 0x%lx\n",
> + gtt->userptr, ttm->num_pages);
>
> - WARN_ONCE(!gtt->ranges || !gtt->ranges[0].pfns,
> + WARN_ONCE(!gtt->range || !gtt->range->pfns,
> "No user pages to check\n");
>
> - if (gtt->ranges) {
> - for (i = 0; i < gtt->nr_ranges; i++)
> - r |= hmm_vma_range_done(>t->ranges[i]);
> - kvfree(gtt->ranges[0].pfns);
> - kvfree(gtt->ranges);
> - gtt->ranges = NULL;
> + if (gtt->range) {
> + r = hmm_range_valid(gtt->range);
> + hmm_range_unregister(gtt->range);
> +
> + kvfree(gtt->range->pfns);
> + kvfree(gtt->range);
> + gtt->range = NULL;
> }
>
> return r;
> @@ -953,9 +919,9 @@ static void amdgpu_ttm_tt_unpin_userptr(struct ttm_tt *ttm)
> sg_free_table(ttm->sg);
>
> #if IS_ENABLED(CONFIG_DRM_AMDGPU_USERPTR)
> - if (gtt->ranges &&
> - ttm->pages[0] == hmm_pfn_to_page(>t->ranges[0],
> - gtt->ranges[0].pfns[0]))
> + if (gtt->range &&
> + ttm->pages[0] == hmm_device_entry_to_page(gtt->range,
> + gtt->range->pfns[0]))
I think just checking gtt->range here is enough. If gtt->range is not
NULL here, we're leaking memory.
Regards,
Felix
> WARN_ONCE(1, "Missing get_user_page_done\n");
> #endif
> }
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