Re: [PATCH v2 2/2] drm/amdkfd: Update mapping if range attributes changed

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Am 2022-04-22 um 18:05 schrieb Felix Kuehling:
On 2022-04-22 10:06, Philip Yang wrote:
Change SVM range mapping flags or access attributes don't trigger
migration, if range is already mapped on GPUs we should update GPU
mapping and pass flush_tlb flag true to amdgpu vm.

Change SVM range preferred_loc or migration granularity don't need
update GPU mapping, skip the validate_and_map.

Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>
---
  drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 46 +++++++++++++++++++---------
  1 file changed, 32 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 8a077cd066a1..e740384df9c7 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -686,7 +686,8 @@ svm_range_check_attr(struct kfd_process *p,
    static void
  svm_range_apply_attrs(struct kfd_process *p, struct svm_range *prange,
-              uint32_t nattr, struct kfd_ioctl_svm_attribute *attrs)
+              uint32_t nattr, struct kfd_ioctl_svm_attribute *attrs,
+              bool *update_mapping)
  {
      uint32_t i;
      int gpuidx;
@@ -702,6 +703,7 @@ svm_range_apply_attrs(struct kfd_process *p, struct svm_range *prange,
          case KFD_IOCTL_SVM_ATTR_ACCESS:
          case KFD_IOCTL_SVM_ATTR_ACCESS_IN_PLACE:
          case KFD_IOCTL_SVM_ATTR_NO_ACCESS:
+            *update_mapping = true;
              gpuidx = kfd_process_gpuidx_from_gpuid(p,
                                     attrs[i].value);
              if (attrs[i].type == KFD_IOCTL_SVM_ATTR_NO_ACCESS) {
@@ -716,9 +718,11 @@ svm_range_apply_attrs(struct kfd_process *p, struct svm_range *prange,
              }
              break;
          case KFD_IOCTL_SVM_ATTR_SET_FLAGS:
+            *update_mapping = true;
              prange->flags |= attrs[i].value;
              break;
          case KFD_IOCTL_SVM_ATTR_CLR_FLAGS:
+            *update_mapping = true;
              prange->flags &= ~attrs[i].value;
              break;
          case KFD_IOCTL_SVM_ATTR_GRANULARITY:
@@ -1254,7 +1258,7 @@ static int
  svm_range_map_to_gpu(struct kfd_process_device *pdd, struct svm_range *prange,                unsigned long offset, unsigned long npages, bool readonly,
               dma_addr_t *dma_addr, struct amdgpu_device *bo_adev,
-             struct dma_fence **fence)
+             struct dma_fence **fence, bool flush_tlb)
  {
      struct amdgpu_device *adev = pdd->dev->adev;
      struct amdgpu_vm *vm = drm_priv_to_vm(pdd->drm_priv);
@@ -1292,7 +1296,7 @@ svm_range_map_to_gpu(struct kfd_process_device *pdd, struct svm_range *prange,
               (last_domain == SVM_RANGE_VRAM_DOMAIN) ? 1 : 0,
               pte_flags);
  -        r = amdgpu_vm_update_range(adev, vm, false, false, false, NULL, +        r = amdgpu_vm_update_range(adev, vm, false, false, flush_tlb, NULL,
                         last_start, prange->start + i,
                         pte_flags,
                         last_start - prange->start,
@@ -1326,7 +1330,7 @@ svm_range_map_to_gpu(struct kfd_process_device *pdd, struct svm_range *prange,
  static int
  svm_range_map_to_gpus(struct svm_range *prange, unsigned long offset,
                unsigned long npages, bool readonly,
-              unsigned long *bitmap, bool wait)
+              unsigned long *bitmap, bool wait, bool flush_tlb)
  {
      struct kfd_process_device *pdd;
      struct amdgpu_device *bo_adev;
@@ -1361,7 +1365,8 @@ svm_range_map_to_gpus(struct svm_range *prange, unsigned long offset,             r = svm_range_map_to_gpu(pdd, prange, offset, npages, readonly,
                       prange->dma_addr[gpuidx],
-                     bo_adev, wait ? &fence : NULL);
+                     bo_adev, wait ? &fence : NULL,
+                     flush_tlb);
          if (r)
              break;
  @@ -1482,8 +1487,8 @@ static void *kfd_svm_page_owner(struct kfd_process *p, int32_t gpuidx)
   * 5. Release page table (and SVM BO) reservation
   */
  static int svm_range_validate_and_map(struct mm_struct *mm,
-                      struct svm_range *prange,
-                      int32_t gpuidx, bool intr, bool wait)
+                      struct svm_range *prange, int32_t gpuidx,
+                      bool intr, bool wait, bool flush_tlb)
  {
      struct svm_validate_context ctx;
      unsigned long start, end, addr;
@@ -1522,8 +1527,12 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
                prange->bitmap_aip, MAX_GPU_INSTANCE);
      }
  -    if (bitmap_empty(ctx.bitmap, MAX_GPU_INSTANCE))
-        return 0;
+    if (bitmap_empty(ctx.bitmap, MAX_GPU_INSTANCE)) {
+        if (!prange->mapped_to_gpu)
+            return 0;
+
+        bitmap_copy(ctx.bitmap, prange->bitmap_access, MAX_GPU_INSTANCE);
+    }
        if (prange->actual_loc && !prange->ttm_res) {
          /* This should never happen. actual_loc gets set by
@@ -1595,7 +1604,7 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
          }
            r = svm_range_map_to_gpus(prange, offset, npages, readonly,
-                      ctx.bitmap, wait);
+                      ctx.bitmap, wait, flush_tlb);
    unlock_out:
          svm_range_unlock(prange);
@@ -1691,7 +1700,7 @@ static void svm_range_restore_work(struct work_struct *work)
          mutex_lock(&prange->migrate_mutex);
            r = svm_range_validate_and_map(mm, prange, MAX_GPU_INSTANCE,
-                           false, true);
+                           false, true, false);
          if (r)
              pr_debug("failed %d to map 0x%lx to gpus\n", r,
                   prange->start);
@@ -2847,7 +2856,7 @@ svm_range_restore_pages(struct amdgpu_device *adev, unsigned int pasid,
          }
      }
  -    r = svm_range_validate_and_map(mm, prange, gpuidx, false, false);
+    r = svm_range_validate_and_map(mm, prange, gpuidx, false, false, false);
      if (r)
          pr_debug("failed %d to map svms 0x%p [0x%lx 0x%lx] to gpus\n",
               r, svms, prange->start, prange->last);
@@ -3264,6 +3273,8 @@ svm_range_set_attr(struct kfd_process *p, struct mm_struct *mm,
      struct svm_range_list *svms;
      struct svm_range *prange;
      struct svm_range *next;
+    bool update_mapping = false;
+    bool flush_tlb;
      int r = 0;
        pr_debug("pasid 0x%x svms 0x%p [0x%llx 0x%llx] pages 0x%llx\n",
@@ -3302,7 +3313,7 @@ svm_range_set_attr(struct kfd_process *p, struct mm_struct *mm,
          svm_range_add_notifier_locked(mm, prange);
      }
      list_for_each_entry(prange, &update_list, update_list) {
-        svm_range_apply_attrs(p, prange, nattr, attrs);
+        svm_range_apply_attrs(p, prange, nattr, attrs, &update_mapping);
          /* TODO: unmap ranges from GPU that lost access */
      }
      list_for_each_entry_safe(prange, next, &remove_list, update_list) { @@ -3335,8 +3346,15 @@ svm_range_set_attr(struct kfd_process *p, struct mm_struct *mm,
              continue;
          }
  +        if (!migrated && !update_mapping) {
+            mutex_unlock(&prange->migrate_mutex);
+            continue;
+        }
+
+        flush_tlb = !migrated && update_mapping && prange->mapped_to_gpu;
+

Please check that this doesn't break the XNACK off case. If a new range is created, and that does not trigger a migration or any of the conditions that set update_mapping, we still need to make sure the GPU mapping is created so that a GPU access to the new range won't fault.

Thanks for following up offline. For the record, with XNACK off, the default is "not accessible". So to create a GPU mapping, the application has to set one of the accessibility attributes, which will trigger a page table update with your patch.

The patch is

Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>



Regards,
  Felix


          r = svm_range_validate_and_map(mm, prange, MAX_GPU_INSTANCE,
-                           true, true);
+                           true, true, flush_tlb);
          if (r)
              pr_debug("failed %d to map svm range\n", r);



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