drm/amdkfd: Remove prefault before migrating to VRAM

Prefaulting potentially allocates system memory pages before a
migration. This adds unnecessary overhead. Instead we can skip
unallocated pages in the migration and just point migrate->dst to a
0-initialized VRAM page directly. Then the VRAM page will be inserted
to the PTE. A subsequent CPU page fault will migrate the page back to
system memory.

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
index 6555d77..929dec1 100644 (file)
--- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
@@ -322,12 +322,13 @@ svm_migrate_copy_to_vram(struct amdgpu_device *adev, struct svm_range *prange,
        for (i = j = 0; i < npages; i++) {
                struct page *spage;
 
+               dst[i] = cursor.start + (j << PAGE_SHIFT);
+               migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
+               svm_migrate_get_vram_page(prange, migrate->dst[i]);
+               migrate->dst[i] = migrate_pfn(migrate->dst[i]);
+
                spage = migrate_pfn_to_page(migrate->src[i]);
                if (spage && !is_zone_device_page(spage)) {
-                       dst[i] = cursor.start + (j << PAGE_SHIFT);
-                       migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
-                       svm_migrate_get_vram_page(prange, migrate->dst[i]);
-                       migrate->dst[i] = migrate_pfn(migrate->dst[i]);
                        src[i] = dma_map_page(dev, spage, 0, PAGE_SIZE,
                                              DMA_TO_DEVICE);
                        r = dma_mapping_error(dev, src[i]);
@@ -522,9 +523,6 @@ svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t best_loc,
        pr_debug("svms 0x%p [0x%lx 0x%lx] to gpu 0x%x\n", prange->svms,
                 prange->start, prange->last, best_loc);
 
-       /* FIXME: workaround for page locking bug with invalid pages */
-       svm_range_prefault(prange, mm, SVM_ADEV_PGMAP_OWNER(adev));
-
        start = prange->start << PAGE_SHIFT;
        end = (prange->last + 1) << PAGE_SHIFT;
 

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 11074cc..cf5b400 100644 (file)
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -3181,28 +3181,6 @@ out:
        return best_loc;
 }
 
-/* FIXME: This is a workaround for page locking bug when some pages are
- * invalid during migration to VRAM
- */
-void svm_range_prefault(struct svm_range *prange, struct mm_struct *mm,
-                       void *owner)
-{
-       struct hmm_range *hmm_range;
-       int r;
-
-       if (prange->validated_once)
-               return;
-
-       r = amdgpu_hmm_range_get_pages(&prange->notifier, mm, NULL,
-                                      prange->start << PAGE_SHIFT,
-                                      prange->npages, &hmm_range,
-                                      false, true, owner);
-       if (!r) {
-               amdgpu_hmm_range_get_pages_done(hmm_range);
-               prange->validated_once = true;
-       }
-}
-
 /* svm_range_trigger_migration - start page migration if prefetch loc changed
  * @mm: current process mm_struct
  * @prange: svm range structure

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
index cfac13a..012c537 100644 (file)
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
@@ -181,8 +181,6 @@ void schedule_deferred_list_work(struct svm_range_list *svms);
 void svm_range_dma_unmap(struct device *dev, dma_addr_t *dma_addr,
                         unsigned long offset, unsigned long npages);
 void svm_range_free_dma_mappings(struct svm_range *prange);
-void svm_range_prefault(struct svm_range *prange, struct mm_struct *mm,
-                       void *owner);
 int svm_range_get_info(struct kfd_process *p, uint32_t *num_svm_ranges,
                       uint64_t *svm_priv_data_size);
 int kfd_criu_checkpoint_svm(struct kfd_process *p,