drm/amdkfd: Fix GPU mappings for APU after prefetch

[ Upstream commit eac32ff42393efa6657efc821231b8d802c1d485 ]

Fix the following corner case:-
 Consider a 2M huge page SVM allocation, followed by prefetch call for
the first 4K page. The whole range is initially mapped with single PTE.
After the prefetch, this range gets split to first page + rest of the
pages. Currently, the first page mapping is not updated on MI300A (APU)
since page hasn't migrated. However, after range split PTE mapping it not
valid.

Fix this by forcing page table update for the whole range when prefetch
is called.  Calling prefetch on APU doesn't improve performance. If all
it deteriotes. However, functionality has to be supported.

v2: Use apu_prefer_gtt as this issue doesn't apply to APUs with carveout
VRAM

v3: Simplify by setting the flag for all ASICs as it doesn't affect dGPU

v4: Remove v2 and v3 changes. Force update_mapping when range is split
at a size that is not aligned to prange granularity

Suggested-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Reviewed-by: Philip Yang<Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 076470b9f6f8d9c7c8ca73a9f054942a686f9ba7)
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 0d950a20741d8f914b388531216374febbae289d..99ce4fe5eb1705bc289cf50f1d10857246b7c3f0 100644 (file)
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -3675,6 +3675,8 @@ svm_range_set_attr(struct kfd_process *p, struct mm_struct *mm,
                svm_range_apply_attrs(p, prange, nattr, attrs, &update_mapping);
                /* TODO: unmap ranges from GPU that lost access */
        }
+       update_mapping |= !p->xnack_enabled && !list_empty(&remap_list);
+
        list_for_each_entry_safe(prange, next, &remove_list, update_list) {
                pr_debug("unlink old 0x%p prange 0x%p [0x%lx 0x%lx]\n",
                         prange->svms, prange, prange->start,