On 2026-09-22 17:42, Andrew Martin wrote:
CWSR ranges use the always mapped flag and only need a mapping on the GPU running the queue. However, svm_range_validate_and_map now updates the mapping on every GPU with the ACCESS attribute, which is all supported GPUs when XNACK is on. After the range is prefetched to VRAM, those GPUs may span different XGMI hives, so the page owner mismatches and is set to NULL. hmm_range_fault then tries to migrate the VRAM pages back to system memory, but svm_migrate_to_ram skips it because migrating pages back to system memory is not allowed while the GPU mapping is being updated, so the CPU page fault is never resolved. Only map to the ACCESS GPUs if the range is not mapped to any GPU and is not in VRAM.
Reviewed-by: Philip Yang <[email protected]>
Fixes: 6b2969831f7e ("drm/amdkfd: Unmap svm range from GPU set to no-access") Signed-off-by: Andrew Martin<[email protected]> Assisted-by: Claude:claude-opus-5 --- drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c index c521ec07bf3c..a99dbedf3cd4 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c @@ -1757,12 +1757,15 @@ static int svm_range_validate_and_map(struct mm_struct *mm, }/*- * If prange with always mapped flag, update mapping on GPUs with - * ACCESS attribute + * If prange with always mapped flag is not mapped or migrated + * yet, update mapping on GPUs with ACCESS attribute. Don't add + * them otherwise, ACCESS GPUs may be on different XGMI hives, + * that would force hmm_range_fault to migrate VRAM back to ram. */ - if (prange->flags & KFD_IOCTL_SVM_FLAG_GPU_ALWAYS_MAPPED) - bitmap_or(ctx->bitmap, ctx->bitmap, prange->bitmap_access, - MAX_GPU_INSTANCE); + if (bitmap_empty(ctx->bitmap, MAX_GPU_INSTANCE) && + prange->flags & KFD_IOCTL_SVM_FLAG_GPU_ALWAYS_MAPPED) + bitmap_copy(ctx->bitmap, prange->bitmap_access, + MAX_GPU_INSTANCE); } else { bitmap_or(ctx->bitmap, prange->bitmap_access, prange->bitmap_aip, MAX_GPU_INSTANCE);
