From: Gerhard Schwanzer Date: Tue, 16 Jun 2026 10:56:06 +0000 (+0000) Subject: drm/amdkfd: Use exclusive bounds for SVM split alignment checks X-Git-Tag: v7.2-rc1~10^2~1^2~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b89d58b6595d79dc3fe75e213e1f4c5efd0251d4;p=thirdparty%2Fkernel%2Flinux.git drm/amdkfd: Use exclusive bounds for SVM split alignment checks SVM ranges use inclusive page indices: prange->last is the last page in the range. The split-remap logic introduced by commit 448ee45353ef ("drm/amdkfd: Use huge page size to check split svm range alignment") uses ALIGN_DOWN(prange->last, 512) to determine whether the original range can contain a 2MB huge-page mapping. That aligns the last page itself down. Thus a range ending one page before the next 2MB boundary is classified as if the final 2MB block did not exist. When such a range is split inside that final block, the split head or tail can be left off the remap list even though it was derived from an original range that may have PMD mappings. Use prange->last + 1 as the exclusive upper bound when computing the original range's last 2MB-aligned boundary. Then use the actual split boundary for the head and tail alignment checks: tail->start for a tail split, and new_start for a head split. new_start is equivalent to head->last + 1 and directly names the exclusive end of the split head. Using head->last for the head-side check can both remap a head that ends exactly one page before a 2MB boundary and miss a head whose split boundary is one page after such a boundary. Philip Yang pointed out in the review of the original change that this condition should use head->last + 1 or new_start. Xiaogang Chen identified the inclusive-last cause and posted the candidate fix in the regression thread. With the culprit change active and the local revert not applied, the unchanged C/HSA reproducer completes 10/10 runs with this change on an RX 7600 XT. Fixes: 448ee45353ef ("drm/amdkfd: Use huge page size to check split svm range alignment") Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/4914 Link: https://lore.kernel.org/stable/IA1PR12MB85172F7FE9157C092EDA46A0E3112@IA1PR12MB8517.namprd12.prod.outlook.com/ Link: https://lore.kernel.org/all/32ce2b72-aa16-4202-9f99-92e3cd4408bc@amd.com/ Suggested-by: Xiaogang Chen Acked-by: Alex Deucher Signed-off-by: Gerhard Schwanzer Signed-off-by: Alex Deucher (cherry picked from commit a60ea15807126b148a328051636977a33ad0e9bb) Cc: stable@vger.kernel.org --- diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c index 5a56d86b3ecf8..0900bb23349ef 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c @@ -1144,7 +1144,7 @@ static int svm_range_split_tail(struct svm_range *prange, uint64_t new_last, struct list_head *insert_list, struct list_head *remap_list) { - unsigned long last_align_down = ALIGN_DOWN(prange->last, 512); + unsigned long last_align_down = ALIGN_DOWN(prange->last + 1, 512); unsigned long start_align = ALIGN(prange->start, 512); bool huge_page_mapping = last_align_down > start_align; struct svm_range *tail = NULL; @@ -1168,7 +1168,7 @@ static int svm_range_split_head(struct svm_range *prange, uint64_t new_start, struct list_head *insert_list, struct list_head *remap_list) { - unsigned long last_align_down = ALIGN_DOWN(prange->last, 512); + unsigned long last_align_down = ALIGN_DOWN(prange->last + 1, 512); unsigned long start_align = ALIGN(prange->start, 512); bool huge_page_mapping = last_align_down > start_align; struct svm_range *head = NULL; @@ -1181,8 +1181,8 @@ svm_range_split_head(struct svm_range *prange, uint64_t new_start, list_add(&head->list, insert_list); - if (huge_page_mapping && head->last + 1 > start_align && - head->last + 1 < last_align_down && (!IS_ALIGNED(head->last, 512))) + if (huge_page_mapping && new_start > start_align && + new_start < last_align_down && !IS_ALIGNED(new_start, 512)) list_add(&head->update_list, remap_list); return 0;