6.12-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Hellström thomas.hellstrom@linux.intel.com
commit 0a98219bcc961edd3388960576e4353e123b4a51 upstream.
The pnfs that we obtain from hmm_range_fault() point to pages that we don't have a reference on, and the guarantee that they are still in the cpu page-tables is that the notifier lock must be held and the notifier seqno is still valid.
So while building the sg table and marking the pages accesses / dirty we need to hold this lock with a validated seqno.
However, the lock is reclaim tainted which makes sg_alloc_table_from_pages_segment() unusable, since it internally allocates memory.
Instead build the sg-table manually. For the non-iommu case this might lead to fewer coalesces, but if that's a problem it can be fixed up later in the resource cursor code. For the iommu case, the whole sg-table may still be coalesced to a single contigous device va region.
This avoids marking pages that we don't own dirty and accessed, and it also avoid dereferencing struct pages that we don't own.
v2: - Use assert to check whether hmm pfns are valid (Matthew Auld) - Take into account that large pages may cross range boundaries (Matthew Auld)
v3: - Don't unnecessarily check for a non-freed sg-table. (Matthew Auld) - Add a missing up_read() in an error path. (Matthew Auld)
Fixes: 81e058a3e7fd ("drm/xe: Introduce helper to populate userptr") Cc: Oak Zeng oak.zeng@intel.com Cc: stable@vger.kernel.org # v6.10+ Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com Reviewed-by: Matthew Auld matthew.auld@intel.com Acked-by: Matthew Brost matthew.brost@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20250304173342.22009-3-thomas.... (cherry picked from commit ea3e66d280ce2576664a862693d1da8fd324c317) Signed-off-by: Rodrigo Vivi rodrigo.vivi@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/xe/xe_hmm.c | 120 +++++++++++++++++++++++++++++++++----------- 1 file changed, 90 insertions(+), 30 deletions(-)
--- a/drivers/gpu/drm/xe/xe_hmm.c +++ b/drivers/gpu/drm/xe/xe_hmm.c @@ -42,6 +42,42 @@ static void xe_mark_range_accessed(struc } }
+static int xe_alloc_sg(struct xe_device *xe, struct sg_table *st, + struct hmm_range *range, struct rw_semaphore *notifier_sem) +{ + unsigned long i, npages, hmm_pfn; + unsigned long num_chunks = 0; + int ret; + + /* HMM docs says this is needed. */ + ret = down_read_interruptible(notifier_sem); + if (ret) + return ret; + + if (mmu_interval_read_retry(range->notifier, range->notifier_seq)) { + up_read(notifier_sem); + return -EAGAIN; + } + + npages = xe_npages_in_range(range->start, range->end); + for (i = 0; i < npages;) { + unsigned long len; + + hmm_pfn = range->hmm_pfns[i]; + xe_assert(xe, hmm_pfn & HMM_PFN_VALID); + + len = 1UL << hmm_pfn_to_map_order(hmm_pfn); + + /* If order > 0 the page may extend beyond range->start */ + len -= (hmm_pfn & ~HMM_PFN_FLAGS) & (len - 1); + i += len; + num_chunks++; + } + up_read(notifier_sem); + + return sg_alloc_table(st, num_chunks, GFP_KERNEL); +} + /** * xe_build_sg() - build a scatter gather table for all the physical pages/pfn * in a hmm_range. dma-map pages if necessary. dma-address is save in sg table @@ -50,6 +86,7 @@ static void xe_mark_range_accessed(struc * @range: the hmm range that we build the sg table from. range->hmm_pfns[] * has the pfn numbers of pages that back up this hmm address range. * @st: pointer to the sg table. + * @notifier_sem: The xe notifier lock. * @write: whether we write to this range. This decides dma map direction * for system pages. If write we map it bi-diretional; otherwise * DMA_TO_DEVICE @@ -76,38 +113,41 @@ static void xe_mark_range_accessed(struc * Returns 0 if successful; -ENOMEM if fails to allocate memory */ static int xe_build_sg(struct xe_device *xe, struct hmm_range *range, - struct sg_table *st, bool write) + struct sg_table *st, + struct rw_semaphore *notifier_sem, + bool write) { + unsigned long npages = xe_npages_in_range(range->start, range->end); struct device *dev = xe->drm.dev; - struct page **pages; - u64 i, npages; - int ret; - - npages = xe_npages_in_range(range->start, range->end); - pages = kvmalloc_array(npages, sizeof(*pages), GFP_KERNEL); - if (!pages) - return -ENOMEM; - - for (i = 0; i < npages; i++) { - pages[i] = hmm_pfn_to_page(range->hmm_pfns[i]); - xe_assert(xe, !is_device_private_page(pages[i])); - } - - ret = sg_alloc_table_from_pages_segment(st, pages, npages, 0, npages << PAGE_SHIFT, - xe_sg_segment_size(dev), GFP_KERNEL); - if (ret) - goto free_pages; - - ret = dma_map_sgtable(dev, st, write ? DMA_BIDIRECTIONAL : DMA_TO_DEVICE, - DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_NO_KERNEL_MAPPING); - if (ret) { - sg_free_table(st); - st = NULL; + struct scatterlist *sgl; + struct page *page; + unsigned long i, j; + + lockdep_assert_held(notifier_sem); + + i = 0; + for_each_sg(st->sgl, sgl, st->nents, j) { + unsigned long hmm_pfn, size; + + hmm_pfn = range->hmm_pfns[i]; + page = hmm_pfn_to_page(hmm_pfn); + xe_assert(xe, !is_device_private_page(page)); + + size = 1UL << hmm_pfn_to_map_order(hmm_pfn); + size -= page_to_pfn(page) & (size - 1); + i += size; + + if (unlikely(j == st->nents - 1)) { + if (i > npages) + size -= (i - npages); + sg_mark_end(sgl); + } + sg_set_page(sgl, page, size << PAGE_SHIFT, 0); } + xe_assert(xe, i == npages);
-free_pages: - kvfree(pages); - return ret; + return dma_map_sgtable(dev, st, write ? DMA_BIDIRECTIONAL : DMA_TO_DEVICE, + DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_NO_KERNEL_MAPPING); }
/** @@ -235,16 +275,36 @@ int xe_hmm_userptr_populate_range(struct if (ret) goto free_pfns;
- ret = xe_build_sg(vm->xe, &hmm_range, &userptr->sgt, write); + ret = xe_alloc_sg(vm->xe, &userptr->sgt, &hmm_range, &vm->userptr.notifier_lock); if (ret) goto free_pfns;
+ ret = down_read_interruptible(&vm->userptr.notifier_lock); + if (ret) + goto free_st; + + if (mmu_interval_read_retry(hmm_range.notifier, hmm_range.notifier_seq)) { + ret = -EAGAIN; + goto out_unlock; + } + + ret = xe_build_sg(vm->xe, &hmm_range, &userptr->sgt, + &vm->userptr.notifier_lock, write); + if (ret) + goto out_unlock; + xe_mark_range_accessed(&hmm_range, write); userptr->sg = &userptr->sgt; userptr->notifier_seq = hmm_range.notifier_seq; + up_read(&vm->userptr.notifier_lock); + kvfree(pfns); + return 0;
+out_unlock: + up_read(&vm->userptr.notifier_lock); +free_st: + sg_free_table(&userptr->sgt); free_pfns: kvfree(pfns); return ret; } -