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charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C75A44000B X-Stat-Signature: syc137h34yy4k9pfj8ehcqj1zu7ozcyq X-HE-Tag: 1790895749-406871 X-HE-Meta: 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 ZVENs2+q 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Implement a lockless state machine using the ioptdesc's __page_refcount field. During an unmap, the driver executes atomic_sub_return() when clearing a leaf PTE. If the refcount drops to the baseline state (1), the directory is completely empty and its pointer is stored to the domain's reclaim_list Xarray. To protect against a concurrent background Shrinker pruning a directory while a map thread is actively populating it, the map thread must acquire a reference using atomic_inc_not_zero() before installing a new leaf. If the acquisition fails, the page has been marked dead (0) by the Shrinker. The map thread cleanly returns -EAGAIN, forcing the walker to loop and re-allocate a fresh directory. Only non-DMA domains are queued: DMA API unmaps can run in IRQ context and the reclaim_list lock is not IRQ safe. Signed-off-by: Pranjal Shrivastava --- drivers/iommu/generic_pt/iommu_pt.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/drivers/iommu/generic_pt/iommu_pt.h b/drivers/iommu/generic_pt/iommu_pt.h index 07ec2b3ab986..c3d09b746eec 100644 --- a/drivers/iommu/generic_pt/iommu_pt.h +++ b/drivers/iommu/generic_pt/iommu_pt.h @@ -621,6 +621,13 @@ static int __map_range_leaf(struct pt_range *range, void *arg, PT_WARN_ON(compute_best_pgsize(&pts, oa) != leaf_pgsize_lg2); } + + /* If refcount = 0, shrinker killed the page, retry map */ + if (!atomic_inc_not_zero(&virt_to_ioptdesc(pts.table)->__page_refcount)) { + ret = -EAGAIN; + break; + } + pt_install_leaf_entry(&pts, oa, leaf_pgsize_lg2, &map->attrs); oa += log2_to_int(leaf_pgsize_lg2); @@ -754,6 +761,11 @@ static __always_inline int __do_map_single_page(struct pt_range *range, if (pts.level == 0) { if (pts.type != PT_ENTRY_EMPTY) return -EADDRINUSE; + + /* If refcount = 0, shrinker killed the page, retry map */ + if (!atomic_inc_not_zero(&virt_to_ioptdesc(pts.table)->__page_refcount)) + return -EAGAIN; + pt_install_leaf_entry(&pts, map->oa, PAGE_SHIFT, &map->attrs); /* No flush, not used when incoherent */ @@ -1087,6 +1099,20 @@ static __maybe_unused int __unmap_range(struct pt_range *range, void *arg, */ num_contig_lg2 = pt_entry_num_contig_lg2(&pts); pt_clear_entries(&pts, num_contig_lg2); + + /* Drop refcount and add to reclaim_list for the last ref */ + /* + * DMA API unmaps can run in IRQ context and the reclaim_list + * lock is not IRQ safe, so only queue for non-DMA domains. + */ + if (atomic_dec_return(&virt_to_ioptdesc(pts.table)->__page_refcount) == 1 && + !iommu_is_dma_domain(&iommu_from_common(range->common)->domain)) { + struct pt_iommu *iommu = iommu_from_common(range->common); + + xa_store(&iommu->domain.reclaim_list, range->va, + virt_to_ioptdesc(pts.table), GFP_ATOMIC); + } + gather_add_leaf(&unmap->pending, &pts); num_oas += log2_to_int(num_contig_lg2); if (pts.index < flush_start_index) -- 2.56.0.rc1.315.gc6ed9934b7-goog