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Thu, 23 Apr 2026 03:14:14 -0700 (PDT) From: avinash pal To: David Woodhouse Cc: Lu Baolu , Joerg Roedel , Will Deacon , Robin Murphy , avinash pal , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Giovanni Pancotti Subject: [PATCH stable 6.12 2/2] iommu/dma: sync IOTLB before releasing IOVA on sg unmap Date: Thu, 23 Apr 2026 15:39:04 +0530 Message-ID: <20260423100904.5966-3-avinashpal441@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260423100904.5966-1-avinashpal441@gmail.com> References: <20260423100904.5966-1-avinashpal441@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On the lazy-flush path, __iommu_dma_unmap_sg() calls free_iova_fast() before iommu_iotlb_sync() has drained the old mapping from hardware. A concurrent dma_map_sg() can then allocate the same IOVA and hit the stale-PTE WARN_ON in __domain_mapping() / intel_iommu_map_pages(): CPU 0 (unmap, lazy) CPU 1 (map) ─────────────────── ───────────────────────────── iommu_unmap(iova) free_iova_fast(iova) ← live! alloc_iova_fast() → same iova __domain_mapping() dma_pte_present() == true ← WARN Fix: insert iommu_iotlb_sync() immediately before free_iova_fast() on the lazy path so the IOTLB is fully drained before IOVA reuse. The strict-mode path already serialises here; this closes the same gap for lazy/deferred flushing (regression introduced between v6.12.74 and v6.12.76 — confirmed by reporter). Reported-by: Giovanni Pancotti Link: https://bugzilla.kernel.org/show_bug.cgi?id=221389 Fixes: Cc: stable@vger.kernel.org Signed-off-by: avinash pal --- drivers/iommu/dma-iommu.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index 0f0caf590..90071cf4a 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -159,6 +159,15 @@ static void fq_ring_free_locked(struct iommu_dma_cookie *cookie, struct iova_fq break; iommu_put_pages_list(&fq->entries[idx].freelist); +/* + * Bug fix (Bugzilla #221389, regression v6.12.75/v6.12.76): + * Drain the IOTLB before handing the IOVA back to the allocator. + * On the lazy-flush path, free_iova_fast() makes the IOVA + * immediately reusable. A concurrent map() call can then receive + * the same IOVA while the old PTE is still live in hardware, + * triggering a stale-PTE WARN in __domain_mapping(). + */ +iommu_iotlb_sync(domain, &iotlb_gather); free_iova_fast(&cookie->iovad, fq->entries[idx].iova_pfn, fq->entries[idx].pages); -- 2.53.0