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Thu, 23 Apr 2026 03:09:21 -0700 (PDT) Received: from fedora ([2401:4900:1cbc:314:9667:4972:a94c:125a]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-36140fc5d94sm25275714a91.2.2026.04.23.03.09.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Apr 2026 03:09:21 -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 Subject: [PATCH stable 6.12 0/2] iommu/vt-d+dma: fix stale DMA PTE WARN on IOVA reuse (regression v6.12.75) Date: Thu, 23 Apr 2026 15:39:02 +0530 Message-ID: <20260423100904.5966-1-avinashpal441@gmail.com> X-Mailer: git-send-email 2.53.0 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 Two-patch series addressing the stale-DMA-PTE WARN_ON regression that hits kernels 6.12.75 and 6.12.76 when Intel IOMMU is enabled. Bugzilla : https://bugzilla.kernel.org/show_bug.cgi?id=221389 Unaffected: v6.12.74 (confirmed: Giovanni Pancotti, 2026-04-22) Affected : v6.12.76 (WARN on ATA/SCSI DMA workloads) Workaround: intel_iommu=off Root cause ========== The lazy-flush path in __iommu_dma_unmap_sg() releases an IOVA back to the allocator via free_iova_fast() before iommu_iotlb_sync() drains the hardware TLB. A concurrent map() on the same domain receives the same IOVA and hits a live PTE in __domain_mapping(): CPU 0 (unmap, lazy path) CPU 1 (concurrent map) ────────────────────────── ─────────────────────────────── iommu_unmap(iova) free_iova_fast(iova) ← live alloc_iova_fast() → same iova __domain_mapping() dma_pte_present() == true WARN_ON_ONCE() ← hit Patches ======= 1/2 iommu/vt-d: fail map loudly on stale DMA PTE - Replaces bare WARN(1,...) with pr_err_ratelimited + WARN_ON_ONCE - Prints vPFN + old PTE value for debugging - Returns -EEXIST; no silent double-map 2/2 iommu/dma: sync IOTLB before releasing IOVA on sg unmap - Adds iommu_iotlb_sync() before free_iova_fast() on lazy path - Closes the race window; strict-mode path already does this ACTION NEEDED by reviewer: run git log v6.12.74..v6.12.76 -- drivers/iommu/dma-iommu.c to identify the offending commit for the Fixes: tag in patch 2/2. avinash pal (2): iommu/vt-d: fail map loudly on stale DMA PTE iommu/dma: sync IOTLB before releasing IOVA on sg unmap drivers/iommu/dma-iommu.c | 9 +++++++ drivers/iommu/intel/iommu.c | 50 ++++++++++++++++++++++++++++--------- 2 files changed, 47 insertions(+), 12 deletions(-) base-commit: 444b39ef6108313e8452010b22aaba588e8fb92b -- 2.53.0