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([2a09:bac6:37a8:26c8::3dd:3d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48de0bc5e0asm4806155f8f.50.2026.10.13.05.19.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Oct 2026 05:19:48 -0700 (PDT) From: Matt Fleming To: Joerg Roedel Cc: Suravee Suthikulpanit , Ashish Kalra , Vasant Hegde , Sairaj Kodilkar , Ankit Soni , Baoquan He , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@cloudflare.com, Matt Fleming Subject: [PATCH v2 0/2] iommu/amd: Fix device table setup in kdump kernels Date: Tue, 13 Oct 2026 13:19:42 +0100 Message-ID: <20261013121944.4060097-1-matt@readmodwrite.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Matt Fleming An AMD kdump kernel booted with crashkernel=512M,high and crashkernel=0,low fails to allocate its device table because there's no memory below 4G. IOMMU init fails and, on our systems with an Intel E810 NIC, the ice driver's TX queues time out, so the dump never gets sent. Since commit 38e5f33ee359 ("iommu/amd: Reuse device table for kdump"), a kdump kernel normally reuses the previous kernel's table. Patch 1 programs the new table if reuse fails. Patch 2 drops GFP_DMA32 for kdump kernels. Normal kernels still allocate below 4G, because that's what the kdump kernel checks before reusing the table. On an AMD EPYC system with an E810 NIC, the kdump kernel without these patches failed the order-9 GFP_DMA32 allocation and its TX queues timed out. With these patches, the kdump kernel reused the old device table and the dump was written over the network. The reuse-failure path in patch 1 was found by code inspection, not exercised by this test. --- Changes in v2: - Explain the split base-register write and DMA32 requirement in patch 2. - Limit patch 2's stable backports to 6.18.x and later, which contain 38e5f33ee359. - Add Ashish Kalra's and Ankit Soni's Reviewed-by tags to both patches, and Vasant Hegde's Reviewed-by tag to patch 1. - No code changes from v1. v1: https://lore.kernel.org/r/20261002133143.3628181-1-matt@readmodwrite.com Matt Fleming (2): iommu/amd: Program device table when kdump reuse fails iommu/amd: Don't allocate kdump device table from DMA32 drivers/iommu/amd/init.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) -- 2.43.0