From: Cristian Prundeanu <cpru@amazon.com>
To: <nicolinc@nvidia.com>
Cc: <iommu@lists.linux.dev>, <jamien@nvidia.com>, <jgg@nvidia.com>,
<joro@8bytes.org>, <kas@kernel.org>, <kevin.tian@intel.com>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <praan@google.com>,
<robin.murphy@arm.com>, <smostafa@google.com>, <will@kernel.org>,
<leitao@debian.org>, Cristian Prundeanu <cpru@amazon.com>
Subject: Re: [PATCH v10 00/13] iommu/arm-smmu-v3: Adopt the crashed kernel's stream table for kdump
Date: Mon, 28 Sep 2026 10:23:02 -0500 [thread overview]
Message-ID: <20260928152302.58271-1-cpru@amazon.com> (raw)
In-Reply-To: <cover.1788130528.git.nicolinc@nvidia.com>
On Sun, Aug 30, 2026 at 04:18:01PM -0700, Nicolin Chen wrote:
> To safely absorb in-flight DMA, the kdump kernel must leave SMMUEN=1 intact
> and avoid modifying STRTAB_BASE. This allows HW to continue translating in-
> flight DMA using the crashed kernel's page tables until the endpoint device
> drivers probe and quiesce their respective hardware.
Tested v10 on AWS Graviton4 bare metal (m8g.metal-24xl: Neoverse V2, single
SMMUv3 with a 2-level stream table). On this platform, if the SMMU aborts a
NIC DMA read, firmware resets the host. An unpatched kernel fails kdump when
the NIC is still fetching from memory as the SMMU probe installs a fresh
stream table.
Reproducer: sysrq-c while the NIC receives ~100 kpps of UDP over 64 flows,
spread across most RX queues. The kdump initramfs omits the NIC driver, so
nothing quiesces the device.
Results using Amazon Linux 2023 with kdump kernel 6.18.39:
- Unpatched: 2/2 failures. The SMMU logs read and write translation aborts
~2.5 s after the panic, and the host resets before the vmcore is written.
- v7.3-rc1 + this series: 3/3 complete vmcores, no translation aborts.
The kdump kernel logs "kdump: adopting crashed kernel's stream table"
and "kdump: retaining SMMUEN for in-flight DMA". In one run the NIC
driver was present, so the device was also re-probed and reset.
Tested-by: Cristian Prundeanu <cpru@amazon.com>
prev parent reply other threads:[~2026-09-28 15:23 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-30 23:18 Nicolin Chen
2026-08-30 23:18 ` [PATCH v10 01/13] iommu/arm-smmu-v3: Init the vmid_map ida before the stream table setup Nicolin Chen
2026-08-30 23:18 ` [PATCH v10 02/13] iommu/arm-smmu-v3: Make the ASID space per SMMU instance Nicolin Chen
2026-09-23 16:39 ` Jason Gunthorpe
2026-08-30 23:18 ` [PATCH v10 03/13] iommu/arm-smmu-v3: Add ARM_SMMU_FEAT_EVTQ for the event queue Nicolin Chen
2026-09-02 11:21 ` Kiryl Shutsemau
2026-09-23 16:39 ` Jason Gunthorpe
2026-08-30 23:18 ` [PATCH v10 04/13] iommu/arm-smmu-v3: Disable the EVTQ and the PRIQ in a kdump kernel Nicolin Chen
2026-09-02 11:22 ` Kiryl Shutsemau
2026-09-23 16:39 ` Jason Gunthorpe
2026-08-30 23:18 ` [PATCH v10 05/13] iommu/arm-smmu-v3: Add strtab parse helpers to a new arm-smmu-v3-kexec.c Nicolin Chen
2026-08-30 23:18 ` [PATCH v10 06/13] iommu/arm-smmu-v3: Add ARM_SMMU_OPT_KDUMP_ADOPT for kdump kernel Nicolin Chen
2026-08-30 23:18 ` [PATCH v10 07/13] iommu/arm-smmu-v3-kexec: Add a CD table parse helper Nicolin Chen
2026-08-30 23:18 ` [PATCH v10 08/13] iommu/arm-smmu-v3-kexec: Add ASID/VMID reservation helpers Nicolin Chen
2026-09-23 16:39 ` Jason Gunthorpe
2026-08-30 23:18 ` [PATCH v10 09/13] iommu/arm-smmu-v3-kdump: Reserve crashed kernel's ASIDs and VMIDs Nicolin Chen
2026-08-30 23:18 ` [PATCH v10 10/13] iommu/arm-smmu-v3-kdump: Implement is_attach_deferred() Nicolin Chen
2026-08-30 23:18 ` [PATCH v10 11/13] iommu/arm-smmu-v3: Retain CR0_SMMUEN during kdump device reset Nicolin Chen
2026-08-30 23:18 ` [PATCH v10 12/13] iommu/arm-smmu-v3: Skip RMR bypass for kdump adoption Nicolin Chen
2026-08-30 23:18 ` [PATCH v10 13/13] iommu/arm-smmu-v3: Detect ARM_SMMU_OPT_KDUMP_ADOPT in probe() Nicolin Chen
2026-09-14 10:41 ` [PATCH v10 00/13] iommu/arm-smmu-v3: Adopt the crashed kernel's stream table for kdump Breno Leitao
2026-09-28 15:23 ` Cristian Prundeanu [this message]
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