Re: [PATCH v9 11/12] iommu/arm-smmu-v3: Skip RMR bypass for kdump adoption

On Tue, 21 Jul 2026 14:38:38 -0700, Nicolin Chen [off-list ref] wrote:

RMR bypass STEs are installed during SMMUv3 probe for StreamIDs listed by
IORT RMR nodes. A normal boot switches the driver to a fresh stream table
whose initial STEs abort, so those RMR SIDs need bypass entries before it
becomes live. This preserves firmware/guest-owned traffic, including vSMMU
guest MSI cases built around RMR-described SIDs.

ARM_SMMU_OPT_KDUMP_ADOPT is the opposite case: the driver keeps SMMUEN set
and adopts the crashed kernel's stream table, so RMR SIDs already have the
only translation state known to be safe for active in-flight DMA. Replacing
an adopted STE with bypass can turn translated DMA into physical DMA, then
point it at the wrong memory.

[...]

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

-- 
Jason