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

[Jason Gunthorpe]

On Tue, 21 Jul 2026 14:38:38 -0700, Nicolin Chen <nicolinc@xxxxxxxxxx> 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@xxxxxxxxxx>

-- 
Jason