Re: [PATCH v9 11/12] iommu/arm-smmu-v3: Skip RMR bypass for kdump adoption
Jason Gunthorpe <[email protected]>
| Newsgroups | dev.linux.lists.iommu,org.infradead.lists.linux-arm-kernel,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <178735412603.18212.10290921432456136177.b4-review@b4> |
On Tue, 21 Jul 2026 14:38:38 -0700, Nicolin Chen <[email protected]> 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 <[email protected]> -- Jason