Re: [PATCH v9 05/12] iommu/arm-smmu-v3: Add ARM_SMMU_OPT_KDUMP_ADOPT for kdump kernel

[Jason Gunthorpe]

On Tue, 21 Jul 2026 12:48:14 -0700, Nicolin Chen <nicolinc@xxxxxxxxxx> wrote:
> When transitioning to a kdump kernel, the primary kernel might have crashed
> while endpoint devices were actively bus-mastering DMA. Currently, the SMMU
> driver aggressively resets the hardware during probe by clearing CR0_SMMUEN
> and setting the Global Bypass Attribute (GBPA) to ABORT.
> 
> In a kdump scenario, this aggressive reset is highly destructive:
> a) If GBPA is set to ABORT, in-flight DMA will be aborted, generating fatal
>    PCIe AER or SErrors that may panic the kdump kernel
> b) If GBPA is set to BYPASS, in-flight DMA targeting some IOVAs will bypass
>    the SMMU and corrupt the physical memory at those 1:1 mapped IOVAs.
> 
> [...]

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

-- 
Jason