Re: [PATCH v4 2/4] iommu/amd: Reuse device table for kdump

[Sairaj Kodilkar]

On 7/22/2025 3:23 AM, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@xxxxxxx>
>
> After a panic if SNP is enabled in the previous kernel then the kdump
> kernel boots with IOMMU SNP enforcement still enabled.
>
> IOMMU device table register is locked and exclusive to the previous
> kernel. Attempts to copy old device table from the previous kernel
> fails in kdump kernel as hardware ignores writes to the locked device
> table base address register as per AMD IOMMU spec Section 2.12.2.1.
>
> This results in repeated "Completion-Wait loop timed out" errors and a
> second kernel panic: "Kernel panic - not syncing: timer doesn't work
> through Interrupt-remapped IO-APIC".
>
> Reuse device table instead of copying device table in case of kdump
> boot and remove all copying device table code.
>
> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>

Tested-by: Sairaj Kodilkar <sarunkod@xxxxxxx>