Re: [PATCH 0/2] iommu/amd: Use MAX buffer size when SNP is enabled on Family 0x19

[Usama Arif <usama.arif@linux.dev>]

On Thu, 13 Aug 2026 19:28:55 +0530 Vasant Hegde <vasant.hegde@amd.com> wrote:

> Usama,
> 
> On 8/13/2026 6:48 PM, Usama Arif wrote:
> > [You don't often get email from usama.arif@linux.dev. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> > 
> > On Mon, 20 Apr 2026 08:42:02 +0000 Vasant Hegde <vasant.hegde@amd.com> wrote:
> > 
> >> This series addresses CVE-2023-20585 [1] by increasing the AMD IOMMU
> >> Event log and PPR log buffer sizes to the maximum supported value (512K)
> >> on affected CPU families when SNP is enabled.
> >>
> >> Use MAX buffer size when SNP is enabled on Milan/Genoa. Impacted buffers:
> >>   - Milan : Event log (PPR/GALog is not supported when SNP is enabled)
> >>   - Genoa : Event and PPR log (GALog is not supported when SNP is enabled)
> >>
> > 
> > Hi,
> > 
> > This series seems to break kexec in our production on Milan hosts with SEV enabled.
> > This is on the 6.18.43 stable kernel backport.
> 
> Do you have dmesg?
> 
> > 
> > If on top of 6.18.43 release, we revert the 2 commits, i.e.
> > Revert "iommu/amd: Use maximum PPR log buffer size when SNP is enabled on Family 0x19"
> > Revert "iommu/amd: Use maximum Event log buffer size when SNP is enabled on Family 0x19"
> > 
> > kexec starts working again.
> > > Could you help in fixing this issue?
> 
> Sure. We will try to reproduce it internally and get back to you.

Hi,

Just following up, were you able to reproduce this?

I was able to trace down the hang to this do while loop [1].

Could this be a firmware bug? We are currently running 1.53 (below
shows up in the dmesg).

[   22.245942] ccp 0000:41:00.1: SEV-SNP API:1.53 build:5
[   22.308933] ccp 0000:41:00.1: SEV API:1.53 build:5

[1] https://elixir.bootlin.com/linux/v7.2/source/arch/x86/virt/svm/sev.c#L1017

Thanks,
Usama

> 
> -Vasant
> 
>