Re: x86: AMD Zen2 ymm registers rolling back

[Tavis Ormandy]

On Wed, Feb 22, 2023 at 11:09:51AM +0100, Borislav Petkov wrote:
> On Wed, Feb 22, 2023 at 09:38:09AM +0000, Andrew Cooper wrote:
> > This sounds suspiciously like an errata which was fixed with a ucode
> > update last year.
> 
> Yes, it looks like it.
> 
> Alternatively, you can try booting with "clearcpuid=xsaves" - that
> should take care of your observation too but yeah, you should rather
> update your microcode.
> 

Thanks - confirmed, it *doesn't* repro with 0x8301055, but does repro
with 0x830104d.

Annoyingly, I thought I was using the most recent microcode, but it seems
like there is some bug and debian wasn't applying it at boot.

That seems like a scary errata :-/

Tavis.

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