Re: [PATCH] x86/bugs: Adjust SRSO mitigation to new features
From: Borislav Petkov
Date: Tue Nov 05 2024 - 13:57:01 EST
On Tue, Nov 05, 2024 at 10:10:20AM -0800, Sean Christopherson wrote:
> All of the actual maintainers.
Which maintainers do you mean? tip ones? If so, they're all shorted to
x86@xxxxxxxxxx.
> AFAIK, Paolo doesn't subscribe to kvm@.
Oh boy, srsly?! I thought I'd reach the proper crowd with
kvm@xxxxxxxxxxxxxxx...
> > Meh, I can split them if you really want me to.
>
> I do.
Sure, next revision.
> What does the bit actually do? I can't find any useful documentation, and the
> changelog is equally useless.
"Processors which set SRSO_MSR_FIX=1 support an MSR bit which mitigates SRSO
across guest/host boundaries. Software may enable this by setting bit
4 (BpSpecReduce) of MSR C001_102E. This bit can be set once during boot and
should be set identically across all processors in the system."
From: https://www.amd.com/content/dam/amd/en/documents/corporate/cr/speculative-return-stack-overflow-whitepaper.pdf
I think that's the only public info we have on that bit.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette