Re: [PATCH v2 3/4] x86/bugs: KVM: Add support for SRSO_MSR_FIX

Borislav Petkov
2025-01-08T19:45:42Z

On Wed, Jan 08, 2025 at 11:43:14AM -0800, Jim Mattson wrote:
> > We don't need safe-RET with SRSO_USER_KERNEL_NO=1. And there's no safe-RET for
> > virt only. So IBPB-on-VMEXIT is the next best thing. The good thing is, those
> > machines have BpSpecReduce too so you won't be doing IBPB-on-VMEXIT either but
> > what we're talking about here - BpSpecReduce.
>
> I'm suggesting that IBPB-on-VMexit is probably the *worst* thing.

I know what you're suggesting and I don't think so but I'd need to look at the
numbers.

> If it weren't for BpSpecReduce, I would want safe-RET for virt only.

Read my reply again.

> (Well, if it weren't for ASI, I would want that, anyway.)

I'm sure Brendan is waiting for reviews there.

--
Regards/Gruss,
Boris.