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

Sean Christopherson
2025-01-23T18:04:18Z

On Thu, Jan 23, 2025, Borislav Petkov wrote:
> On Thu, Jan 23, 2025 at 08:25:17AM -0800, Sean Christopherson wrote:
> > But if we wanted to catch all paths, wrap the guts and clear the feature in the
> > outer layer?
>
> Yap, all valid points, thanks for catching those.
>
> > +static void __init srso_select_mitigation(void)
> > +{
> > + __srso_select_mitigation();
> >
> > if (srso_mitigation != SRSO_MITIGATION_BP_SPEC_REDUCE)
> > setup_clear_cpu_cap(X86_FEATURE_SRSO_BP_SPEC_REDUCE);
> > -
> > - pr_info("%s\n", srso_strings[srso_mitigation]);
> > }
>
> What I'd like, though, here is to not dance around this srso_mitigation
> variable setting in __srso_select_mitigation() and then know that the __
> function did modify it and now we can eval it.
>
> I'd like for the __ function to return it like __ssb_select_mitigation() does.
>
> But then if we do that, we'll have to do the same changes and turn the returns
> to "goto out" where all the paths converge. And I'd prefer if those paths
> converged anyway and not have some "early escapes" like those returns which
> I completely overlooked. :-\
>
> And that code is going to change soon anyway after David's attack vectors
> series.
>
> So, long story short, I guess the simplest thing to do would be to simply do
> the below.

I almost proposed that as well, the only reason I didn't is because I wasn't sure
what to do with the pr_info() at the end.