Re: [PATCH v4 1/2] x86/sev: Clear RMPOPT when segmented RMP is disabled by firmware

[Borislav Petkov <bp@alien8.de>]

On Mon, Nov 02, 2026 at 03:25:52PM -0600, Tom Lendacky wrote:
> The current code clears X86_FEATURE_RMPOPT when
> probe_segmented_rmptable_info() fails. The above code doesn't.

See the hunk in cpuid-deps.c

> But since SNP will be disabled on failure of snp_probe_rmptable_info(),
> I guess it doesn't matter. In which case you can eliminate the goto by
> doing:

> 
> 	if (cpu_feature_enabled(X86_FEATURE_SEGMENTED_RMP)) {
> 		rdmsrq(MSR_AMD64_RMP_CFG, rmp_cfg);
> 		if (rmp_cfg & MSR_AMD64_SEG_RMP_ENABLED)
> 			return probe_segmented_rmptable_info();
> 	}
> 
> 	setup_clear_cpu_cap(X86_FEATURE_RMPOPT);
> 	return probe_contiguous_rmptable_info();
> 
> Which looks pretty clean.

Yap.

> > diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
> > index 99801e844b30..acbcec394ef1 100644
> > --- a/arch/x86/kernel/cpu/cpuid-deps.c
> > +++ b/arch/x86/kernel/cpu/cpuid-deps.c
> > @@ -93,6 +93,7 @@ static const struct cpuid_dep cpuid_deps[] = {
> >  	{ X86_FEATURE_SPEC_CTRL_SSBD,		X86_FEATURE_SPEC_CTRL },
> >  	{ X86_FEATURE_LASS,			X86_FEATURE_SMAP      },
> >  	{ X86_FEATURE_INVLPGB,			X86_FEATURE_PCID      },
> > +	{ X86_FEATURE_RMPOPT,			X86_FEATURE_SEV_SNP   },

This hunk.

-- 
Regards/Gruss,
    Boris.

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