Re: [PATCH Part1 RFC v4 22/36] x86/sev: move MSR-based VMGEXITs for CPUID to helper

Borislav Petkov
2021-08-19T16:46:26Z

On Thu, Aug 19, 2021 at 10:37:41AM -0500, Michael Roth wrote:
> That makes sense, but I think it helps in making sense of the security
> aspects of the code to know that sev_cpuid() would be fetching cpuid
> information from the hypervisor.

Why is it important for the callers to know where do we fetch the CPUID
info from?

> "msr_proto" is meant to be an indicator that it will be using the GHCB
> MSR protocol to do it, but maybe just "_hyp" is enough to get the idea
> across? I use the convention elsewhere in the series as well.
>
> So sev_cpuid_hyp() maybe?

sev_cpuid_hv() pls. We abbreviate the hypervisor as HV usually.

> In "enable SEV-SNP-validated CPUID in #VC handler", it does:
>
> sev_snp_cpuid() -> sev_snp_cpuid_hyp(),
>
> which will call this with NULL e{a,b,c,d}x arguments in some cases. There
> are enough call-sites in sev_snp_cpuid() that it seemed worthwhile to
> add the guards so we wouldn't need to declare dummy variables for arguments.

Yah, saw that in the later patches.

Thx.

--
Regards/Gruss,
Boris.