Re: [RFC PATCH 3/7] target/i386: SEV: Add support for enabling debug-swap SEV feature

Naveen N Rao
2025-09-15T14:26:18Z

On Fri, Sep 12, 2025 at 08:50:28AM -0500, Tom Lendacky wrote:
> On 9/11/25 06:54, Naveen N Rao (AMD) wrote:
> > Add support for enabling debug-swap VMSA SEV feature in SEV-ES and
> > SEV-SNP guests through a new "debug-swap" boolean property on SEV guest
> > objects. Though the boolean property is available for plain SEV guests,
> > check_sev_features() will reject setting this for plain SEV guests.
> >
> > Add helpers for setting and querying the VMSA SEV features so that they
> > can be re-used for subsequent VMSA SEV features, and convert the
> > existing SVM_SEV_FEAT_SNP_ACTIVE definition to use the BIT() macro for
> > consistency with the new feature flag.
> >
> > Sample command-line:
> > -machine q35,confidential-guest-support=sev0 \
> > -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1,debug-swap=on
> >
> > Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
>
> Should you convert the setting/checking of SVM_SEV_FEAT_SNP_ACTIVE in the
> first patch (and wherever else it might be used), too?
>
> If you do, then it would split this into two patches, one that adds the
> helpers and converts existing accesses to sev_features and then the new
> debug_swap parameter.

Sure, I'll do that.

Thanks,
Naveen