Re: [RFC v2 01/17] x86/apic: Add new driver for Secure AVIC

Borislav Petkov
2025-04-07T13:17:48Z

On Wed, Apr 02, 2025 at 04:04:34PM +0530, Neeraj Upadhyay wrote:
> - snp_get_unsupported_features() looks like below.
> It checks that, for the feature bits which are part of SNP_FEATURES_IMPL_REQ,
> if they are enabled in hypervisor (and so reported in sev_status),
> guest need to implement/enable those features. SAVIC also falls in that category
> of SNP features.
>
> So, if CONFIG_AMD_SECURE_AVIC is disabled, guest would run with SAVIC feature
> disabled in guest. This would cause undefined behavior for that guest if SAVIC
> feature is active for that guest in hypervisor.

Ok, so SNP_FEATURES_IMPL_REQ will contain the SAVIC bit (unconditionally,
without the ifdeffery) and SNP_FEATURES_PRESENT will contain that thing you
had suggested with the ifdeffery to denote whether SAVIC support has been
enabled at build time:

https://lore.kernel.org/r/e0362a96-4b3a-44b1-8d54-806a6b045799@amd.com

or not.

Right?

--
Regards/Gruss,
Boris.