Re: [PATCH v7 10/16] x86/sev: Add Secure TSC support for SNP guests

[Paolo Bonzini]

On Wed, Dec 20, 2023 at 4:16 PM Nikunj A Dadhania <nikunj@xxxxxxx> wrote:

> +       /* Setting Secure TSC parameters */
> +       if (cpu_feature_enabled(X86_FEATURE_SNP_SECURE_TSC)) {
> +               vmsa->tsc_scale = snp_tsc_scale;
> +               vmsa->tsc_offset = snp_tsc_offset;
> +       }

This needs to use guest_cpu_has, otherwise updating the hypervisor or
processor will change the initial VMSA and any measurement derived
from there.

In fact, the same issue exists for DEBUG_SWAP and I will shortly post
a series to allow enabling/disabling DEBUG_SWAP per-VM, so that
updating the kernel does not break existing measurements.

Paolo