Re: [PATCH v5 09/14] x86/sev: Add Secure TSC support for SNP guests

Kirill A. Shutemov
2023-11-02T10:36:59Z

On Thu, Nov 02, 2023 at 11:11:52AM +0530, Nikunj A. Dadhania wrote:
> On 10/31/2023 1:56 AM, Tom Lendacky wrote:
> >> diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
> >> index cb0d6cd1c12f..e081ca4d5da2 100644
> >> --- a/include/linux/cc_platform.h
> >> +++ b/include/linux/cc_platform.h
> >> @@ -90,6 +90,14 @@ enum cc_attr {
> >>        * Examples include TDX Guest.
> >>        */
> >>       CC_ATTR_HOTPLUG_DISABLED,
> >> +
> >> +    /**
> >> +     * @CC_ATTR_GUEST_SECURE_TSC: Secure TSC is active.
> >> +     *
> >> +     * The platform/OS is running as a guest/virtual machine and actively
> >> +     * using AMD SEV-SNP Secure TSC feature.
> >
> > I think TDX also has a secure TSC like feature, so can this be generic?
>
> Yes, we can do that. In SNP case SecureTSC is an optional feature, not sure if that is the case for TDX as well.
>
> Kirill any inputs ?

We have several X86_FEATURE_ flags to indicate quality of TSC. Do we
really need a CC_ATTR on top of that? Maybe SEV code could just set
X86_FEATURE_ according to what its TSC can do?

--
Kiryl Shutsemau / Kirill A. Shutemov