On Thu, Dec 08, 2022 at 06:14:01PM +1100, Alexey Kardashevskiy wrote:
> Sorry, I am not following. How is moving the bit makes
> SEV_STATUS_TO_FEATURES() not needed?
>
> When I am setting it in VMSA SEV_FEATURES - it is a bit 5.
>
> Inside a SEV VM, it is SEV_STATUS MSR and there it is bit 7. Mentioned
> MSR_AMD64_SEV* are SEV_STATUS MSR bits.
>
> Since the current patch is bad, I'd rather define the bit twice then:
Yes.
> arch/x86/include/asm/msr-index.h:
> #define MSR_AMD64_SEV_FEAT_DEBUG_SWAP BIT_ULL(7)
>
> arch/x86/include/asm/svm.h
> #define SVM_SEV_FEAT_DEBUG_SWAP BIT(5)
>
> as nothing really says that SEV_FEATURES is always going to be
> SEV_STATUS>>2, even though it is now.
>
> Soooo what is acceptable solution here? Thanks,
Right, so since you're testing against sev_status which is a copy of
MSR_AMD64_SEV, then you use bit definitions which are for that MSR as
documented in the respective PPR section for "MSRC001_0131 [SEV Status]
(Core::X86::Msr::SEV_Status)"
When you're setting the VMSA's SEV_FEATURES field, then you need a
different define, ofc.
This also automatically takes care of SEV_FEATURES not being tied to
SEV_STATUS >> 2 forever, as you say.
So yes, do the twice thing.
Thx.
--
Regards/Gruss,
Boris.
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