On 11/21/24 07:45, Sean Christopherson wrote:
> On Wed, Nov 20, 2024, Dave Hansen wrote:
>> The CPUID level dependency table will entirely zap X86_FEATURE_XSAVE
> 
> What table is that?  XSAVE depends on FXSR, but I can't find anything that clears
> X86_FEATURE_XSAVE if cpuid_level < XSTATE_CPUID.  Even if it did, dropping a
> sanity check in a one-time path adds risk for almost no reward.

arch/x86/kernel/cpu/common.c::cpuid_dependent_features[]

It's hard to find because it hard-codes the leaf number:

        { X86_FEATURE_XSAVE,            0x0000000d },

Fixing that was my initial motivation for this series.

As for removing the checks, I'd much rather have a super generic check
in the CPUID helpers that have all the callers code something.
Something like the attached patch?