Re: [PATCH] KVM: SVM: relax conditions for allowing MSR_IA32_SPEC_CTRL accesses

[Paolo Bonzini]

On 06/02/20 15:17, Vitaly Kuznetsov wrote:
> Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> 
> but out of pure curiosity, why do we need these checks?
> 
> At least for the 'set' case right below them we have:
> 
>         if (data & ~kvm_spec_ctrl_valid_bits(vcpu))
>                  return 1;
> 
> so if guest will try using unsupported features it will #GP. So
> basically, these checks will only fire when reading/writing '0' and all
> features are missing, right? Do we care?

Probably not...  I just wanted the smallest possible change in semantics
for this patch, and the rest can be done equally on Intel and AMD.

Paolo