Re: [Xen-devel] [PATCH v3 3/4] x86/hvm: Add HVM-specific hypervisor CPUID leaf

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 03/14/2014 04:14 AM, Jan Beulich wrote:
> > > > On 13.03.14 at 19:08, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
> > +void hvm_hypervisor_cpuid_leaf(uint32_t idx, uint32_t sub_idx,
> > +                               uint32_t *eax, uint32_t *ebx,
> > +                               uint32_t *ecx, uint32_t *edx)
> > +{
> > +    if ( idx != 4 )
> > +        return;
> What's the point of this check?
Indeed unnecessary, this is already checked at the caller.

> Why is "idx" being passed in here in
> the first place? With you making use of "sub_idx", there's absolutely
> no reason to expect the need for another leaf to ever get funneled
> into here.
I am passing the arguments directly from cpuid_hypervisor_leaves() which
already has idx and sub_idx and I wasn't sure I can assume that they will be
in eax and ecx (which they currently are).

As for sub_idx, I thought that at some point in the future we we might 
use it
so I kept it. But I can drop it since it's rather unlikely.


-boris

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