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



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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