On 11/29/2012 01:13 AM, Borislav Petkov wrote:

RCX gets correctly cleaned to 0 and *then* we call CPUID.

And the asm output is the same except that RCX gets correctly cleaned up
before calling CPUID.

So what am I missing?

It doesn't matter in that context, as the surrounding MSR references
have barriers, but what I'm refering to is the "memory" barrier.

The value of ECX doesn't matter when EAX=1.

	-hpa