Re: [PATCH 8/8] x86, cleanups: Simplify sync_core() in the case of no CPUID

[Linus Torvalds]

On Thu, Nov 29, 2012 at 1:24 PM, H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> wrote:
>
> Thinking about it some more, there is another reason to not do this,
> which is that we don't want this particular CPUID to be paravirtualized;
> we're after the synchronizing side effect, not the CPUID return value
> itself.
>
> So let's leave it as a primitive; it gets too confusing otherwise.

Hmm. The virtualization issue brings up another point: do we *really*
want to use cpuid for serialization at all?

Exactly because under _real_ virtualization (as opposed to para-virt),
it can cause unnecessary exits in a virtualized environment, no?

So I'm wondering if there is any better synchronizing instruction..

I guess sync_core() isn't used *that* much, so maybe we don't care,
but I thought I'd ask...

                Linus
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