Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation

[Linus Torvalds]

On Fri, Dec 2, 2016 at 10:03 AM, Borislav Petkov <bp@xxxxxxxxxx> wrote:
>
> SNB:
> * before:
> * after:

I suspect it's entirely invisible on raw hardware. But quite possibly
more noticeable in a VM that takes slow faults for every case.

But yes, even there is' probably not *that* noticeable.

I'd prefer to get rid of them just because I don't like voodoo
programming. If there is no actual reason for "sync_core()", we
shouldn't have one there. Even if it were entirely free and the
compiler optimized it away because the compiler was so smart that it
would see that it's pointless, it's misleading and wrong on a source
level.

That is, of course, assuming that there  is no really subtle reason
why that stupid sync_core() is there.

      Linus