Re: [PATCH][retry 3] Add support for Pause Filtering to AMD SVM

Peter Zijlstra
2009-05-20T09:10:16Z

On Wed, 2009-05-20 at 12:04 +0300, Avi Kivity wrote:
> Peter Zijlstra wrote:

> >> It's a fully virtualized guest. There's no way to get this without
> >> patching the guest kernel.
> >>
> >
> > Yes there is.. virtualized monitor-wait stuff coupled with a
> > monitor-wait based spinlock implementation.
> >
>
> That only works if the guest uses monitor/mwait. Not all of the guests
> are under our control. I don't know whether Windows uses
> monitor/mwait. Further, we don't have timed exits on mwait like we do
> with pause.

Ugh, you really care about crap like windows?

> I've also heard that monitor/mwait are very slow and only usable on idle
> loop stuff.

Yeah, current implementations suck, doesn't mean it has to stay that
way.

> > Once we go change silicon, you might as well do it right.
> >
>
> None of the major x86 vendors are under my control.

I thought this patch came from AMD, who changed their silicon so 'solve'
one of these virt problems.

/me goes hide again, and pretend all of virt doesn't exist :-) Think
happy thoughts.