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

Avi Kivity
2009-05-20T09:04:58Z

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.

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

> Once we go change silicon, you might as well do it right.
>

None of the major x86 vendors are under my control.

--
error compiling committee.c: too many arguments to function