Re: [PATCH] SVM: forbid guest to execute monitor/mwait

Joerg Roedel
2007-03-22T11:56:02Z

On Thu, Mar 22, 2007 at 01:40:26PM +0200, Avi Kivity wrote:
> Joerg Roedel wrote:
> >Right. But it is possible for userspace to enable monitor bit for the
> >guest. Without virtualization of these 2 instructions the guest would
> >idle in the guest state after calling mwait and prevent other processes
> >and guests from running in that time.
>
> Won't an interrupt during mwait cause a vmexit?

Yes, an interrupt would cause an vmexit. But depending on the HZ value
of the host it may be a lot of time until the next interrupt. And over
time this will sum up and slow down other tasks.

Joerg