Re: [PATCH 0/2] Introduce panic hypercall

Gleb Natapov
2011-06-21T08:42:03Z

On Tue, Jun 21, 2011 at 11:09:21AM +0300, Avi Kivity wrote:
> On 06/21/2011 09:02 AM, Gleb Natapov wrote:
> >On Mon, Jun 20, 2011 at 07:34:57PM +0300, Avi Kivity wrote:
> >> >The only two things which came to my mind are:
> >> >
> >> > * NMI (aka. ipmitool diag) - already available in qemu/kvm - but requires
> >> > in-guest kexec/kdump
> >> > * Hardware-Watchdog (also available in qemu/libvirt)
> >>
> >> A watchdog has the advantage that is also detects lockups.
> >>
> >And has disadvantage that all time base heuristics are bite us in the
> >end.
>
> The perf-based watchdog counts clocks-not-halted, not time, so it is
> safe from time issues.
So it counts only instruction that guest actually executed? That's
perfect then. How much overhead it has in a guest though?

> We could make the hardware watchdog cheat in
> the same way.
>
Something like steal time, but for watchdog. But this become complicated fast.
Watchdog emulation will have to move into kernel for starter.

--
Gleb.