Re: [Qemu-devel] [PATCH 0/2] Introduce panic hypercall

[Gleb Natapov]

On Mon, Jun 20, 2011 at 08:23:20PM +0300, Avi Kivity wrote:
> On 06/20/2011 08:13 PM, Jan Kiszka wrote:
> >>  A watchdog has the advantage that is also detects lockups.
> >>
> >>  In fact you could implement the panic device via the existing
> >>  watchdogs.  Simply program the timer for the minimum interval and
> >>  *don't* service the interrupt.  This would work for non-virt setups as
> >>  well as another way to issue a reset.
> >
> >If you manage to bring down the other guest CPUs fast enough. Otherwise,
> >they may corrupt your crashdump before the host had a chance to collect
> >all pieces. Synchronous signaling to the hypervisor is a bit safer.
> 
> You could NMI-IPI them.  But I agree a synchronous signal is better
> (note it's not race-free itself).
> 
But kexec/kdump has exactly same race, so this is at least not worse that
alternative.

--
                        Gleb.