From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH 0/2] Introduce panic hypercall
Date: Tue, 21 Jun 2011 09:04:28 +0300
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Cc: Jan Kiszka <jan.kiszka@siemens.com>,
	Daniel Gollub <gollub@b1-systems.de>,
	"Daniel P. Berrange" <berrange@redhat.com>, kvm@vger.kernel.org,
	qemu-devel <qemu-devel@nongnu.org>
To: Avi Kivity <avi@redhat.com>
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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.