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

[Jan Kiszka]

On 2011-06-20 18:34, Avi Kivity wrote:
>> >
>> >  Do ILO cards / IPMI support something like this?  We could follow
>> their
>> >  lead in that case.
>>
>> 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.
> 
> 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.

Jan

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