[libvirt] [PATCH 1/2] conf: add crash to hyperv features

Dmitry Andreev dandreev at virtuozzo.com
Thu Nov 5 13:54:02 UTC 2015

On 05.11.2015 14:06, Jiri Denemark wrote:
> On Mon, Oct 26, 2015 at 13:23:32 +0300, Dmitry Andreev wrote:
>> Add crash CPU feature for Hyper-V. Hyper-V crash MSR's can be used
>> by Hyper-V based guests to notify about occurred guest crash.
>> XML:
>> <features>
>>    <hyperv>
>>      <crash state='on'/>
>>    </hyperv>
>> </features>
> Sounds like this is related to an existing panic device we already
> support. So what does enabling hv_crash do in QEMU? Is it an additional
> channel to a panic device or is the panic device still needed even if
> hv_crash is enabled? In any case, I think we should map this somehow to
> the panic device instead of copying 1:1 the way QEMU enables hv_crash.
pvpanic and Hyper-V crash are independent ways for guest to notify about 
OS crash. Both ways rise the 'qemu guest panicked' event. Domain can 
have both hv_crash and pvpanic enabled at the same time.

pvpanic is in <devices> section in domain configuration because it is an 
ISA device. Hyper-V crash is a hypervisor's feature, which enables a set 
of model-specific registers. Guest can use this registers to send 
notification and store additional information about a crash. This is a 
part of Microsoft hypervisor interface.

That's why I think hv_crash should be in <features> section.
> Just to make it clear, NACK until the design is sorted out.
> Jirka
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