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

Denis V. Lunev den at virtuozzo.com
Tue Nov 10 16:02:06 UTC 2015

On 11/10/2015 06:55 PM, Dmitry Andreev wrote:
> Paolo, Jiri, can I do something more for this patch to be accepted?
> On 05.11.2015 17:32, Paolo Bonzini wrote:
>> On 05/11/2015 14:54, 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.
>> I agree.
>> Paolo

This feature is very interesting for us for guest debugging
especially during guest installation where specific drivers
are not available or not ready or not that easy to supply.


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