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

Vitaly Kuznetsov vkuznets at redhat.com
Tue Nov 10 16:54:37 UTC 2015

"Denis V. Lunev" <den at virtuozzo.com> writes:

> 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
> Please.
> 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.


while I think it would make more sense to propagate crash information
(HV_X64_MSR_CRASH_P0..P4 MSR) all the way up to libvirt (and even
further to libvirt users) instead of just triggering 'guest panic',
enabling the feature for Windows guests looks like a good starting


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