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

[Peter Krempa]

On Thu, Nov 05, 2015 at 16:54:02 +0300, Dmitry Andreev wrote:
> 
> 
> 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.

Device or not, I don't really like having two distinct places to
configure similar functionality.

<device>
  <panic model='hyperv'/>

will do just fine IMO.

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

I concur.

Peter
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