Re: [Xen-devel] driver domain crash and reconnect handling

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

On 24/01/13 09:59, Ian Campbell wrote:
> > Actually I've used the xc_domain_resume_any() function from libxc to
> > resume the guests. It worked with PV guests, however with some hacks in
> > the hypervisor to silently discarding the error condicions, and not
> > returning from the hypercall with an error. The two guests I've used,
> > and their problems with the hypercall return values:
> >
> > - SLES 11 SP1 (2.6.32.12) crashes because VCPUOP_register_vcpu_info
> > hypercall returns EINVAL, as ( v->arch.vcpu_info_mfn != INVALID_MFN )
> > - Debian Squeeze 6.0 (2.6.32-5) crashes because EVTCHNOP_bind_virq
> > returns EEXISTS, as ( v->virq_to_evtchnvirq != 0 )
> > - (these hypercalls were made right after guest comes back from the
> > suspend hypercall)
> The toolstack might need to do EVTCHNOP_reset or do some other cleanup?
Yep, that might be an another solution, to reset these values from 
toolstack via hypercall(s), but as far as I checked all the current 
hypercalls which are changing these things, doing a lot of other stuff 
which we not necessarily want. So it might be necessary to define a new 
hypercall specifically for this use-case. Probably it's easier than make 
Xen aware that a suspend/resume happened, and the guest remained in the 
same domain.
> Pausing guests when one of their supporting driver domains goes away
> does seem like a good idea.
>
> I suppose the flip side is that a domain which isn't using a disk which
> goes away briefly would see a hiccup it wouldn't have otherwise seen.
Well, I think it would be quite complicated to watch the ring buffer for 
activities while there is no backend connected. I would say this is an 
acceptable loss.
Zoli

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