Re: [Xen-devel] [PATCH v3] xen: fix reboot/shutdown with running HVM guests

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: Thursday, June 05, 2014 9:16 AM
> 
> On 05/06/14 17:02, Jan Beulich wrote:
> >>>> On 05.06.14 at 17:46, <andrew.cooper3@xxxxxxxxxx> wrote:
> >> On 05/06/14 16:01, Roger Pau Monne wrote:
> >>> If there's a guest using VMX/SVM when the hypervisor shuts down, it
> >>> can lead to the following crash due to VMX/SVM functions being called
> >>> after hvm_cpu_down has been called. In order to prevent that, check in
> >>> {svm/vmx}_ctxt_switch_from that the cpu virtualization extensions are
> >>> still enabled.
> >> I feel that this is still trying to fix the problem from the wrong end.
> >> It is incorrect to be in a context switch at the point identified in the
> >> stack trace.
> >>
> >> How about having the hvm_cpu_down functions look at current, and
> >> optionally run sync_exec_state() ?
> > I considered this too before suggesting the other alternative,
> > but why would getting into the context switch path this way
> > be any better than through map_domain_page()?
> >
> > Jan
> >
> 
> It is a more controlled point on all shutdown/crash paths, but still not
> perfect.
> 
> What we probably need on all shutdown paths is an early step of
> "reschedule the idle vcpu back on all pcpus".  This won't fix the issue
> for crash paths however.
> 

possibly we'll need both. I'll go to ack the patch anyway, since the check
itself still makes sense there.

Thanks
Kevin

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