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Re: [PATCH v3 8/9] x86/HVM: skip offline vCPU-s when dumping VMCBs/VMCSes


  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Date: Thu, 23 Sep 2021 16:46:52 +0200
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  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, Jun Nakajima <jun.nakajima@xxxxxxxxx>
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On Thu, Sep 23, 2021 at 01:27:30PM +0200, Jan Beulich wrote:
> On 23.09.2021 10:23, Roger Pau Monné wrote:
> > On Tue, Sep 21, 2021 at 09:20:32AM +0200, Jan Beulich wrote:
> >> There's not really any register state associated with offline vCPU-s, so
> >> avoid spamming the log with largely useless information while still
> >> leaving an indication of the fact.
> >>
> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> > 
> > Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> 
> Thanks.
> 
> > Is the state cleared when the vCPU is brought down? Or else it might
> > be interesting to print such state for debug purposes.
> 
> Hmm, if that's considered to be potentially useful, then we'd need a
> key different from VPF_down. HLT would leave state in place, and the
> INIT/SIPI sequence would clobber prior state also only on the 2nd
> step. v->is_initialised may be an option, but gets cleared by INIT,
> not SIPI. Any other ideas?

Well, I guess it's close enough. I also wonder whether we should do
something similar for PV, where it might even make more sense as you
can upload a vCPU state in that case when the vCPU is down.

Thanks, Roger.



 


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