Re: [Xen-devel] [PATCH 0/3] VMX: Properly handle pi descriptor and per-cpu blocking list

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Dario Faggioli [mailto:dario.faggioli@xxxxxxxxxx]
> Sent: Tuesday, May 24, 2016 10:47 PM
> To: Wu, Feng <feng.wu@xxxxxxxxx>; Jan Beulich <JBeulich@xxxxxxxx>
> Cc: andrew.cooper3@xxxxxxxxxx; george.dunlap@xxxxxxxxxxxxx; Tian, Kevin
> <kevin.tian@xxxxxxxxx>; xen-devel@xxxxxxxxxxxxx; konrad.wilk@xxxxxxxxxx;
> keir@xxxxxxx
> Subject: Re: [PATCH 0/3] VMX: Properly handle pi descriptor and per-cpu
> blocking list
> 
> On Tue, 2016-05-24 at 13:33 +0000, Wu, Feng wrote:
> > > From: Wu, Feng
> > > > From: Dario Faggioli [mailto:dario.faggioli@xxxxxxxxxx]
> > > >
> > > > If a
> > > > vCPU is blocker, there is nothing to do, and in fact, nothing
> > > > happens
> > > > (as vcpu_sleep_nosync() and vcpu_wake() are NOP in that case).
> > > What do you mean by saying ' vcpu_sleep_nosync() and vcpu_wake()
> > > are NOP '?
> >
> > I think I understand what you meant above now.
> >
> Right. In any case, see the email I've just sent, with a detailed
> breakdown of the situation and of what actually happens.
> 
> > Do you think the following idea makes sense?
> >
> > When a pCPU is unplugged, we can just remove the vcpus on the
> > associated per-cpu blocking list, then we can choose another online
> > cpu, set the right NDST value, and put the vCPU the new per-cpu list?
> >
> Well, this does make sense to me, but the point is how you do that. I
> mean, how do you get to execute some PI adjustment code, from cpu-
> teardown code?
> 
> Right now, for what seemed to be necessary until now, we have the
> arch_vcpu_block(). Do we need more? If yes where?
> 
> From looking only at schedule.c, we already have arch_move_irqs(), can
> we take advantage of it?

I think we can add the logic in vmx_cpu_dead(). I've already have a draft
patch, and I will send it out to your guys to have a review later!

Thanks,
Feng

> 
> Regards,
> Dario
> --
> <<This happens because I choose it to happen!>> (Raistlin Majere)
> -----------------------------------------------------------------
> Dario Faggioli, Ph.D, http://about.me/dario.faggioli
> Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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