Re: [Xen-devel] [PATCH v7 15/17] vmx: VT-d posted-interrupt core logic handling

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Mon, 2015-09-21 at 11:59 +0000, Wu, Feng wrote:
> 
> > -----Original Message-----
> > From: George Dunlap [mailto:george.dunlap@xxxxxxxxxx]

> > > I think the handling for lazy context switch is not only for the
> > > blocking case,
> > > we still need to do something for lazy context switch even we
> > > handled the
> > > blocking case in vcpu_block(), such as,
> > > 1. For non-idle -> idle
> > > - set 'SN'
> > 
> > If we set SN in vcpu_block(), then we don't need to set it on
> > context
> > switch -- æäæï
> 
> For preemption case (not blocking case) , we still need to clear/set
> SN, and
> this has no business with vcpu_block()/vcpu_wake(), right? Do I miss
> something
> here? BTW, you Chinese is good! :)
> 
Well, sure, preemptions are fine being dealt with during context
switches.

AFAICR, Geoge was suggesting investigating the possibility of doing
that within the already existing arch specific part of the context
switch itself. Have you checked whether that would be possible? If yes,
it really would be great, IMO.

Note that, in case of preemptions, we are switching from a non-idle
vcpu to another, non-idle, vcpu, so lazy context switching to the idle
vcpu should not have much to do with this case... Was this something
you were saying something/asking about above? (seems so, but I can't be
sure, so I thought I better ask :-) ).

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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