Re: [Xen-devel] [v3 12/15] vmx: posted-interrupt handling when vCPU is blocked

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Thu, 2015-07-02 at 11:30 +0100, Andrew Cooper wrote:
> On 02/07/15 09:30, Dario Faggioli wrote:

> > It is, therefore, not effective in making sure that, even with only one
> > notification, you only kick the interested vcpu.
> >
> > This is the third time that I ask:
> >  (1) whether it is possible to have more vcpus queued on one pcpu PI 
> >      blocked list with desc.on (I really believe it is);
> >  (2) if yes, whether it is TheRightThing(TM) to kick all of them, as
> >      soon as any notification arrives, instead that putting together a
> >      mechanism for kicking only a specific one.
> 
> We will receive one NV for every time the hardware managed to
> successfully set desc.on
> 
Right, I see it now, thanks.

> If multiple stack up and we proactively drain the list, we will
> subsequently search the list to completion for all remaining NV's, due
> to finding no appropriate entries.
> 
> I can't currently decide whether this will be quicker or slower overall,
> or (most likely) it will even out to equal in the general case.
> 
Well, given the thing works as you (two) just described, I think
draining the list is the only thing we can do.

In fact, AFAICT, since we can't know for what vcpu a particular
notification is intended, we don't have alternatives to waking them all,
do we?

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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