Re: [Xen-devel] [PATCH v8 15/17] vmx: VT-d posted-interrupt core logic handling

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Tue, 2015-10-27 at 03:51 -0600, Jan Beulich wrote:
> > > > On 27.10.15 at 06:19, <feng.wu@xxxxxxxxx> wrote:
> > > From: Dario Faggioli [mailto:dario.faggioli@xxxxxxxxxx]
> > > Sent: Monday, October 26, 2015 10:40 PM
> > > In any case, it would have been nice, given the situation, if
> > > you'd have put a few
> > > words about, e.g., which solution you ended up implementing and
> > > why, either in
> > > the cover or here (e.g., in the '---' area).
> > 
> > Thanks for the suggestion. As I mentioned before, updating the PI
> > descriptor 
> > needs
> > to be atomic, I think it should be a little expensive. So doing it
> > every 
> > VM-exit seems
> > not a good idea to me.
> 
> You could check whether any update is needed before doing the
> (atomic) cmpxchg16b.
> 
Indeed! Do we have enough state, when in the VMX entry/exit handlers,
to check that? If yes, I really think this solution is worth at least a
try.

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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