Re: [Xen-devel] Fwd: [v3 14/15] Update Posted-Interrupts Descriptor during vCPU scheduling

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Mon, 2015-06-29 at 18:36 +0100, Andrew Cooper wrote:

> 
> The basic idea here is:
> 1. When vCPU's state is RUNSTATE_running,
>         - set 'NV' to 'Notification Vector'.
>         - Clear 'SN' to accpet PI.
>         - set 'NDST' to the right pCPU.
> 2. When vCPU's state is RUNSTATE_blocked,
>         - set 'NV' to 'Wake-up Vector', so we can wake up the
>           related vCPU when posted-interrupt happens for it.
>         - Clear 'SN' to accpet PI.
> 3. When vCPU's state is RUNSTATE_runnable/RUNSTATE_offline,
>         - Set 'SN' to suppress non-urgent interrupts.
>           (Current, we only support non-urgent interrupts)
>         - Set 'NV' back to 'Notification Vector' if needed.
> 
It might be me, but it feels a bit odd to see RUNSTATE-s being (ab)used
directly for this, as it does feel odd to see arch specific code being
added in there.

Can't this be done in context_switch(), which is already architecture
specific? I was thinking to something very similar to what has been done
for PSR, i.e., on x86, put everything in __context_switch().

Looking at who's prev and who's next, and at what pause_flags each has
set, you should be able to implement all of the above logic.

Or am I missing something?

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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