Re: [Xen-devel] [PATCH 2/2] xen: merge temporary vcpu pinning scenarios

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Tue, 2019-07-23 at 11:20 +0200, Juergen Gross wrote:
> Today there are three scenarios which are pinning vcpus temporarily
> to
> a single physical cpu:
> 
> - NMI/MCE injection into PV domains
> - wait_event() handling
> - vcpu_pin_override() handling
> 
> Each of those cases are handled independently today using their own
> temporary cpumask to save the old affinity settings.
>
> The three cases can be combined as the two latter cases will only pin
> a vcpu to the physical cpu it is already running on, while
> vcpu_pin_override() is allowed to fail.
> 
> So merge the three temporary pinning scenarios by only using one
> cpumask and a per-vcpu bitmask for specifying which of the three
> scenarios is currently active (they are allowed to nest).
>
Right. And, after this patch, all the three cases above and
suspend/resume, all use cpu_hard_affinity_saved.

Can you add a paragraph, either here in the changelog, on in a comment
(e.g., at the top or inside of vcpu_set_tmp_affinity()), about why this
is all fine?

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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