Re: [Xen-devel] [PATCH v3 26/47] xen/sched: Change vcpu_migrate_*() to operate on schedule unit

[Jürgen Groß <jgross@xxxxxxxx>]

On 25.09.19 18:37, Dario Faggioli wrote:
> On Wed, 2019-09-25 at 14:04 +0200, Jürgen Groß wrote:
> > On 25.09.19 00:33, Dario Faggioli wrote:
> > > > As it is needed anyway call vcpu_sync_execstate() for each
> > > > vcpu of the unit when changing processors.
> > > Again, what do you mean with "As it is needed anyway"?
> > When moving from one cpu to another one the state must be saved in
> > struct vcpu (in contrast to being held partially in registers or on
> > the
> > stack in case only the idle vcpu was scheduled afterwards on the old
> > cpu).
> Sure.
>
> > This is done by vcpu_sync_execstate(). Without the explicit call
> > it would be done either when the vcpu is being scheduled on the new
> > cpu
> > or if another non-idle vcpu is becoming active on the old cpu.
> Right. And does this then means that we're now doing it twice (i.e.,
> here and either of the other places you mentioned)?
No, it checks whether it has to do anything.


Juergen

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