Re: [PATCH v2 1/3] xen/sched: fix adding offline cpu to cpupool

[George Dunlap <george.dunlap@xxxxxxxxx>]

On Mon, Dec 4, 2023 at 4:55 PM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 04.12.2023 16:23, Juergen Gross wrote:
> > Trying to add an offline cpu to a cpupool can crash the hypervisor,
> > as the probably non-existing percpu area of the cpu is accessed before
> > the availability of the cpu is being tested. This can happen in case
> > the cpupool's granularity is "core" or "socket".
> >
> > Fix that by testing the cpu to be online.
> >
> > Fixes: cb563d7665f2 ("xen/sched: support core scheduling for moving cpus 
> > to/from cpupools")
> > Reported-by: René Winther Højgaard <renewin@xxxxxxxxx>
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

I feel like there should be a more robust way to protect against this
sort of thing; but I don't see anything obvious, and this does fix a
bug, so:

Acked-by: George Dunlap <george.dunlap@xxxxxxxxx>