[PATCH] powerpc/pseries: unregister VPA when hot unplugging a CPU

[Michael Ellerman]

On Mon, 14 Nov 2022 17:01:50 +0100, Laurent Dufour wrote:
> The VPA should unregister when offlining a CPU. Otherwise there could be a
> short window where 2 CPUs could share the same VPA.
> 
> This happens because the hypervisor is still keeping the VPA attached to
> the vCPU even if it became offline.
> 
> Here is a potential situation:
>  1. remove proc A,
>  2. add proc B. If proc B gets proc A's place in cpu_present_map, then it
>     registers proc A's VPAs.
>  3. If proc B is then re-added to the LP, its threads are sharing VPAs with
>     proc A briefly as they come online.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/pseries: unregister VPA when hot unplugging a CPU
      https://git.kernel.org/powerpc/c/f6aa37c51ec0d053ee34c235bfe0e666618a3baf

cheers