Re: [PATCH] xen: arm: Don't use stop_cpu() in halt_this_cpu()

[Julien Grall <julien@xxxxxxx>]

Hi Dmitry,

On 23/06/2022 08:44, dmitry.semenets@xxxxxxxxx wrote:
> From: Dmytro Semenets <dmytro_semenets@xxxxxxxx>
>
> When shutting down (or rebooting) the platform, Xen will call stop_cpu()
> on all the CPUs but one. The last CPU will then request the system to
> shutdown/restart.
>
> On platform using PSCI, stop_cpu() will call PSCI CPU off. Per the spec
> (section 5.5.2 DEN0022D.b), the call could return DENIED if the Trusted
> OS is resident on the CPU that is about to be turned off.
>
> As Xen doesn't migrate off the trusted OS (which BTW may not be
> migratable), it would be possible to hit the panic().
>
> In the ideal situation, Xen should migrate the trusted OS or make sure
> the CPU off is not called. However, when shutting down (or rebooting)
> the platform, it is pointless to try to turn off all the CPUs (per
> section 5.10.2, it is only required to put the core in a known state).
>
> So solve the problem by open-coding stop_cpu() in halt_this_cpu() and
> not call PSCI CPU off.
>
> Signed-off-by: Dmytro Semenets <dmytro_semenets@xxxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

And committed.

Cheers,

--
Julien Grall