Re: [PATCH] target/ppc: cpu_init: Clean up stop state on cpu reset

[Cédric Le Goater]

On 6/14/22 10:29, Frederic Barrat wrote:
> The 'resume_as_sreset' attribute of a cpu can be set when a thread is
> entering a stop state on ppc books. It causes the thread to be
> re-routed to vector 0x100 when woken up by an exception. So it must be
> cleaned on reset or a thread might be re-routed unexpectedly after a
> reset, when it was not in a stop state and/or when the appropriate
> exception handler isn't set up yet.

What is the test scenario ? and what are the symptoms ?


> Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>

Reviewed-by: Cédric Le Goater <clg@kaod.org>


> ---
>
> I didn't find an appropriate commit to add a "Fixes:". It originates
> when adding support for power management states but the code looked
> quite different in 2016 and it's not clear whether we were supporting
> reset then.

It was added when we needed some support for the POWER8 stop states.
About that time.

Thanks,

C.

> target/ppc/cpu_init.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
> index 0f891afa04..c16cb8dbe7 100644
> --- a/target/ppc/cpu_init.c
> +++ b/target/ppc/cpu_init.c
> @@ -7186,6 +7186,9 @@ static void ppc_cpu_reset(DeviceState *dev)
>           }
>           pmu_update_summaries(env);
>       }
> +
> +    /* clean any pending stop state */
> +    env->resume_as_sreset = 0;
>   #endif
>       hreg_compute_hflags(env);
>       env->reserve_addr = (target_ulong)-1ULL;