Re: [Xen-devel] [PATCH v3 03/10] xen/arm: Implement CPU_OFF PSCI call (physical interface)

[Julien Grall <julien.grall@xxxxxxx>]

Hi Mirela,

On 27/04/18 18:12, Mirela Simonovic wrote:
> During the system suspend to RAM non-boot CPUs will be hotplugged.
> This will be triggered via disable_nonboot_cpus() call. When
> hotplugged the CPU will end up in an infinite wfi loop in stop_cpu().
> This patch adds PSCI CPU_OFF call to the EL3 with the aim to get powered
> down the calling CPU during the suspend. The CPU_OFF call will be made
> only if the PSCI version is higher than v0.1 (Note that the CPU_OFF
> function is mandatory since PSCI v0.2).
> If PSCI CPU_OFF call to the EL3 succeeds it will not return. Otherwise,
> when the PSCI CPU_OFF call returns we'll raise panic, because the
> calling CPU couldn't be enabled afterwards (stays in WFI loop forever).
> Note that if the PSCI version is higher than v0.1 the CPU_OFF will be
> called regardless of the system state. This is done because scenarios
> other than suspend may benefit from powering off the CPU.
>
> Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
>
> ---
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: Julien Grall <julien.grall@xxxxxxx>
> ---
> Changes in v2:
> -Issue PSCI CPU_OFF only if the system is suspending
> -If PSCI CPU_OFF call fails (unlikely to ever happen) raise panic
> -Fixed commit message
>
> Changes in v3:
> -Check for PSCI version prior to calling CPU_OFF
> -Don't check for system state - invoke CPU_OFF in all system states
> -Don't check if returned error is not zero because it's always not
>   zero if CPU_OFF SMC returns
> -Fixed commit message
> ---
>   xen/arch/arm/psci.c        | 13 +++++++++++++
>   xen/arch/arm/smpboot.c     |  2 ++
>   xen/include/asm-arm/psci.h |  1 +
>   3 files changed, 16 insertions(+)
>
> diff --git a/xen/arch/arm/psci.c b/xen/arch/arm/psci.c
> index 94b616df9b..7c1124e45f 100644
> --- a/xen/arch/arm/psci.c
> +++ b/xen/arch/arm/psci.c
> @@ -46,6 +46,19 @@ int call_psci_cpu_on(int cpu)
>       return call_smc(psci_cpu_on_nr, cpu_logical_map(cpu), 
> __pa(init_secondary), 0);
>   }
>   
> +void call_psci_cpu_off(void)
> +{
> +    if ( psci_ver > PSCI_VERSION(0, 1) )
> +    {
> +        int errno;
> +
> +        /* If successfull the PSCI cpu_off call doesn't return */
> +        errno = call_smc(PSCI_0_2_FN32_CPU_OFF, 0, 0, 0);
> +        panic("PSCI cpu off failed for CPU%d err=%d\n", get_processor_id(),
Please use smp_processor_id() here.

> +                errno);
The indentation looks wrong.

With that:

Acked-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,


> +    }
> +}
> +
>   void call_psci_system_off(void)
>   {
>       if ( psci_ver > PSCI_VERSION(0, 1) )
> diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
> index b2116f0d2d..8b1e274bf3 100644
> --- a/xen/arch/arm/smpboot.c
> +++ b/xen/arch/arm/smpboot.c
> @@ -395,6 +395,8 @@ void stop_cpu(void)
>       /* Make sure the write happens before we sleep forever */
>       dsb(sy);
>       isb();
> +    call_psci_cpu_off();
> +
>       while ( 1 )
>           wfi();
>   }
> diff --git a/xen/include/asm-arm/psci.h b/xen/include/asm-arm/psci.h
> index 9ac820e94a..832f77afff 100644
> --- a/xen/include/asm-arm/psci.h
> +++ b/xen/include/asm-arm/psci.h
> @@ -20,6 +20,7 @@ extern uint32_t psci_ver;
>   
>   int psci_init(void);
>   int call_psci_cpu_on(int cpu);
> +void call_psci_cpu_off(void);
>   void call_psci_system_off(void);
>   void call_psci_system_reset(void);
>   
--
Julien Grall

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