Re: [Xen-devel] [PATCH 08/18] xen/arm: Disable/enable non-boot physical CPUs on suspend/resume

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 12 Nov 2018, Mirela Simonovic wrote:
> Non-boot CPUs have to be disabled on suspend and enabled on resume
> (hotplug-based mechanism). Disabling non-boot CPUs will lead to PSCI
> CPU_OFF to be called by each non-boot CPU. Depending on the underlying
> platform capabilities, this may lead to the physical powering down of
> CPUs. Tested on Xilinx Zynq Ultrascale+ MPSoC (including power down of
> each non-boot CPU).
> 
> Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
> Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xxxxxxxxxx>
> ---
>  xen/arch/arm/suspend.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/suspend.c b/xen/arch/arm/suspend.c
> index 575afd5eb8..dae1b1f7d6 100644
> --- a/xen/arch/arm/suspend.c
> +++ b/xen/arch/arm/suspend.c
> @@ -1,4 +1,5 @@
>  #include <xen/sched.h>
> +#include <xen/cpu.h>
>  #include <asm/cpufeature.h>
>  #include <asm/event.h>
>  #include <asm/psci.h>
> @@ -115,17 +116,29 @@ static void vcpu_suspend(register_t epoint, register_t 
> cid)
>  /* Xen suspend. Note: data is not used (suspend is the suspend to RAM) */
>  static long system_suspend(void *data)
>  {
> +    int status;
> +
>      BUG_ON(system_state != SYS_STATE_active);
>  
>      system_state = SYS_STATE_suspend;
>      freeze_domains();
>  
> +    status = disable_nonboot_cpus();
> +    if ( status )
> +    {
> +        system_state = SYS_STATE_resume;
> +        goto resume_nonboot_cpus;
> +    }
> +
>      system_state = SYS_STATE_resume;
>  
> +resume_nonboot_cpus:
> +    enable_nonboot_cpus();
>      thaw_domains();
>      system_state = SYS_STATE_active;
> +    dsb(sy);
>  
> -    return -ENOSYS;
> +    return status;
>  }

I think we need a spin_lock to protect system_suspend from concurrent
calls, or (better) we need to make sure that the caller is only allowed
to call system_suspend if there is just one vcpu active in the system,
and that vcpu is blocked on this PSCI system suspend call.


>  int32_t domain_suspend(register_t epoint, register_t cid)
> -- 
> 2.13.0
> 

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