Re: [Xen-devel] [PATCH v4 08/10] xen/arm: Disable timers and release their interrupts on CPU hot-unplug

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 15/05/18 12:44, Mirela Simonovic wrote:
> When a CPU is hot-unplugged we need to disable timers and release
> their interrupts in order to free the memory that was allocated when
> interrupts were requested (using request_irq()). The request_irq()
> is called for each timer interrupt when the CPU gets hotplugged
> (start_secondary->init_timer_interrupt->request_irq).
> With this patch timers will be disabled and interrupts will be
> released when the newly added callback receives CPU_DYING event.
>
> Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,

> ---
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: Julien Grall <julien.grall@xxxxxxx>
> ---
> Changes in v3:
> -Trigger releasing of timer interrupts using notifiers
>
> Changes in v4:
> -Fix commit message to include disabling of timers
> -Disable timers prior to releasing interrupts
> -Add new line before the return in cpu_time_notifier_init()
> -Add includes alphabetically
> -Fix indentation in cpu_time_callback() definition
> ---
>   xen/arch/arm/time.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 45 insertions(+)
>
> diff --git a/xen/arch/arm/time.c b/xen/arch/arm/time.c
> index c11fcfeadd..1635c8822d 100644
> --- a/xen/arch/arm/time.c
> +++ b/xen/arch/arm/time.c
> @@ -29,6 +29,8 @@
>   #include <xen/sched.h>
>   #include <xen/event.h>
>   #include <xen/acpi.h>
> +#include <xen/cpu.h>
> +#include <xen/notifier.h>
>   #include <asm/system.h>
>   #include <asm/time.h>
>   #include <asm/vgic.h>
> @@ -312,6 +314,21 @@ void init_timer_interrupt(void)
>       check_timer_irq_cfg(timer_irq[TIMER_PHYS_NONSECURE_PPI], "NS-physical");
>   }
>   
> +/*
> + * Revert actions done in init_timer_interrupt that are required to properly
> + * disable this CPU.
> + */
> +static void deinit_timer_interrupt(void)
> +{
> +    WRITE_SYSREG32(0, CNTP_CTL_EL0);    /* Disable physical timer */
> +    WRITE_SYSREG32(0, CNTHP_CTL_EL2);   /* Disable hypervisor's timer */
> +    isb();
> +
> +    release_irq(timer_irq[TIMER_HYP_PPI], NULL);
> +    release_irq(timer_irq[TIMER_VIRT_PPI], NULL);
> +    release_irq(timer_irq[TIMER_PHYS_NONSECURE_PPI], NULL);
> +}
> +
>   /* Wait a set number of microseconds */
>   void udelay(unsigned long usecs)
>   {
> @@ -340,6 +357,34 @@ void domain_set_time_offset(struct domain *d, int64_t 
> time_offset_seconds)
>       /* XXX update guest visible wallclock time */
>   }
>   
> +static int cpu_time_callback(struct notifier_block *nfb,
> +                             unsigned long action,
> +                             void *hcpu)
> +{
> +    switch ( action )
> +    {
> +    case CPU_DYING:
> +        deinit_timer_interrupt();
> +        break;
> +    default:
> +        break;
> +    }
> +
> +    return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block cpu_time_nfb = {
> +    .notifier_call = cpu_time_callback,
> +};
> +
> +static int __init cpu_time_notifier_init(void)
> +{
> +    register_cpu_notifier(&cpu_time_nfb);
> +
> +    return 0;
> +}
> +__initcall(cpu_time_notifier_init);
> +
>   /*
>    * Local variables:
>    * mode: C
--
Julien Grall

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