Re: [PATCH] LoongArch: Add irq_work support via self IPIs

[Huacai Chen]

On Thu, May 16, 2024 at 8:23 PM maobibo <maobibo@xxxxxxxxxxx> wrote:
>
>
>
> On 2024/5/14 下午3:32, Huacai Chen wrote:
> > Add irq_work support for LoongArch via self IPIs. This make it possible
> > to run works in hardware interrupt context, which is a prerequisite for
> > NOHZ_FULL.
> >
> > Implement:
> >   - arch_irq_work_raise()
> >   - arch_irq_work_has_interrupt()
> >
> > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> > ---
> >   arch/loongarch/include/asm/hardirq.h  |  3 ++-
> >   arch/loongarch/include/asm/irq_work.h | 10 ++++++++++
> >   arch/loongarch/include/asm/smp.h      |  2 ++
> >   arch/loongarch/kernel/paravirt.c      |  6 ++++++
> >   arch/loongarch/kernel/smp.c           | 14 ++++++++++++++
> >   5 files changed, 34 insertions(+), 1 deletion(-)
> >   create mode 100644 arch/loongarch/include/asm/irq_work.h
> >
> > diff --git a/arch/loongarch/include/asm/hardirq.h b/arch/loongarch/include/asm/hardirq.h
> > index d41138abcf26..1d7feb719515 100644
> > --- a/arch/loongarch/include/asm/hardirq.h
> > +++ b/arch/loongarch/include/asm/hardirq.h
> > @@ -12,11 +12,12 @@
> >   extern void ack_bad_irq(unsigned int irq);
> >   #define ack_bad_irq ack_bad_irq
> >
> > -#define NR_IPI       2
> > +#define NR_IPI       3
> >
> >   enum ipi_msg_type {
> >       IPI_RESCHEDULE,
> >       IPI_CALL_FUNCTION,
> > +     IPI_IRQ_WORK,
> >   };
> >
> >   typedef struct {
> > diff --git a/arch/loongarch/include/asm/irq_work.h b/arch/loongarch/include/asm/irq_work.h
> > new file mode 100644
> > index 000000000000..d63076e9160d
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/irq_work.h
> > @@ -0,0 +1,10 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef _ASM_LOONGARCH_IRQ_WORK_H
> > +#define _ASM_LOONGARCH_IRQ_WORK_H
> > +
> > +static inline bool arch_irq_work_has_interrupt(void)
> > +{
> > +     return IS_ENABLED(CONFIG_SMP);
> > +}
> > +
> > +#endif /* _ASM_LOONGARCH_IRQ_WORK_H */
> > diff --git a/arch/loongarch/include/asm/smp.h b/arch/loongarch/include/asm/smp.h
> > index 278700cfee88..50db503f44e3 100644
> > --- a/arch/loongarch/include/asm/smp.h
> > +++ b/arch/loongarch/include/asm/smp.h
> > @@ -69,9 +69,11 @@ extern int __cpu_logical_map[NR_CPUS];
> >   #define ACTION_BOOT_CPU     0
> >   #define ACTION_RESCHEDULE   1
> >   #define ACTION_CALL_FUNCTION        2
> > +#define ACTION_IRQ_WORK              3
> >   #define SMP_BOOT_CPU                BIT(ACTION_BOOT_CPU)
> >   #define SMP_RESCHEDULE              BIT(ACTION_RESCHEDULE)
> >   #define SMP_CALL_FUNCTION   BIT(ACTION_CALL_FUNCTION)
> > +#define SMP_IRQ_WORK         BIT(ACTION_IRQ_WORK)
> >
> >   struct secondary_data {
> >       unsigned long stack;
> > diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
> > index 1633ed4f692f..4272d2447445 100644
> > --- a/arch/loongarch/kernel/paravirt.c
> > +++ b/arch/loongarch/kernel/paravirt.c
> > @@ -2,6 +2,7 @@
> >   #include <linux/export.h>
> >   #include <linux/types.h>
> >   #include <linux/interrupt.h>
> > +#include <linux/irq_work.h>
> >   #include <linux/jump_label.h>
> >   #include <linux/kvm_para.h>
> >   #include <linux/static_call.h>
> > @@ -97,6 +98,11 @@ static irqreturn_t pv_ipi_interrupt(int irq, void *dev)
> >               info->ipi_irqs[IPI_CALL_FUNCTION]++;
> >       }
> >
> > +     if (action & SMP_IRQ_WORK) {
> > +             irq_work_run();
> > +             info->ipi_irqs[IPI_IRQ_WORK]++;
> > +     }
> > +
> Would you mind adding common api so that pv ipi handler and hw ipi
> handler can call it both? The coming avec MSI interrupt driver has the
> same requirement for ipi.
We can refactor it after AVEC upstream, if needed.

Huacai

>
> void do_ipi_demux(unsigned int action)
> {
>          irq_cpustat_t *info;
>
>          info = this_cpu_ptr(&irq_stat);
>          if (action & SMP_RESCHEDULE) {
>                  scheduler_ipi();
>                  info->ipi_irqs[IPI_RESCHEDULE]++;
>          }
>
>          if (action & SMP_CALL_FUNCTION) {
>                  generic_smp_call_function_interrupt();
>                  info->ipi_irqs[IPI_CALL_FUNCTION]++;
>          }
>
>         if (action & SMP_IRQ_WORK) {
>                 irq_work_run();
>                 info->ipi_irqs[IPI_IRQ_WORK]++;
> }
>
> Regards
> Bibo Mao
> >       return IRQ_HANDLED;
> >   }
> >
> > diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
> > index 0dfe2388ef41..7366de776f6e 100644
> > --- a/arch/loongarch/kernel/smp.c
> > +++ b/arch/loongarch/kernel/smp.c
> > @@ -13,6 +13,7 @@
> >   #include <linux/cpumask.h>
> >   #include <linux/init.h>
> >   #include <linux/interrupt.h>
> > +#include <linux/irq_work.h>
> >   #include <linux/profile.h>
> >   #include <linux/seq_file.h>
> >   #include <linux/smp.h>
> > @@ -70,6 +71,7 @@ static DEFINE_PER_CPU(int, cpu_state);
> >   static const char *ipi_types[NR_IPI] __tracepoint_string = {
> >       [IPI_RESCHEDULE] = "Rescheduling interrupts",
> >       [IPI_CALL_FUNCTION] = "Function call interrupts",
> > +     [IPI_IRQ_WORK] = "IRQ work interrupts",
> >   };
> >
> >   void show_ipi_list(struct seq_file *p, int prec)
> > @@ -217,6 +219,13 @@ void arch_smp_send_reschedule(int cpu)
> >   }
> >   EXPORT_SYMBOL_GPL(arch_smp_send_reschedule);
> >
> > +#ifdef CONFIG_IRQ_WORK
> > +void arch_irq_work_raise(void)
> > +{
> > +     mp_ops.send_ipi_single(smp_processor_id(), ACTION_IRQ_WORK);
> > +}
> > +#endif
> > +
> >   static irqreturn_t loongson_ipi_interrupt(int irq, void *dev)
> >   {
> >       unsigned int action;
> > @@ -234,6 +243,11 @@ static irqreturn_t loongson_ipi_interrupt(int irq, void *dev)
> >               per_cpu(irq_stat, cpu).ipi_irqs[IPI_CALL_FUNCTION]++;
> >       }
> >
> > +     if (action & SMP_IRQ_WORK) {
> > +             irq_work_run();
> > +             per_cpu(irq_stat, cpu).ipi_irqs[IPI_IRQ_WORK]++;
> > +     }
> > +
> >       return IRQ_HANDLED;
> >   }
> >
> >
>
>