Re: [PATCH -next V10 09/10] riscv: stack: Support HAVE_SOFTIRQ_ON_OWN_STACK

[Guo Ren]

On Thu, Dec 8, 2022 at 6:12 PM Björn Töpel <bjorn@xxxxxxxxxx> wrote:
>
> guoren@xxxxxxxxxx writes:
>
> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> >
> > Add the HAVE_SOFTIRQ_ON_OWN_STACK feature for the IRQ_STACKS config. The
> > irq and softirq use the same independent irq_stack of percpu by time
> > division multiplexing.
> >
> > Tested-by: Jisheng Zhang <jszhang@xxxxxxxxxx>
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
> > ---
> >  arch/riscv/Kconfig      |  7 ++++---
> >  arch/riscv/kernel/irq.c | 33 +++++++++++++++++++++++++++++++++
> >  2 files changed, 37 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 0a9d4bdc0338..bd4c4ae4cdc9 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -447,12 +447,13 @@ config FPU
> >         If you don't know what to do here, say Y.
> >
> >  config IRQ_STACKS
> > -     bool "Independent irq stacks" if EXPERT
> > +     bool "Independent irq & softirq stacks" if EXPERT
> >       default y
> >       select HAVE_IRQ_EXIT_ON_IRQ_STACK
> > +     select HAVE_SOFTIRQ_ON_OWN_STACK
>
> HAVE_IRQ_EXIT_ON_IRQ_STACK is used by softirq.c Shouldn't that be
> selected introduced in this patch, instead of the previous one?
This patch depends on the previous one. And the previous one could
work separately.

>
> >       help
> > -       Add independent irq stacks for percpu to prevent kernel stack overflows.
> > -       We may save some memory footprint by disabling IRQ_STACKS.
> > +       Add independent irq & softirq stacks for percpu to prevent kernel stack
> > +       overflows. We may save some memory footprint by disabling IRQ_STACKS.
>
> Same comment from previous patch. Please use the same wording/config as
> other archs.
>
> >  endmenu # "Platform type"
> >
> > diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
> > index 5d77f692b198..a6406da34937 100644
> > --- a/arch/riscv/kernel/irq.c
> > +++ b/arch/riscv/kernel/irq.c
> > @@ -11,6 +11,7 @@
> >  #include <linux/seq_file.h>
> >  #include <asm/smp.h>
> >  #include <asm/vmap_stack.h>
> > +#include <asm/softirq_stack.h>
> >
> >  #ifdef CONFIG_IRQ_STACKS
> >  static DEFINE_PER_CPU(ulong *, irq_stack_ptr);
> > @@ -38,6 +39,38 @@ static void init_irq_stacks(void)
> >               per_cpu(irq_stack_ptr, cpu) = per_cpu(irq_stack, cpu);
> >  }
> >  #endif /* CONFIG_VMAP_STACK */
> > +
> > +#ifdef CONFIG_HAVE_SOFTIRQ_ON_OWN_STACK
> > +void do_softirq_own_stack(void)
> > +{
> > +#ifdef CONFIG_IRQ_STACKS
> > +     if (on_thread_stack()) {
> > +             ulong *sp = per_cpu(irq_stack_ptr, smp_processor_id())
> > +                                     + IRQ_STACK_SIZE/sizeof(ulong);
> > +             __asm__ __volatile(
> > +             "addi   sp, sp, -"RISCV_SZPTR  "\n"
> > +             REG_S"  ra, (sp)                \n"
> > +             "addi   sp, sp, -"RISCV_SZPTR  "\n"
> > +             REG_S"  s0, (sp)                \n"
> > +             "addi   s0, sp, 2*"RISCV_SZPTR "\n"
> > +             "move   sp, %[sp]               \n"
> > +             "call   __do_softirq            \n"
> > +             "addi   sp, s0, -2*"RISCV_SZPTR"\n"
> > +             REG_L"  s0, (sp)                \n"
> > +             "addi   sp, sp, "RISCV_SZPTR   "\n"
> > +             REG_L"  ra, (sp)                \n"
> > +             "addi   sp, sp, "RISCV_SZPTR   "\n"
> > +             :
> > +             : [sp] "r" (sp)
> > +             : "a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7",
> > +               "t0", "t1", "t2", "t3", "t4", "t5", "t6",
> > +               "memory");
>
> Same as previous patch. Please avoid C&P and have a look at how
> call_on_stack is done on x86.
Okay.

>
>
> Björn



-- 
Best Regards
 Guo Ren