| Message ID | 20220707110511.52129-3-zhengqi.arch@bytedance.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: run softirqs on the per-CPU IRQ stack | expand |
On Thu, Jul 7, 2022 at 1:05 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: > > Since softirqs are handled on the per-CPU IRQ stack, > let's support HAVE_IRQ_EXIT_ON_IRQ_STACK which causes > the core code to invoke __do_softirq() directly without > going through do_softirq_own_stack(). > > Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> I think the idea is right, but the extra function pointer adds more complexity than necessary: > static __always_inline void __el1_irq(struct pt_regs *regs, > void (*handler)(struct pt_regs *)) > { > enter_from_kernel_mode(regs); > > - irq_enter_rcu(); > - do_interrupt_handler(regs, handler); > - irq_exit_rcu(); > + do_interrupt_handler(regs, handler, irq_handler); > > arm64_preempt_schedule_irq(); > > @@ -699,9 +711,7 @@ static void noinstr el0_interrupt(struct pt_regs *regs, > if (regs->pc & BIT(55)) > arm64_apply_bp_hardening(); > > - irq_enter_rcu(); > - do_interrupt_handler(regs, handler); > - irq_exit_rcu(); > + do_interrupt_handler(regs, handler, irq_handler); > > exit_to_user_mode(regs); > } Would it be possible to instead pull out the call_on_irq_stack() so these two functions are instead called on the IRQ stack already? Arnd
On 2022/7/7 20:49, Arnd Bergmann wrote: > On Thu, Jul 7, 2022 at 1:05 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: >> >> Since softirqs are handled on the per-CPU IRQ stack, >> let's support HAVE_IRQ_EXIT_ON_IRQ_STACK which causes >> the core code to invoke __do_softirq() directly without >> going through do_softirq_own_stack(). >> >> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> > > I think the idea is right, but the extra function pointer adds more complexity > than necessary: > >> static __always_inline void __el1_irq(struct pt_regs *regs, >> void (*handler)(struct pt_regs *)) >> { >> enter_from_kernel_mode(regs); >> >> - irq_enter_rcu(); >> - do_interrupt_handler(regs, handler); >> - irq_exit_rcu(); >> + do_interrupt_handler(regs, handler, irq_handler); >> >> arm64_preempt_schedule_irq(); >> >> @@ -699,9 +711,7 @@ static void noinstr el0_interrupt(struct pt_regs *regs, >> if (regs->pc & BIT(55)) >> arm64_apply_bp_hardening(); >> >> - irq_enter_rcu(); >> - do_interrupt_handler(regs, handler); >> - irq_exit_rcu(); >> + do_interrupt_handler(regs, handler, irq_handler); >> >> exit_to_user_mode(regs); >> } > > Would it be possible to instead pull out the call_on_irq_stack() so these > two functions are instead called on the IRQ stack already? Hi, Do you mean to modify call_on_irq_stack()? I have tried doing a conditional jump inside call_on_irq_stack() like this: --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -888,13 +888,22 @@ SYM_FUNC_START(call_on_irq_stack) /* Move to the new stack and call the function there */ mov sp, x16 - blr x1 + + cmp x2, #1 + b.eq 99f + + blr x1 + b 999f + +99: bl irq_enter_rcu + blr x1 + bl irq_exit_rcu /* * Restore the SP from the FP, and restore the FP and LR from the frame * record. */ - mov sp, x29 +999: mov sp, x29 ldp x29, x30, [sp], #16 #ifdef CONFIG_SHADOW_CALL_STACK ldp scs_sp, xzr, [sp], #16 But this also requires a new parameter in do_interrupt_handler. I also considered implementing call_on_irq_stack() for nmi and irq separately, but later think it's unnecessary. > > Arnd Thanks, Qi
On Thu, Jul 7, 2022 at 3:38 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: > On 2022/7/7 20:49, Arnd Bergmann wrote: > > On Thu, Jul 7, 2022 at 1:05 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: > * Restore the SP from the FP, and restore the FP and LR from > the frame > * record. > */ > - mov sp, x29 > +999: mov sp, x29 > ldp x29, x30, [sp], #16 > #ifdef CONFIG_SHADOW_CALL_STACK > ldp scs_sp, xzr, [sp], #16 > > But this also requires a new parameter in do_interrupt_handler. > > I also considered implementing call_on_irq_stack() for nmi and irq > separately, but later think it's unnecessary. What I had in mind was something along the lines of diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index 56cefd33eb8e..432042b91588 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -270,10 +270,7 @@ static void do_interrupt_handler(struct pt_regs *regs, { struct pt_regs *old_regs = set_irq_regs(regs); - if (on_thread_stack()) - call_on_irq_stack(regs, handler); - else - handler(regs); + handler(regs); set_irq_regs(old_regs); } @@ -473,16 +470,31 @@ static void noinstr el1_interrupt(struct pt_regs *regs, __el1_irq(regs, handler); } -asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs) +static void noinstr el1_irq(struct pt_regs *regs) { el1_interrupt(regs, handle_arch_irq); } -asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs) +asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs) +{ + if (on_thread_stack()) + call_on_irq_stack(regs, el1_irq); + else + el1_irq(regs); +} + +static void noinstr el1_fiq(struct pt_regs *regs) { el1_interrupt(regs, handle_arch_fiq); } +asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs) +{ + if (on_thread_stack()) + call_on_irq_stack(regs, el1_fiq); + else + el1_fiq(regs); +} + asmlinkage void noinstr el1h_64_error_handler(struct pt_regs *regs) { unsigned long esr = read_sysreg(esr_el1); @@ -713,7 +731,7 @@ static void noinstr __el0_irq_handler_common(struct pt_regs *regs) asmlinkage void noinstr el0t_64_irq_handler(struct pt_regs *regs) { - __el0_irq_handler_common(regs); + call_on_irq_stack(regs, __el0_irq_handler_common); } static void noinstr __el0_fiq_handler_common(struct pt_regs *regs) @@ -723,7 +741,7 @@ static void noinstr __el0_fiq_handler_common(struct pt_regs *regs) asmlinkage void noinstr el0t_64_fiq_handler(struct pt_regs *regs) { - __el0_fiq_handler_common(regs); + call_on_irq_stack(regs, __el0_fiq_handler_common); } static void noinstr __el0_error_handler_common(struct pt_regs *regs) @@ -807,12 +825,12 @@ asmlinkage void noinstr el0t_32_sync_handler(struct pt_regs *regs) asmlinkage void noinstr el0t_32_irq_handler(struct pt_regs *regs) { - __el0_irq_handler_common(regs); + call_on_irq_stack(regs, __el0_irq_handler_common); } asmlinkage void noinstr el0t_32_fiq_handler(struct pt_regs *regs) { - __el0_fiq_handler_common(regs); + call_on_irq_stack(regs, __el0_fiq_handler_common); } asmlinkage void noinstr el0t_32_error_handler(struct pt_regs *regs) Not sure if that works. Arnd
On 2022/7/7 22:41, Arnd Bergmann wrote: > On Thu, Jul 7, 2022 at 3:38 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: >> On 2022/7/7 20:49, Arnd Bergmann wrote: >>> On Thu, Jul 7, 2022 at 1:05 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: >> * Restore the SP from the FP, and restore the FP and LR from >> the frame >> * record. >> */ >> - mov sp, x29 >> +999: mov sp, x29 >> ldp x29, x30, [sp], #16 >> #ifdef CONFIG_SHADOW_CALL_STACK >> ldp scs_sp, xzr, [sp], #16 >> >> But this also requires a new parameter in do_interrupt_handler. >> >> I also considered implementing call_on_irq_stack() for nmi and irq >> separately, but later think it's unnecessary. > > What I had in mind was something along the lines of > > diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c > index 56cefd33eb8e..432042b91588 100644 > --- a/arch/arm64/kernel/entry-common.c > +++ b/arch/arm64/kernel/entry-common.c > @@ -270,10 +270,7 @@ static void do_interrupt_handler(struct pt_regs *regs, > { > struct pt_regs *old_regs = set_irq_regs(regs); > > - if (on_thread_stack()) > - call_on_irq_stack(regs, handler); > - else > - handler(regs); > + handler(regs); > > set_irq_regs(old_regs); > } > @@ -473,16 +470,31 @@ static void noinstr el1_interrupt(struct pt_regs *regs, > __el1_irq(regs, handler); > } > > -asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs) > +static void noinstr el1_irq(struct pt_regs *regs) > { > el1_interrupt(regs, handle_arch_irq); > } > > -asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs) > +asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs) > +{ > + if (on_thread_stack()) > + call_on_irq_stack(regs, el1_irq); IMO, this can't work. Because el1_interrupt() will invoke arm64_preempt_schedule_irq(), which will cause scheduling on the IRQ stack. Thanks, Qi > + else > + el1_irq(regs); > +} > + > +static void noinstr el1_fiq(struct pt_regs *regs) > { > el1_interrupt(regs, handle_arch_fiq); > } > > +asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs) > +{ > + if (on_thread_stack()) > + call_on_irq_stack(regs, el1_fiq); > + else > + el1_fiq(regs); > +} > + > asmlinkage void noinstr el1h_64_error_handler(struct pt_regs *regs) > { > unsigned long esr = read_sysreg(esr_el1); > @@ -713,7 +731,7 @@ static void noinstr > __el0_irq_handler_common(struct pt_regs *regs) > > asmlinkage void noinstr el0t_64_irq_handler(struct pt_regs *regs) > { > - __el0_irq_handler_common(regs); > + call_on_irq_stack(regs, __el0_irq_handler_common); > } > > static void noinstr __el0_fiq_handler_common(struct pt_regs *regs) > @@ -723,7 +741,7 @@ static void noinstr > __el0_fiq_handler_common(struct pt_regs *regs) > > asmlinkage void noinstr el0t_64_fiq_handler(struct pt_regs *regs) > { > - __el0_fiq_handler_common(regs); > + call_on_irq_stack(regs, __el0_fiq_handler_common); > } > > static void noinstr __el0_error_handler_common(struct pt_regs *regs) > @@ -807,12 +825,12 @@ asmlinkage void noinstr > el0t_32_sync_handler(struct pt_regs *regs) > > asmlinkage void noinstr el0t_32_irq_handler(struct pt_regs *regs) > { > - __el0_irq_handler_common(regs); > + call_on_irq_stack(regs, __el0_irq_handler_common); > } > > asmlinkage void noinstr el0t_32_fiq_handler(struct pt_regs *regs) > { > - __el0_fiq_handler_common(regs); > + call_on_irq_stack(regs, __el0_fiq_handler_common); > } > > asmlinkage void noinstr el0t_32_error_handler(struct pt_regs *regs) > > Not sure if that works. > > Arnd
On Thu, Jul 7, 2022 at 5:00 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: > On 2022/7/7 22:41, Arnd Bergmann wrote: > > On Thu, Jul 7, 2022 at 3:38 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: > >> On 2022/7/7 20:49, Arnd Bergmann wrote: > > > > -asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs) > > +asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs) > > +{ > > + if (on_thread_stack()) > > + call_on_irq_stack(regs, el1_irq); > > IMO, this can't work. Because el1_interrupt() will invoke > arm64_preempt_schedule_irq(), which will cause scheduling on the > IRQ stack. Ah, too bad. I spent some more time looking for a simpler approach, but couldn't find one I'm happy with. One idea might be to have callback functions for each combinations of irq/fiq with irq/pnmi to avoid the nested callback pointers. Not sure if that helps. Arnd
On 2022/7/8 04:55, Arnd Bergmann wrote: > On Thu, Jul 7, 2022 at 5:00 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: >> On 2022/7/7 22:41, Arnd Bergmann wrote: >>> On Thu, Jul 7, 2022 at 3:38 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: >>>> On 2022/7/7 20:49, Arnd Bergmann wrote: >>> >>> -asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs) >>> +asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs) >>> +{ >>> + if (on_thread_stack()) >>> + call_on_irq_stack(regs, el1_irq); >> >> IMO, this can't work. Because el1_interrupt() will invoke >> arm64_preempt_schedule_irq(), which will cause scheduling on the >> IRQ stack. > > Ah, too bad. I spent some more time looking for a simpler approach, > but couldn't find one I'm happy with. One idea might be to have > callback functions for each combinations of irq/fiq with irq/pnmi > to avoid the nested callback pointers. Not sure if that helps. Maybe nested callback pointers are not always a wild beast. ;) This method does not change much, and we can also conveniently stuff all kinds of things in do_handler() that we want to run on the IRQ stack in addition to the handler(). Thanks, Qi > > Arnd
On Fri, Jul 8, 2022 at 5:13 AM Qi Zheng <zhengqi.arch@bytedance.com> wrote: > On 2022/7/8 04:55, Arnd Bergmann wrote: > > On Thu, Jul 7, 2022 at 5:00 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: > >> On 2022/7/7 22:41, Arnd Bergmann wrote: > >>> On Thu, Jul 7, 2022 at 3:38 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: > >>>> On 2022/7/7 20:49, Arnd Bergmann wrote: > >>> > >>> -asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs) > >>> +asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs) > >>> +{ > >>> + if (on_thread_stack()) > >>> + call_on_irq_stack(regs, el1_irq); > >> > >> IMO, this can't work. Because el1_interrupt() will invoke > >> arm64_preempt_schedule_irq(), which will cause scheduling on the > >> IRQ stack. > > > > Ah, too bad. I spent some more time looking for a simpler approach, > > but couldn't find one I'm happy with. One idea might be to have > > callback functions for each combinations of irq/fiq with irq/pnmi > > to avoid the nested callback pointers. Not sure if that helps. > > Maybe nested callback pointers are not always a wild beast. ;) > This method does not change much, and we can also conveniently stuff > all kinds of things in do_handler() that we want to run on the IRQ > stack in addition to the handler(). Right, your approach is probably the one that changes the existing code the least. I see that x86 handles this by having call_on_irq_stack() in an inline asm, but this in turn complicates the asm implementation, which is also worth keeping simple. Arnd
On 2022/7/8 16:52, Arnd Bergmann wrote: > On Fri, Jul 8, 2022 at 5:13 AM Qi Zheng <zhengqi.arch@bytedance.com> wrote: >> On 2022/7/8 04:55, Arnd Bergmann wrote: >>> On Thu, Jul 7, 2022 at 5:00 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: >>>> On 2022/7/7 22:41, Arnd Bergmann wrote: >>>>> On Thu, Jul 7, 2022 at 3:38 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote: >>>>>> On 2022/7/7 20:49, Arnd Bergmann wrote: >>>>> >>>>> -asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs) >>>>> +asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs) >>>>> +{ >>>>> + if (on_thread_stack()) >>>>> + call_on_irq_stack(regs, el1_irq); >>>> >>>> IMO, this can't work. Because el1_interrupt() will invoke >>>> arm64_preempt_schedule_irq(), which will cause scheduling on the >>>> IRQ stack. >>> >>> Ah, too bad. I spent some more time looking for a simpler approach, >>> but couldn't find one I'm happy with. One idea might be to have >>> callback functions for each combinations of irq/fiq with irq/pnmi >>> to avoid the nested callback pointers. Not sure if that helps. >> >> Maybe nested callback pointers are not always a wild beast. ;) >> This method does not change much, and we can also conveniently stuff >> all kinds of things in do_handler() that we want to run on the IRQ >> stack in addition to the handler(). > > Right, your approach is probably the one that changes the existing > code the least. I see that x86 handles this by having call_on_irq_stack() > in an inline asm, but this in turn complicates the asm implementation, > which is also worth keeping simple. Yes, and I see that the commit f2c5092190f2 ("arch/*: Disable softirq stacks on PREEMPT_RT.") has been merged into next-20220707, so I will rebase to the next-20220707 and send the next version. Thank you very much :) > > Arnd
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 402e16fec02a..89f6368b705e 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -231,6 +231,7 @@ config ARM64 select TRACE_IRQFLAGS_SUPPORT select TRACE_IRQFLAGS_NMI_SUPPORT select HAVE_SOFTIRQ_ON_OWN_STACK + select HAVE_IRQ_EXIT_ON_IRQ_STACK help ARM 64-bit (AArch64) Linux support. diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h index d94aecff9690..8bff0aa7ab50 100644 --- a/arch/arm64/include/asm/exception.h +++ b/arch/arm64/include/asm/exception.h @@ -54,7 +54,9 @@ asmlinkage void el0t_32_fiq_handler(struct pt_regs *regs); asmlinkage void el0t_32_error_handler(struct pt_regs *regs); asmlinkage void call_on_irq_stack(struct pt_regs *regs, - void (*func)(struct pt_regs *)); + void (*func)(struct pt_regs *), + void (*do_func)(struct pt_regs *, + void (*)(struct pt_regs *))); asmlinkage void asm_exit_to_user_mode(struct pt_regs *regs); void do_mem_abort(unsigned long far, unsigned long esr, struct pt_regs *regs); diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index c75ca36b4a49..935d1ab150b5 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -266,14 +266,16 @@ static void __sched arm64_preempt_schedule_irq(void) } static void do_interrupt_handler(struct pt_regs *regs, - void (*handler)(struct pt_regs *)) + void (*handler)(struct pt_regs *), + void (*do_handler)(struct pt_regs *, + void (*)(struct pt_regs *))) { struct pt_regs *old_regs = set_irq_regs(regs); if (on_thread_stack()) - call_on_irq_stack(regs, handler); + call_on_irq_stack(regs, handler, do_handler); else - handler(regs); + do_handler(regs, handler); set_irq_regs(old_regs); } @@ -441,22 +443,32 @@ asmlinkage void noinstr el1h_64_sync_handler(struct pt_regs *regs) } } +static void nmi_handler(struct pt_regs *regs, void (*handler)(struct pt_regs *)) +{ + handler(regs); +} + static __always_inline void __el1_pnmi(struct pt_regs *regs, void (*handler)(struct pt_regs *)) { arm64_enter_nmi(regs); - do_interrupt_handler(regs, handler); + do_interrupt_handler(regs, handler, nmi_handler); arm64_exit_nmi(regs); } +static void irq_handler(struct pt_regs *regs, void (*handler)(struct pt_regs *)) +{ + irq_enter_rcu(); + handler(regs); + irq_exit_rcu(); +} + static __always_inline void __el1_irq(struct pt_regs *regs, void (*handler)(struct pt_regs *)) { enter_from_kernel_mode(regs); - irq_enter_rcu(); - do_interrupt_handler(regs, handler); - irq_exit_rcu(); + do_interrupt_handler(regs, handler, irq_handler); arm64_preempt_schedule_irq(); @@ -699,9 +711,7 @@ static void noinstr el0_interrupt(struct pt_regs *regs, if (regs->pc & BIT(55)) arm64_apply_bp_hardening(); - irq_enter_rcu(); - do_interrupt_handler(regs, handler); - irq_exit_rcu(); + do_interrupt_handler(regs, handler, irq_handler); exit_to_user_mode(regs); } diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 254fe31c03a0..1c351391f6bd 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -867,7 +867,9 @@ NOKPROBE(ret_from_fork) /* * void call_on_irq_stack(struct pt_regs *regs, - * void (*func)(struct pt_regs *)); + * void (*func)(struct pt_regs *) + * void (*do_func)(struct pt_regs *, + * void (*)(struct pt_regs *))); * * Calls func(regs) using this CPU's irq stack and shadow irq stack. */ @@ -886,7 +888,7 @@ SYM_FUNC_START(call_on_irq_stack) /* Move to the new stack and call the function there */ mov sp, x16 - blr x1 + blr x2 /* * Restore the SP from the FP, and restore the FP and LR from the frame diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c index e6aa37672fd4..54cd418d47ef 100644 --- a/arch/arm64/kernel/irq.c +++ b/arch/arm64/kernel/irq.c @@ -72,14 +72,15 @@ static void init_irq_stacks(void) } #endif -static void ____do_softirq(struct pt_regs *regs) +static void ____do_softirq(struct pt_regs *regs, + void (*handler)(struct pt_regs *)) { __do_softirq(); } void do_softirq_own_stack(void) { - call_on_irq_stack(NULL, ____do_softirq); + call_on_irq_stack(NULL, NULL, ____do_softirq); } static void default_handle_irq(struct pt_regs *regs)
Since softirqs are handled on the per-CPU IRQ stack, let's support HAVE_IRQ_EXIT_ON_IRQ_STACK which causes the core code to invoke __do_softirq() directly without going through do_softirq_own_stack(). Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/exception.h | 4 +++- arch/arm64/kernel/entry-common.c | 30 ++++++++++++++++++++---------- arch/arm64/kernel/entry.S | 6 ++++-- arch/arm64/kernel/irq.c | 5 +++-- 5 files changed, 31 insertions(+), 15 deletions(-)