From: Qi Zheng <zhengqi.arch@bytedance.com> To: Arnd Bergmann <arnd@arndb.de> Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org> Subject: Re: [RFC PATCH 2/2] arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK Date: Thu, 7 Jul 2022 21:38:20 +0800 [thread overview] Message-ID: <42bfd82c-b3fb-c942-d6f2-ae5adec90a26@bytedance.com> (raw) In-Reply-To: <CAK8P3a1-rL391dp33D5r+SgQ+L0u7Neta_-DZoZL=+c1zPtNQg@mail.gmail.com> 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
WARNING: multiple messages have this Message-ID (diff)
From: Qi Zheng <zhengqi.arch@bytedance.com> To: Arnd Bergmann <arnd@arndb.de> Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org> Subject: Re: [RFC PATCH 2/2] arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK Date: Thu, 7 Jul 2022 21:38:20 +0800 [thread overview] Message-ID: <42bfd82c-b3fb-c942-d6f2-ae5adec90a26@bytedance.com> (raw) In-Reply-To: <CAK8P3a1-rL391dp33D5r+SgQ+L0u7Neta_-DZoZL=+c1zPtNQg@mail.gmail.com> 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-07-07 13:38 UTC|newest] Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-07-07 11:05 [RFC PATCH 0/2] arm64: run softirqs on the per-CPU IRQ stack Qi Zheng 2022-07-07 11:05 ` Qi Zheng 2022-07-07 11:05 ` [RFC PATCH 1/2] " Qi Zheng 2022-07-07 11:05 ` Qi Zheng 2022-07-07 12:58 ` Arnd Bergmann 2022-07-07 12:58 ` Arnd Bergmann 2022-07-07 13:43 ` Qi Zheng 2022-07-07 13:43 ` Qi Zheng 2022-07-07 13:53 ` Arnd Bergmann 2022-07-07 13:53 ` Arnd Bergmann 2022-07-07 15:05 ` Qi Zheng 2022-07-07 15:05 ` Qi Zheng 2022-07-08 2:56 ` kernel test robot 2022-07-07 11:05 ` [RFC PATCH 2/2] arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK Qi Zheng 2022-07-07 11:05 ` Qi Zheng 2022-07-07 12:49 ` Arnd Bergmann 2022-07-07 12:49 ` Arnd Bergmann 2022-07-07 13:38 ` Qi Zheng [this message] 2022-07-07 13:38 ` Qi Zheng 2022-07-07 14:41 ` Arnd Bergmann 2022-07-07 14:41 ` Arnd Bergmann 2022-07-07 15:00 ` Qi Zheng 2022-07-07 15:00 ` Qi Zheng 2022-07-07 20:55 ` Arnd Bergmann 2022-07-07 20:55 ` Arnd Bergmann 2022-07-08 3:13 ` Qi Zheng 2022-07-08 3:13 ` Qi Zheng 2022-07-08 8:52 ` Arnd Bergmann 2022-07-08 8:52 ` Arnd Bergmann 2022-07-08 9:13 ` Qi Zheng 2022-07-08 9:13 ` Qi Zheng
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