Re: [PATCH 10/15] irq: arm64: perform irqentry in entry code

Pingfan Liu
2021-10-22T01:58:07Z

On Thu, Oct 21, 2021 at 07:02:31PM +0100, Mark Rutland wrote:
> In preparation for removing HANDLE_DOMAIN_IRQ_IRQENTRY, have arch/arm64
> perform all the irqentry accounting in its entry code.
>
> As arch/arm64 already performs portions of the irqentry logic in
> enter_from_kernel_mode() and exit_to_kernel_mode(), including
> rcu_irq_{enter,exit}(), the only additional calls that need to be made
> are to irq_{enter,exit}_rcu(). Removing the calls to
> rcu_irq_{enter,exit}() from handle_domain_irq() ensures that we inform
> RCU once per IRQ entry and will correctly identify quiescent periods.
>
> Since we should not call irq_{enter,exit}_rcu() when entering a
> pseudo-NMI, el1_interrupt() is reworked to have separate __el1_irq() and
> __el1_pnmi() paths for regular IRQ and psuedo-NMI entry, with
> irq_{enter,exit}_irq() only called for the former.
>
> In preparation for removing HANDLE_DOMAIN_IRQ, the irq regs are managed
> in do_interrupt_handler() for both regular IRQ and pseudo-NMI. This is
> currently redundant, but not harmful.
>
> For clarity the preemption logic is moved into __el1_irq(). We should
> never preempt within a pseudo-NMI, and arm64_enter_nmi() already
> enforces this by incrementing the preempt_count, but it's clearer if we
> never invoke the preemption logic when entering a pseudo-NMI.
>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Will Deacon <will@kernel.org>
> ---
> arch/arm64/Kconfig | 1 -
> arch/arm64/kernel/entry-common.c | 52 ++++++++++++++++++++++++----------------
> 2 files changed, 31 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 553239a5a5f7..5c7ae4c3954b 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -134,7 +134,6 @@ config ARM64
> select GENERIC_GETTIMEOFDAY
> select GENERIC_VDSO_TIME_NS
> select HANDLE_DOMAIN_IRQ
> - select HANDLE_DOMAIN_IRQ_IRQENTRY
> select HARDIRQS_SW_RESEND
> select HAVE_MOVE_PMD
> select HAVE_MOVE_PUD
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index 32f9796c4ffe..f7408edf8571 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -17,6 +17,7 @@
> #include <asm/daifflags.h>
> #include <asm/esr.h>
> #include <asm/exception.h>
> +#include <asm/irq_regs.h>
> #include <asm/kprobes.h>
> #include <asm/mmu.h>
> #include <asm/processor.h>
> @@ -219,22 +220,6 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
> lockdep_hardirqs_on(CALLER_ADDR0);
> }
>
> -static void noinstr enter_el1_irq_or_nmi(struct pt_regs *regs)
> -{
> - if (IS_ENABLED(CONFIG_ARM64_PSEUDO_NMI) && !interrupts_enabled(regs))
> - arm64_enter_nmi(regs);
> - else
> - enter_from_kernel_mode(regs);
> -}
> -
> -static void noinstr exit_el1_irq_or_nmi(struct pt_regs *regs)
> -{
> - if (IS_ENABLED(CONFIG_ARM64_PSEUDO_NMI) && !interrupts_enabled(regs))
> - arm64_exit_nmi(regs);
> - else
> - exit_to_kernel_mode(regs);
> -}
> -
> static void __sched arm64_preempt_schedule_irq(void)
> {
> lockdep_assert_irqs_disabled();
> @@ -263,10 +248,14 @@ static void __sched arm64_preempt_schedule_irq(void)
> static void do_interrupt_handler(struct pt_regs *regs,
> void (*handler)(struct pt_regs *))
> {
> + struct pt_regs *old_regs = set_irq_regs(regs);
> +
> if (on_thread_stack())
> call_on_irq_stack(regs, handler);
> else
> handler(regs);
> +
> + set_irq_regs(old_regs);
> }
>
> extern void (*handle_arch_irq)(struct pt_regs *);
> @@ -432,13 +421,22 @@ asmlinkage void noinstr el1h_64_sync_handler(struct pt_regs *regs)
> }
> }
>
> -static void noinstr el1_interrupt(struct pt_regs *regs,
> - void (*handler)(struct pt_regs *))
> +static __always_inline void __el1_pnmi(struct pt_regs *regs,
> + void (*handler)(struct pt_regs *))
> {
> - write_sysreg(DAIF_PROCCTX_NOIRQ, daif);
> + arm64_enter_nmi(regs);
> + do_interrupt_handler(regs, handler);
> + arm64_exit_nmi(regs);
> +}
> +
> +static __always_inline void __el1_irq(struct pt_regs *regs,
> + void (*handler)(struct pt_regs *))
> +{
> + enter_from_kernel_mode(regs);
>
> - enter_el1_irq_or_nmi(regs);
> + irq_enter_rcu();
> do_interrupt_handler(regs, handler);
> + irq_exit_rcu();
>
> /*
> * Note: thread_info::preempt_count includes both thread_info::count
> @@ -449,7 +447,17 @@ static void noinstr el1_interrupt(struct pt_regs *regs,
> READ_ONCE(current_thread_info()->preempt_count) == 0)
> arm64_preempt_schedule_irq();
>
> - exit_el1_irq_or_nmi(regs);
> + exit_to_kernel_mode(regs);
> +}
> +static void noinstr el1_interrupt(struct pt_regs *regs,
> + void (*handler)(struct pt_regs *))
> +{
> + write_sysreg(DAIF_PROCCTX_NOIRQ, daif);
> +
> + if (IS_ENABLED(CONFIG_ARM64_PSEUDO_NMI) && !interrupts_enabled(regs))
> + __el1_pnmi(regs, handler);
> + else
> + __el1_irq(regs, handler);
> }
>
> asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs)
> @@ -667,7 +675,9 @@ 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();
>
> exit_to_user_mode(regs);
> }

Reviewed-by: Pingfan Liu <kernelfans@gmail.com>