Re: [PATCHv3 2/3] arm64: entry: refactor EL1 interrupt entry logic

On Fri, Oct 01, 2021 at 10:21:06AM +0100, Marc Zyngier wrote:

On Thu, 30 Sep 2021 14:17:07 +0100,
Pingfan Liu [off-list ref] wrote:

quoted

From: Mark Rutland <mark.rutland@arm.com>

Currently we distinguish IRQ and definitely-PNMI at entry/exit time
via the enter_el1_irq_or_nmi() and enter_el1_irq_or_nmi() helpers. In
subsequent patches we'll need to handle the two cases more distinctly
in the body of the exception handler.

To make this possible, this patch refactors el1_interrupt to be a
top-level dispatcher to separate handlers for the IRQ and PNMI cases,
removing the need for the enter_el1_irq_or_nmi() and
exit_el1_irq_or_nmi() helpers.

Note that since arm64_enter_nmi() calls __nmi_enter(), which
increments the preemt_count, we could never preempt when handling a
PNMI. We now only check for preemption in the IRQ case, which makes
this clearer.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Julien Thierry <redacted>
Cc: Thomas Gleixner <redacted>
Cc: Yuichi Ito <redacted>
Cc: Pingfan Liu <redacted>
Cc: linux-kernel@vger.kernel.org
To: linux-arm-kernel@lists.infradead.org
---
 arch/arm64/kernel/entry-common.c | 44 ++++++++++++++++----------------
 1 file changed, 22 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 32f9796c4ffe..5f1473319fb0 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c

@@ -219,22 +219,6 @@ 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();

@@ -432,14 +416,19 @@ 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);
-
-	enter_el1_irq_or_nmi(regs);
+	arm64_enter_nmi(regs);
 	do_interrupt_handler(regs, handler);
+	arm64_exit_nmi(regs);
+}
 
+static __always_inline void
+__el1_interrupt(struct pt_regs *regs, void (*handler)(struct pt_regs *))
+{
+	enter_from_kernel_mode(regs);
+	do_interrupt_handler(regs, handler);
 	/*
 	 * Note: thread_info::preempt_count includes both thread_info::count
 	 * and thread_info::need_resched, and is not equivalent to

@@ -448,8 +437,19 @@ static void noinstr el1_interrupt(struct pt_regs *regs,
 	if (IS_ENABLED(CONFIG_PREEMPTION) &&
 	    READ_ONCE(current_thread_info()->preempt_count) == 0)
 		arm64_preempt_schedule_irq();
+	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_interrupt(regs, handler);
 
-	exit_el1_irq_or_nmi(regs);

nit: spurious blank line.

OK, I will fix it.

quoted

 }
 
 asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs)

With Mark's remark addressed,

Reviewed-by: Marc Zyngier <maz@kernel.org>

Thanks,

	Pingfan

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