[PATCHv2 5/5] irqchip/GICv3: make reschedule-ipi light weight

From: Pingfan Liu <kernelfans@gmail.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Pingfan Liu <kernelfans@gmail.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Marc Zyngier <maz@kernel.org>, Joey Gouly <joey.gouly@arm.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	Julien Thierry <julien.thierry@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Yuichi Ito <ito-yuichi@fujitsu.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCHv2 5/5] irqchip/GICv3: make reschedule-ipi light weight
Date: Fri, 24 Sep 2021 21:28:37 +0800	[thread overview]
Message-ID: <20210924132837.45994-6-kernelfans@gmail.com> (raw)
In-Reply-To: <20210924132837.45994-1-kernelfans@gmail.com>

To achieve the light weight as
DEFINE_IDTENTRY_SYSVEC_SIMPLE(sysvec_reschedule_ipi) on x86, it had
better treat irqnr differently at the frontend. And let IPI_RESCHEDULE
call __irq_enter_raw() instead of irq_enter_rcu().

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Julien Thierry <julien.thierry@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yuichi Ito <ito-yuichi@fujitsu.com>
Cc: linux-kernel@vger.kernel.org
To: linux-arm-kernel@lists.infradead.org
---
 drivers/irqchip/irq-gic-v3.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 906538fa8771..593d4539a209 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -709,6 +709,9 @@ static void gic_handle_nmi(struct pt_regs *regs)
 		gic_deactivate_unhandled(irqnr);
 }
 
+/* RESCHEDULE IPI hwirq nr is 0, and the only raw one */
+static unsigned long raw_interrupt_mask = 1;
+
 static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
 {
 	u32 irqnr;
@@ -729,12 +732,20 @@ static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs
 	else
 		isb();
 
-	irq_enter_rcu();
+	if (raw_interrupt_mask & 1 << irqnr)
+		__irq_enter_raw();
+	else
+		irq_enter_rcu();
+
 	if (handle_domain_irq(gic_data.domain, irqnr, regs)) {
 		WARN_ONCE(true, "Unexpected interrupt received!\n");
 		gic_deactivate_unhandled(irqnr);
 	}
-	irq_exit_rcu();
+
+	if (raw_interrupt_mask & 1 << irqnr)
+		__irq_exit_raw();
+	else
+		irq_exit_rcu();
 }
 
 static u32 gic_get_pribits(void)
-- 
2.31.1

