From d275fbb11ee994db5f532f6dfa139fc6d1d328f9 Mon Sep 17 00:00:00 2001
From: Julien Thierry <julien.thierry@arm.com>
Date: Wed, 13 Feb 2019 19:53:29 +0800
Subject: [PATCH] irqchip/gic-v3: Remove acknowledge loop

mainline inclusion
from mainline-v4.20-rc1
commit 342677d70ab92142b483fc68bcade74cdf969785
category: bugfix
bugzilla: 9291
CVE: NA

--------------------------------

Multiple interrupts pending for a CPU is actually rare. Doing an
acknowledge loop does not give much better performance or even can
deteriorate them.

Do not loop when an interrupt has been acknowledged, just return
from interrupt and wait for another one to be raised.

Tested-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Wei Li <liwei391@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 drivers/irqchip/irq-gic-v3.c | 65 +++++++++++++++++-------------------
 1 file changed, 31 insertions(+), 34 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 6232f98ef81b..8f87f40c9460 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -348,48 +348,45 @@ static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs
 {
 	u32 irqnr;
 
-	do {
-		irqnr = gic_read_iar();
+	irqnr = gic_read_iar();
 
-		if (likely(irqnr > 15 && irqnr < 1020) || irqnr >= 8192) {
-			int err;
+	if (likely(irqnr > 15 && irqnr < 1020) || irqnr >= 8192) {
+		int err;
 
-			if (static_branch_likely(&supports_deactivate_key))
+		if (static_branch_likely(&supports_deactivate_key))
+			gic_write_eoir(irqnr);
+		else
+			isb();
+
+		err = handle_domain_irq(gic_data.domain, irqnr, regs);
+		if (err) {
+			WARN_ONCE(true, "Unexpected interrupt received!\n");
+			if (static_branch_likely(&supports_deactivate_key)) {
+				if (irqnr < 8192)
+					gic_write_dir(irqnr);
+			} else {
 				gic_write_eoir(irqnr);
-			else
-				isb();
-
-			err = handle_domain_irq(gic_data.domain, irqnr, regs);
-			if (err) {
-				WARN_ONCE(true, "Unexpected interrupt received!\n");
-				if (static_branch_likely(&supports_deactivate_key)) {
-					if (irqnr < 8192)
-						gic_write_dir(irqnr);
-				} else {
-					gic_write_eoir(irqnr);
-				}
 			}
-			continue;
 		}
-		if (irqnr < 16) {
-			gic_write_eoir(irqnr);
-			if (static_branch_likely(&supports_deactivate_key))
-				gic_write_dir(irqnr);
+		return;
+	}
+	if (irqnr < 16) {
+		gic_write_eoir(irqnr);
+		if (static_branch_likely(&supports_deactivate_key))
+			gic_write_dir(irqnr);
 #ifdef CONFIG_SMP
-			/*
-			 * Unlike GICv2, we don't need an smp_rmb() here.
-			 * The control dependency from gic_read_iar to
-			 * the ISB in gic_write_eoir is enough to ensure
-			 * that any shared data read by handle_IPI will
-			 * be read after the ACK.
-			 */
-			handle_IPI(irqnr, regs);
+		/*
+		 * Unlike GICv2, we don't need an smp_rmb() here.
+		 * The control dependency from gic_read_iar to
+		 * the ISB in gic_write_eoir is enough to ensure
+		 * that any shared data read by handle_IPI will
+		 * be read after the ACK.
+		 */
+		handle_IPI(irqnr, regs);
 #else
-			WARN_ONCE(true, "Unexpected SGI received!\n");
+		WARN_ONCE(true, "Unexpected SGI received!\n");
 #endif
-			continue;
-		}
-	} while (irqnr != ICC_IAR1_EL1_SPURIOUS);
+	}
 }
 
 static void __init gic_dist_init(void)
-- 
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