linux-kernel - [PATCH v2 3/4] arm64: smp: Setup IPI_CALL_NMI

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Message-Id: <1589973115-14757-4-git-send-email-sumit.garg@linaro.org>
Date:   Wed, 20 May 2020 16:41:54 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, will@...nel.org, tglx@...utronix.de,
        jason@...edaemon.net, maz@...nel.org,
        julien.thierry.kdev@...il.com, dianders@...omium.org,
        daniel.thompson@...aro.org, jason.wessel@...driver.com,
        kgdb-bugreport@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        Sumit Garg <sumit.garg@...aro.org>
Subject: [PATCH v2 3/4] arm64: smp: Setup IPI_CALL_NMI_FUNC as a pseudo NMI

Setup IPI_CALL_NMI_FUNC as a pseudo NMI using generic interrupt framework
APIs. In case a plarform doesn't provide support for pseudo NMIs, switch
back to IPI_CALL_NMI_FUNC being a normal interrupt.

Signed-off-by: Sumit Garg <sumit.garg@...aro.org>
---
 arch/arm64/kernel/smp.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 236784e..c5e42a1 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -68,6 +68,7 @@ struct secondary_data secondary_data;
 int cpus_stuck_in_kernel;
 
 static int ipi_irq_base;
+static int ipi_nmi = -1;
 static int nr_ipi = NR_IPI;
 static struct irq_desc *ipi_desc[NR_IPI];
 
@@ -986,8 +987,14 @@ static void ipi_setup(int cpu)
 	if (ipi_irq_base) {
 		int i;
 
-		for (i = 0; i < nr_ipi; i++)
-			enable_percpu_irq(ipi_irq_base + i, 0);
+		for (i = 0; i < nr_ipi; i++) {
+			if (ipi_nmi == ipi_irq_base + i) {
+				if (!prepare_percpu_nmi(ipi_nmi))
+					enable_percpu_nmi(ipi_nmi, 0);
+			} else {
+				enable_percpu_irq(ipi_irq_base + i, 0);
+			}
+		}
 	}
 }
 
@@ -997,23 +1004,33 @@ static void ipi_teardown(int cpu)
 		int i;
 
 		for (i = 0; i < nr_ipi; i++)
-			disable_percpu_irq(ipi_irq_base + i);
+			if (ipi_nmi == ipi_irq_base + i) {
+				disable_percpu_nmi(ipi_nmi);
+				teardown_percpu_nmi(ipi_nmi);
+			} else {
+				disable_percpu_irq(ipi_irq_base + i);
+			}
 	}
 }
 
 void __init set_smp_ipi_range(int ipi_base, int n)
 {
-	int i;
+	int i, err;
 
 	WARN_ON(n < NR_IPI);
 	nr_ipi = min(n, NR_IPI);
 
-	for (i = 0; i < nr_ipi; i++) {
-		int err;
+	err = request_percpu_nmi(ipi_base + IPI_CALL_NMI_FUNC,
+				 ipi_handler, "IPI", &irq_stat);
+	if (!err)
+		ipi_nmi = ipi_base + IPI_CALL_NMI_FUNC;
 
-		err = request_percpu_irq(ipi_base + i, ipi_handler,
-					 "IPI", &irq_stat);
-		WARN_ON(err);
+	for (i = 0; i < nr_ipi; i++) {
+		if (ipi_base + i != ipi_nmi) {
+			err = request_percpu_irq(ipi_base + i, ipi_handler,
+						 "IPI", &irq_stat);
+			WARN_ON(err);
+		}
 
 		ipi_desc[i] = irq_to_desc(ipi_base + i);
 		irq_set_status_flags(ipi_base + i, IRQ_NO_ACCOUNTING);
-- 
2.7.4