linux-kernel - [PATCH 2/2] misc: Register a PPI for the vcpu stall detection virtual device

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Date: Thu, 23 May 2024 16:04:13 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: arnd@...db.de, gregkh@...uxfoundation.org, will@...nel.org, maz@...nel.org, 
	Rob Herring <robh+dt@...nel.org>, Dragan Cvetic <dragan.cvetic@...inx.com>, 
	Guenter Roeck <linux@...ck-us.net>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	kernel-team@...roid.com, Sebastian Ene <sebastianene@...gle.com>
Subject: [PATCH 2/2] misc: Register a PPI for the vcpu stall detection virtual device

Request a PPI for each vCPU during probe which will be used by the host
to communicate a stall detected event on the vCPU. When the host raises
this interrupt from the virtual machine monitor, the guest is expected to
handle the interrupt and panic.

Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
---
 drivers/misc/vcpu_stall_detector.c | 41 ++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/vcpu_stall_detector.c b/drivers/misc/vcpu_stall_detector.c
index e2015c87f03f..c580cd7fd225 100644
--- a/drivers/misc/vcpu_stall_detector.c
+++ b/drivers/misc/vcpu_stall_detector.c
@@ -32,6 +32,7 @@
 struct vcpu_stall_detect_config {
 	u32 clock_freq_hz;
 	u32 stall_timeout_sec;
+	int ppi_irq;
 
 	void __iomem *membase;
 	struct platform_device *dev;
@@ -77,6 +78,12 @@ vcpu_stall_detect_timer_fn(struct hrtimer *hrtimer)
 	return HRTIMER_RESTART;
 }
 
+static irqreturn_t vcpu_stall_detector_irq(int irq, void *dev)
+{
+	panic("vCPU stall detector");
+	return IRQ_HANDLED;
+}
+
 static int start_stall_detector_cpu(unsigned int cpu)
 {
 	u32 ticks, ping_timeout_ms;
@@ -132,7 +139,7 @@ static int stop_stall_detector_cpu(unsigned int cpu)
 
 static int vcpu_stall_detect_probe(struct platform_device *pdev)
 {
-	int ret;
+	int ret, irq, num_irqs;
 	struct resource *r;
 	void __iomem *membase;
 	u32 clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ;
@@ -169,9 +176,32 @@ static int vcpu_stall_detect_probe(struct platform_device *pdev)
 	vcpu_stall_config = (struct vcpu_stall_detect_config) {
 		.membase		= membase,
 		.clock_freq_hz		= clock_freq_hz,
-		.stall_timeout_sec	= stall_timeout_sec
+		.stall_timeout_sec	= stall_timeout_sec,
+		.ppi_irq		= -1,
 	};
 
+	num_irqs = platform_irq_count(pdev);
+	if (num_irqs < 0) {
+		dev_err(&pdev->dev, "Failed to get irqs\n");
+		ret = num_irqs;
+		goto err;
+	} else if (num_irqs > 1) {
+		dev_err(&pdev->dev, "Multipple irqs detected\n");
+		ret = -EINVAL;
+		goto err;
+	} else if (num_irqs == 1) {
+		irq = platform_get_irq(pdev, 0);
+		if ((irq > 0) && irq_is_percpu_devid(irq)) {
+			ret = request_percpu_irq(irq,
+						 vcpu_stall_detector_irq,
+						 "vcpu_stall_detector",
+						 vcpu_stall_detectors);
+			if (!ret)
+				vcpu_stall_config.ppi_irq = irq;
+
+		}
+	}
+
 	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
 				"virt/vcpu_stall_detector:online",
 				start_stall_detector_cpu,
@@ -184,6 +214,9 @@ static int vcpu_stall_detect_probe(struct platform_device *pdev)
 	vcpu_stall_config.hp_online = ret;
 	return 0;
 err:
+	if (vcpu_stall_config.ppi_irq > 0)
+		free_percpu_irq(vcpu_stall_config.ppi_irq,
+				vcpu_stall_detectors);
 	return ret;
 }
 
@@ -193,6 +226,10 @@ static void vcpu_stall_detect_remove(struct platform_device *pdev)
 
 	cpuhp_remove_state(vcpu_stall_config.hp_online);
 
+	if (vcpu_stall_config.ppi_irq > 0)
+		free_percpu_irq(vcpu_stall_config.ppi_irq,
+				vcpu_stall_detectors);
+
 	for_each_possible_cpu(cpu)
 		stop_stall_detector_cpu(cpu);
 }
-- 
2.45.1.288.g0e0cd299f1-goog