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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/vcpu_stall_detector.c

···
 struct vcpu_stall_detect_config {
 	u32 clock_freq_hz;
 	u32 stall_timeout_sec;
+	int ppi_irq;
 
 	void __iomem *membase;
 	struct platform_device *dev;
···
 			    ms_to_ktime(ping_timeout_ms));
 
 	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)
···
 
 static int vcpu_stall_detect_probe(struct platform_device *pdev)
 {
-	int ret;
+	int ret, irq;
 	struct resource *r;
 	void __iomem *membase;
 	u32 clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ;
···
 	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,
 	};
+
+	irq = platform_get_irq_optional(pdev, 0);
+	if (irq > 0) {
+		ret = request_percpu_irq(irq,
+					 vcpu_stall_detector_irq,
+					 "vcpu_stall_detector",
+					 vcpu_stall_detectors);
+		if (ret)
+			goto err;
+
+		vcpu_stall_config.ppi_irq = irq;
+	}
 
 	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
 				"virt/vcpu_stall_detector:online",
···
 	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;
 }
 
···
 	int cpu;
 
 	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);