[PATCH 1/1] drivers/perf: arm_pmu_acpi: avoid perf IRQ init when guest PMU is off

[wei@redhat.com (Wei Huang)]

We saw perf IRQ init failures when running Linux kernel in an ACPI
guest without PMU (i.e. pmu=off). This is because perf IRQ is not
present when pmu=off, but arm_pmu_acpi still tries to register
or unregister GSI. This patch addresses the problem by checking
gicc->performance_interrupt. If it is 0, which is the value set
by qemu when pmu=off, we skip the IRQ register/unregister process.

[    4.069470] bc00: 0000000000040b00 ffff0000089db190
[    4.070267] [<ffff000008134f80>] enable_percpu_irq+0xdc/0xe4
[    4.071192] [<ffff000008667cc4>] arm_perf_starting_cpu+0x108/0x10c
[    4.072200] [<ffff0000080cbdd4>] cpuhp_invoke_callback+0x14c/0x4ac
[    4.073210] [<ffff0000080ccd3c>] cpuhp_thread_fun+0xd4/0x11c
[    4.074132] [<ffff0000080f1394>] smpboot_thread_fn+0x1b4/0x1c4
[    4.075081] [<ffff0000080ec90c>] kthread+0x10c/0x138
[    4.075921] [<ffff0000080833c0>] ret_from_fork+0x10/0x50
[    4.076947] genirq: Setting trigger mode 4 for irq 43 failed
(gic_set_type+0x0/0x74)

Signed-off-by: Wei Huang <wei@redhat.com>
---
 drivers/perf/arm_pmu_acpi.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
index 34c862f..d6bb75d 100644
--- a/drivers/perf/arm_pmu_acpi.c
+++ b/drivers/perf/arm_pmu_acpi.c
@@ -29,6 +29,9 @@ static int arm_pmu_acpi_register_irq(int cpu)
 		return -EINVAL;
 
 	gsi = gicc->performance_interrupt;
+	if (!gsi)
+		return 0;
+
 	if (gicc->flags & ACPI_MADT_PERFORMANCE_IRQ_MODE)
 		trigger = ACPI_EDGE_SENSITIVE;
 	else
@@ -58,7 +61,8 @@ static void arm_pmu_acpi_unregister_irq(int cpu)
 		return;
 
 	gsi = gicc->performance_interrupt;
-	acpi_unregister_gsi(gsi);
+	if (gsi)
+		acpi_unregister_gsi(gsi);
 }
 
 static int arm_pmu_acpi_parse_irqs(void)
-- 
2.7.4