Messages in this thread | | | Subject | Re: [PATCH 1/1] drivers/perf: arm_pmu_acpi: avoid perf IRQ init when guest PMU is off | From | Wei Huang <> | Date | Thu, 25 May 2017 10:49:49 -0500 |
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On 05/25/2017 10:28 AM, Will Deacon wrote: > Hi Wei, > > On Wed, May 24, 2017 at 09:36:41AM -0500, Wei Huang wrote: >> 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; > > So a GSI of zero means we return an IRQ of zero, which correctly gets > treated as "No ACPI PMU"...
Yes, returning 0 here and dmesg prints out "No ACPI PMU IRQ for CPU" is acceptable.
> >> 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); > > ... but then I don't see how we can get here, so I'll drop this hunk.
I am OK to drop it. It was added just to be cautious... Do you need another version from me or you will remove this hunk?
> > Will >
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