From: Like Xu <likexu@xxxxxxxxxxx>
If the PMU is broken due to firmware issues, check_hw_exists() will return
false but perf_get_x86_pmu_capability() will still return data from x86_pmu.
Likewise if some of the hotplug callbacks cannot be installed the contents
of x86_pmu will not be reverted.
Handle the failure in both cases by clearing x86_pmu if init_hw_perf_events()
or reverts to software events only.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/events/core.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 99cf67d63cf3..d23f3821daf5 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2095,14 +2095,15 @@ static int __init init_hw_perf_events(void)
}
if (err != 0) {
pr_cont("no PMU driver, software events only.\n");
- return 0;
+ err = 0;
+ goto out_bad_pmu;
}
pmu_check_apic();
/* sanity check that the hardware exists or is emulated */
if (!check_hw_exists(&pmu, x86_pmu.num_counters, x86_pmu.num_counters_fixed))
- return 0;
+ goto out_bad_pmu;
pr_cont("%s PMU driver.\n", x86_pmu.name);
@@ -2211,6 +2212,8 @@ static int __init init_hw_perf_events(void)
cpuhp_remove_state(CPUHP_AP_PERF_X86_STARTING);
out:
cpuhp_remove_state(CPUHP_PERF_X86_PREPARE);
+out_bad_pmu:
+ memset(&x86_pmu, 0, sizeof(x86_pmu));
return err;
}
early_initcall(init_hw_perf_events);
@@ -2982,6 +2985,11 @@ unsigned long perf_misc_flags(struct pt_regs *regs)
void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
{
+ if (!x86_pmu.name) {
+ memset(cap, 0, sizeof(*cap));
+ return;
+ }
+
cap->version = x86_pmu.version;
/*
* KVM doesn't support the hybrid PMU yet.
--
2.31.1
