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x86: events: Do not return bogus capabilities if PMU is broken 

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.

Co-developed-by: Like Xu <likexu@tencent.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2022-06-01 05:45:17 -04:00
parent 92d80178a3
commit 916e3a4f95
1 changed files with 10 additions and 2 deletions
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12
arch/x86/events/core.c
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@ -2103,14 +2103,15 @@ 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);
@ -2219,6 +2220,8 @@ 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);
@ -2990,6 +2993,11 @@ unsigned long perf_misc_flags(struct pt_regs *regs)
void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
{
if (!x86_pmu_initialized()) {
memset(cap, 0, sizeof(*cap));
return;
}
cap->version = x86_pmu.version;
/*
* KVM doesn't support the hybrid PMU yet.