Commit 916e3a4f authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

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: default avatarLike Xu <likexu@tencent.com>
Signed-off-by: default avatarLike Xu <likexu@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 92d80178

arch/x86/events/core.c

+10 −2
Original line number Diff line number Diff line
@@ -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.