KVM: x86/pmu: Don't try to get perf capabilities for hybrid CPUs

Explicitly zero kvm_host_pmu instead of attempting to get the perf PMU
capabilities when running on a hybrid CPU to avoid running afoul of perf's
sanity check.

------------[ cut here ]------------
WARNING: arch/x86/events/core.c:3089 at perf_get_x86_pmu_capability+0xd/0xc0,
Call Trace:
<TASK>
kvm_x86_vendor_init+0x1b0/0x1a40 [kvm]
vmx_init+0xdb/0x260 [kvm_intel]
vt_init+0x12/0x9d0 [kvm_intel]
do_one_initcall+0x60/0x3f0
do_init_module+0x97/0x2b0
load_module+0x2d08/0x2e30
init_module_from_file+0x96/0xe0
idempotent_init_module+0x117/0x330
__x64_sys_finit_module+0x73/0xe0

Always read the capabilities for non-hybrid CPUs, i.e. don't entirely
revert to reading capabilities if and only if KVM wants to use a PMU, as
it may be useful to have the host PMU capabilities available, e.g. if only
or debug.

Reported-by: Chaitanya Kumar Borah <[e-mail]>
Closes: https://lore.kernel.org/all/[e-mail]/
Fixes: 51f34b1e650f ("KVM: x86/pmu: Snapshot host (i.e. perf's) reported PMU capabilities")
Suggested-by: Sean Christopherson <[e-mail]>
Signed-off-by: Dapeng Mi <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
[sean: rework changelog, call out hybrid CPUs in shortlog]
Signed-off-by: Sean Christopherson <[e-mail]>

arch/x86/kvm/pmu.c

···
 	bool is_intel = boot_cpu_data.x86_vendor == X86_VENDOR_INTEL;
 	int min_nr_gp_ctrs = pmu_ops->MIN_NR_GP_COUNTERS;
 
-	perf_get_x86_pmu_capability(&kvm_host_pmu);
-
 	/*
 	 * Hybrid PMUs don't play nice with virtualization without careful
 	 * configuration by userspace, and KVM's APIs for reporting supported
 	 * vPMU features do not account for hybrid PMUs.  Disable vPMU support
 	 * for hybrid PMUs until KVM gains a way to let userspace opt-in.
 	 */
-	if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU))
+	if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU)) {
 		enable_pmu = false;
+		memset(&kvm_host_pmu, 0, sizeof(kvm_host_pmu));
+	} else {
+		perf_get_x86_pmu_capability(&kvm_host_pmu);
+	}
 
 	if (enable_pmu) {
 		/*