KVM: x86: Explicitly zero-initialize on-stack CPUID unions

commit bc52ae0a708cb6fa3926d11c88e3c55e1171b4a1 upstream.

Explicitly zero/empty-initialize the unions used for PMU related CPUID
entries, instead of manually zeroing all fields (hopefully), or in the
case of 0x80000022, relying on the compiler to clobber the uninitialized
bitfields.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Message-ID: <20250315024102.2361628-1-seanjc@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 5fb12d9c71befaa8f39d6e4c91807f7113c70911..a6cffeff75d40b9b596a82ea69f1796caa0d5aaf 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1011,8 +1011,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
                }
                break;
        case 0xa: { /* Architectural Performance Monitoring */
-               union cpuid10_eax eax;
-               union cpuid10_edx edx;
+               union cpuid10_eax eax = { };
+               union cpuid10_edx edx = { };
 
                if (!enable_pmu || !static_cpu_has(X86_FEATURE_ARCH_PERFMON)) {
                        entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
@@ -1028,8 +1028,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 
                if (kvm_pmu_cap.version)
                        edx.split.anythread_deprecated = 1;
-               edx.split.reserved1 = 0;
-               edx.split.reserved2 = 0;
 
                entry->eax = eax.full;
                entry->ebx = kvm_pmu_cap.events_mask;
@@ -1303,7 +1301,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
                break;
        /* AMD Extended Performance Monitoring and Debug */
        case 0x80000022: {
-               union cpuid_0x80000022_ebx ebx;
+               union cpuid_0x80000022_ebx ebx = { };
 
                entry->ecx = entry->edx = 0;
                if (!enable_pmu || !kvm_cpu_cap_has(X86_FEATURE_PERFMON_V2)) {