KVM: x86: Mask off reserved bits in CPUID.80000008H

KVM_GET_SUPPORTED_CPUID should only enumerate features that KVM
actually supports. The following ranges of CPUID.80000008H are reserved
and should be masked off:
    ECX[31:18]
    ECX[11:8]

In addition, the PerfTscSize field at ECX[17:16] should also be zero
because KVM does not set the PERFTSC bit at CPUID.80000001H.ECX[27].

Fixes: 4c6c3c2fac70 ("KVM: Sanitize cpuid")
Signed-off-by: Jim Mattson <jmattson@google.com>
Message-Id: <20220929225203.2234702-3-jmattson@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 8325a01cb1f17fa09624c68025c8ff5522062aba..489c028859e197442bbcfbbd19cd3a36106237fe 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1169,6 +1169,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
                        g_phys_as = phys_as;
 
                entry->eax = g_phys_as | (virt_as << 8);
+               entry->ecx &= ~(GENMASK(31, 16) | GENMASK(11, 8));
                entry->edx = 0;
                cpuid_entry_override(entry, CPUID_8000_0008_EBX);
                break;