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

commit 7030d8530e533844e2f4b0e7476498afcd324634 upstream.

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: 24c82e576b78 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 0489ffc3dfe5f3b0ad13c56797f8d77641ae67e1..768a765c49b0d5af8410d5628086a0f6421d04cd 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -680,6 +680,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, 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;
                /*
                 * IBRS, IBPB and VIRT_SSBD aren't necessarily present in