[PATCH 4.9 26/30] KVM: x86: Mask off reserved bits in CPUID.80000008H

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From: Jim Mattson <jmattson@xxxxxxxxxx>

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@xxxxxxxxxx>
Message-Id: <20220929225203.2234702-3-jmattson@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/kvm/cpuid.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -647,6 +647,7 @@ static inline int __do_cpuid_ent(struct
 			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





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