KVM: Fix MAXPHYADDR calculation when cpuid does not support it

MAXPHYADDR is derived from cpuid 0x80000008, but when that isn't present, we
get some random value.

Fix by checking first that cpuid 0x80000008 is supported.

Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 33a40c544c7ab020701f97584fb3a2c0d8406e58..d65e481c5fa447d7ab66299fbac52188dfd8e121 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4171,9 +4171,13 @@ int cpuid_maxphyaddr(struct kvm_vcpu *vcpu)
 {
        struct kvm_cpuid_entry2 *best;
 
+       best = kvm_find_cpuid_entry(vcpu, 0x80000000, 0);
+       if (!best || best->eax < 0x80000008)
+               goto not_found;
        best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);
        if (best)
                return best->eax & 0xff;
+not_found:
        return 36;
 }