KVM: Make EFER reads safe when EFER does not exist

(cherry picked from commit e286e86e6d2042d67d09244aa0e05ffef75c9d54)

Some processors don't have EFER; don't oops if userspace wants us to
read EFER when we check NX.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1454992e6ace17d8d194448748bd1f4258749f71..662cf12d1db9436ea06e844ae7fce19219ba98d3 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -983,9 +983,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 
 static int is_efer_nx(void)
 {
-       u64 efer;
+       unsigned long long efer = 0;
 
-       rdmsrl(MSR_EFER, efer);
+       rdmsrl_safe(MSR_EFER, &efer);
        return efer & EFER_NX;
 }