[patch 25/48] KVM: Make EFER reads safe when EFER does not exist

From: Greg KH
Date: Fri Sep 04 2009 - 16:18:39 EST

2.6.27-stable review patch. If anyone has any objections, please let us know.

From: Avi Kivity <avi@xxxxxxxxxx>

(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@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
arch/x86/kvm/x86.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -983,9 +983,9 @@ void kvm_arch_vcpu_put(struct kvm_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;

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