[PATCH] x86, kvm, vmx: Don't set LOAD_IA32_EFER when host and guest match

[Andy Lutomirski]

There's nothing to switch if the host and guest values are the same.
I am unable to find evidence that this makes any difference
whatsoever.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
---
 arch/x86/kvm/vmx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e72b9660e51c..c430b01b012b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1670,7 +1670,9 @@ static bool update_transition_efer(struct vcpu_vmx *vmx, int efer_offset)
 		guest_efer = vmx->vcpu.arch.efer;
 		if (!(guest_efer & EFER_LMA))
 			guest_efer &= ~EFER_LME;
-		add_atomic_switch_msr(vmx, MSR_EFER, guest_efer, host_efer);
+		if (guest_efer != host_efer)
+			add_atomic_switch_msr(vmx, MSR_EFER,
+					      guest_efer, host_efer);
 		return false;
 	}
 
-- 
1.9.3

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