KVM: vmx: write HOST_IA32_EFER in vmx_set_constant_host_state()

EFER is constant in the host and writing it once during setup means
we can skip writing the host value in add_atomic_switch_msr_special().

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2d120de..5367afe 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2696,7 +2696,8 @@ static void add_atomic_switch_msr_special(struct vcpu_vmx *vmx,
                u64 guest_val, u64 host_val)
 {
        vmcs_write64(guest_val_vmcs, guest_val);
-       vmcs_write64(host_val_vmcs, host_val);
+       if (host_val_vmcs != HOST_IA32_EFER)
+               vmcs_write64(host_val_vmcs, host_val);
        vm_entry_controls_setbit(vmx, entry);
        vm_exit_controls_setbit(vmx, exit);
 }
@@ -6333,6 +6334,9 @@ static void vmx_set_constant_host_state(struct vcpu_vmx *vmx)
                rdmsr(MSR_IA32_CR_PAT, low32, high32);
                vmcs_write64(HOST_IA32_PAT, low32 | ((u64) high32 << 32));
        }
+
+       if (cpu_has_load_ia32_efer)
+               vmcs_write64(HOST_IA32_EFER, host_efer);
 }
 
 static void set_cr4_guest_host_mask(struct vcpu_vmx *vmx)