KVM: vmx: write HOST_IA32_EFER in vmx_set_constant_host_state()

Sean Christopherson · bonzini · commit 5a5e8a15d76e · 2018-10-17T00:29:59.000+02:00
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 &lt;sean.j.christopherson@intel.com&gt;
Reviewed-by: Jim Mattson &lt;jmattson@google.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
diff --git 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)

Original file line number	Diff line number	Diff line change
`@@ -2696,7 +2696,8 @@ static void add_atomic_switch_msr_special(struct vcpu_vmx *vmx,`
`2696`	`2696`	`u64 guest_val, u64 host_val)`
`2697`	`2697`	`{`
`2698`	`2698`	`vmcs_write64(guest_val_vmcs, guest_val);`
`2699`		`- vmcs_write64(host_val_vmcs, host_val);`
	`2699`	`+ if (host_val_vmcs != HOST_IA32_EFER)`
	`2700`	`+ vmcs_write64(host_val_vmcs, host_val);`
`2700`	`2701`	`vm_entry_controls_setbit(vmx, entry);`
`2701`	`2702`	`vm_exit_controls_setbit(vmx, exit);`
`2702`	`2703`	`}`
`@@ -6333,6 +6334,9 @@ static void vmx_set_constant_host_state(struct vcpu_vmx *vmx)`
`6333`	`6334`	`rdmsr(MSR_IA32_CR_PAT, low32, high32);`
`6334`	`6335`	`vmcs_write64(HOST_IA32_PAT, low32 \| ((u64) high32 << 32));`
`6335`	`6336`	`}`
	`6337`	`+`
	`6338`	`+ if (cpu_has_load_ia32_efer)`
	`6339`	`+ vmcs_write64(HOST_IA32_EFER, host_efer);`
`6336`	`6340`	`}`
`6337`	`6341`
`6338`	`6342`	`static void set_cr4_guest_host_mask(struct vcpu_vmx *vmx)`