KVM: nVMX: Clean up and fix pin-based execution controls

Only interrupt and NMI exiting are mandatory for KVM to work, thus can
be exposed to the guest unconditionally, virtual NMI exiting is
optional. So we must not advertise it unless the host supports it.

Introduce the symbolic constant PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR at
this chance.
Reviewed-by: : Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

arch/x86/include/asm/vmx.h

@@ -71,6 +71,8 @@
 #define PIN_BASED_NMI_EXITING                   0x00000008
 #define PIN_BASED_VIRTUAL_NMIS                  0x00000020
 
+#define PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR	0x00000016
+
 #define VM_EXIT_SAVE_DEBUG_CONTROLS             0x00000002
 #define VM_EXIT_HOST_ADDR_SPACE_SIZE            0x00000200
 #define VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL      0x00001000

arch/x86/kvm/vmx.c

@@ -2040,14 +2040,16 @@ static __init void nested_vmx_setup_ctls_msrs(void)
 	 */
 
 	/* pin-based controls */
+	rdmsr(MSR_IA32_VMX_PINBASED_CTLS,
+	      nested_vmx_pinbased_ctls_low, nested_vmx_pinbased_ctls_high);
 	/*
 	 * According to the Intel spec, if bit 55 of VMX_BASIC is off (as it is
 	 * in our case), bits 1, 2 and 4 (i.e., 0x16) must be 1 in this MSR.
 	 */
-	nested_vmx_pinbased_ctls_low = 0x16 ;
-	nested_vmx_pinbased_ctls_high = 0x16 |
-		PIN_BASED_EXT_INTR_MASK | PIN_BASED_NMI_EXITING |
-		PIN_BASED_VIRTUAL_NMIS;
+	nested_vmx_pinbased_ctls_low |= PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR;
+	nested_vmx_pinbased_ctls_high &= PIN_BASED_EXT_INTR_MASK |
+		PIN_BASED_NMI_EXITING | PIN_BASED_VIRTUAL_NMIS;
+	nested_vmx_pinbased_ctls_high |= PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR;
 
 	/*
 	 * Exit controls