KVM: X86: Add KVM_VCPU_PREEMPTED

The next patch will add another bit to the preempted field in
kvm_steal_time.  Define a constant for bit 0 (the only one that is
currently used).

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

arch/x86/include/uapi/asm/kvm_para.h

@@ -51,6 +51,8 @@ struct kvm_steal_time {
 	__u32 pad[11];
 };
 
+#define KVM_VCPU_PREEMPTED          (1 << 0)
+
 #define KVM_CLOCK_PAIRING_WALLCLOCK 0
 struct kvm_clock_pairing {
 	__s64 sec;

arch/x86/kernel/kvm.c

@@ -643,7 +643,7 @@ __visible bool __kvm_vcpu_is_preempted(long cpu)
 {
 	struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
 
-	return !!src->preempted;
+	return !!(src->preempted & KVM_VCPU_PREEMPTED);
 }
 PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted);
 

arch/x86/kvm/x86.c

@@ -2916,7 +2916,7 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
 	if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
 		return;
 
-	vcpu->arch.st.steal.preempted = 1;
+	vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
 
 	kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime,
 			&vcpu->arch.st.steal.preempted,