KVM: x86: introduce kvm_can_use_hv_timer

Replace the ad hoc test in vmx_set_hv_timer with a test in the caller,
start_hv_timer.  This test is not Intel-specific and would be duplicated
when introducing the fast path for the TSC deadline MSR.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -110,11 +110,18 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic)
 	return apic->vcpu->vcpu_id;
 }
 
-bool kvm_can_post_timer_interrupt(struct kvm_vcpu *vcpu)
+static bool kvm_can_post_timer_interrupt(struct kvm_vcpu *vcpu)
 {
 	return pi_inject_timer && kvm_vcpu_apicv_active(vcpu);
 }
-EXPORT_SYMBOL_GPL(kvm_can_post_timer_interrupt);
+
+bool kvm_can_use_hv_timer(struct kvm_vcpu *vcpu)
+{
+	return kvm_x86_ops.set_hv_timer
+	       && !(kvm_mwait_in_guest(vcpu->kvm) ||
+		    kvm_can_post_timer_interrupt(vcpu));
+}
+EXPORT_SYMBOL_GPL(kvm_can_use_hv_timer);
 
 static bool kvm_use_posted_timer_interrupt(struct kvm_vcpu *vcpu)
 {
@@ -1788,7 +1795,7 @@ static bool start_hv_timer(struct kvm_lapic *apic)
 	bool expired;
 
 	WARN_ON(preemptible());
-	if (!kvm_x86_ops.set_hv_timer)
+	if (!kvm_can_use_hv_timer(vcpu))
 		return false;
 
 	if (!ktimer->tscdeadline)

arch/x86/kvm/lapic.h

@@ -250,7 +250,7 @@ void kvm_lapic_switch_to_hv_timer(struct kvm_vcpu *vcpu);
 void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu);
 bool kvm_lapic_hv_timer_in_use(struct kvm_vcpu *vcpu);
 void kvm_lapic_restart_hv_timer(struct kvm_vcpu *vcpu);
-bool kvm_can_post_timer_interrupt(struct kvm_vcpu *vcpu);
+bool kvm_can_use_hv_timer(struct kvm_vcpu *vcpu);
 
 static inline enum lapic_mode kvm_apic_mode(u64 apic_base)
 {

arch/x86/kvm/vmx/vmx.c

@@ -7405,10 +7405,6 @@ static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc,
 	u64 tscl, guest_tscl, delta_tsc, lapic_timer_advance_cycles;
 	struct kvm_timer *ktimer = &vcpu->arch.apic->lapic_timer;
 
-	if (kvm_mwait_in_guest(vcpu->kvm) ||
-		kvm_can_post_timer_interrupt(vcpu))
-		return -EOPNOTSUPP;
-
 	vmx = to_vmx(vcpu);
 	tscl = rdtsc();
 	guest_tscl = kvm_read_l1_tsc(vcpu, tscl);