KVM: x86: Use DR_TRAP_BITS instead of hard-coded 15

Make all code consistent with kvm_deliver_exception_payload() by using
appropriate symbolic constant instead of hard-coded number.
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/emulate.c

@@ -4260,7 +4260,7 @@ static int check_dr_read(struct x86_emulate_ctxt *ctxt)
 		ulong dr6;
 
 		ctxt->ops->get_dr(ctxt, 6, &dr6);
-		dr6 &= ~15;
+		dr6 &= ~DR_TRAP_BITS;
 		dr6 |= DR6_BD | DR6_RTM;
 		ctxt->ops->set_dr(ctxt, 6, dr6);
 		return emulate_db(ctxt);

arch/x86/kvm/vmx/vmx.c

@@ -4521,7 +4521,7 @@ static int handle_exception(struct kvm_vcpu *vcpu)
 		dr6 = vmcs_readl(EXIT_QUALIFICATION);
 		if (!(vcpu->guest_debug &
 		      (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))) {
-			vcpu->arch.dr6 &= ~15;
+			vcpu->arch.dr6 &= ~DR_TRAP_BITS;
 			vcpu->arch.dr6 |= dr6 | DR6_RTM;
 			if (is_icebp(intr_info))
 				skip_emulated_instruction(vcpu);
@@ -4766,7 +4766,7 @@ static int handle_dr(struct kvm_vcpu *vcpu)
 			vcpu->run->exit_reason = KVM_EXIT_DEBUG;
 			return 0;
 		} else {
-			vcpu->arch.dr6 &= ~15;
+			vcpu->arch.dr6 &= ~DR_TRAP_BITS;
 			vcpu->arch.dr6 |= DR6_BD | DR6_RTM;
 			kvm_queue_exception(vcpu, DB_VECTOR);
 			return 1;

arch/x86/kvm/x86.c

@@ -6392,7 +6392,7 @@ static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r)
 					   vcpu->arch.db);
 
 		if (dr6 != 0) {
-			vcpu->arch.dr6 &= ~15;
+			vcpu->arch.dr6 &= ~DR_TRAP_BITS;
 			vcpu->arch.dr6 |= dr6 | DR6_RTM;
 			kvm_queue_exception(vcpu, DB_VECTOR);
 			*r = EMULATE_DONE;