KVM: x86: Fix handling of pending signal on uninitialized AP

KVM API says that KVM_RUN will return with -EINTR when a signal is
pending. However, if a vCPU is in KVM_MP_STATE_UNINITIALIZED, then
the return value is unconditionally -EAGAIN.

Copy over some code from vcpu_run(), so that the case of a pending
signal results in the expected return value.
Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/x86.c

@@ -7235,6 +7235,11 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		kvm_apic_accept_events(vcpu);
 		kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 		r = -EAGAIN;
+		if (signal_pending(current)) {
+			r = -EINTR;
+			vcpu->run->exit_reason = KVM_EXIT_INTR;
+			++vcpu->stat.signal_exits;
+		}
 		goto out;
 	}