KVM: make halt_poll_ns per-vCPU

Change halt_poll_ns into per-VCPU variable, seeded from module parameter,
to allow greater flexibility.

Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 81089cf..1bef9e2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -242,6 +242,7 @@
 	int sigset_active;
 	sigset_t sigset;
 	struct kvm_vcpu_stat stat;
+	unsigned int halt_poll_ns;
 
 #ifdef CONFIG_HAS_IOMEM
 	int mmio_needed;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d8db2f8f..c06e57c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -217,6 +217,7 @@
 	vcpu->kvm = kvm;
 	vcpu->vcpu_id = id;
 	vcpu->pid = NULL;
+	vcpu->halt_poll_ns = 0;
 	init_waitqueue_head(&vcpu->wq);
 	kvm_async_pf_vcpu_init(vcpu);
 
@@ -1930,8 +1931,8 @@
 	bool waited = false;
 
 	start = cur = ktime_get();
-	if (halt_poll_ns) {
-		ktime_t stop = ktime_add_ns(ktime_get(), halt_poll_ns);
+	if (vcpu->halt_poll_ns) {
+		ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
 
 		do {
 			/*