KVM: Emulate hlt in the kernel
By sleeping in the kernel when hlt is executed, we simplify the in-kernel
guest interrupt path considerably.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index ffbdadd..4384364 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -76,6 +76,7 @@
{ "signal_exits", STAT_OFFSET(signal_exits) },
{ "irq_window", STAT_OFFSET(irq_window_exits) },
{ "halt_exits", STAT_OFFSET(halt_exits) },
+ { "halt_wakeup", STAT_OFFSET(halt_wakeup) },
{ "request_irq", STAT_OFFSET(request_irq_exits) },
{ "irq_exits", STAT_OFFSET(irq_exits) },
{ "light_exits", STAT_OFFSET(light_exits) },
@@ -248,6 +249,7 @@
vcpu->mmu.root_hpa = INVALID_PAGE;
vcpu->kvm = kvm;
vcpu->vcpu_id = id;
+ init_waitqueue_head(&vcpu->wq);
page = alloc_page(GFP_KERNEL | __GFP_ZERO);
if (!page) {
@@ -1307,15 +1309,41 @@
}
EXPORT_SYMBOL_GPL(emulate_instruction);
+/*
+ * The vCPU has executed a HLT instruction with in-kernel mode enabled.
+ */
+static void kvm_vcpu_kernel_halt(struct kvm_vcpu *vcpu)
+{
+ DECLARE_WAITQUEUE(wait, current);
+
+ add_wait_queue(&vcpu->wq, &wait);
+
+ /*
+ * We will block until either an interrupt or a signal wakes us up
+ */
+ while(!(irqchip_in_kernel(vcpu->kvm) && kvm_cpu_has_interrupt(vcpu))
+ && !vcpu->irq_summary
+ && !signal_pending(current)) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ vcpu_put(vcpu);
+ schedule();
+ vcpu_load(vcpu);
+ }
+
+ remove_wait_queue(&vcpu->wq, &wait);
+ set_current_state(TASK_RUNNING);
+}
+
int kvm_emulate_halt(struct kvm_vcpu *vcpu)
{
- if (vcpu->irq_summary ||
- (irqchip_in_kernel(vcpu->kvm) && kvm_cpu_has_interrupt(vcpu)))
- return 1;
-
- vcpu->run->exit_reason = KVM_EXIT_HLT;
++vcpu->stat.halt_exits;
- return 0;
+ if (irqchip_in_kernel(vcpu->kvm)) {
+ kvm_vcpu_kernel_halt(vcpu);
+ return 1;
+ } else {
+ vcpu->run->exit_reason = KVM_EXIT_HLT;
+ return 0;
+ }
}
EXPORT_SYMBOL_GPL(kvm_emulate_halt);
@@ -2916,6 +2944,7 @@
switch (ext) {
case KVM_CAP_IRQCHIP:
+ case KVM_CAP_HLT:
r = 1;
break;
default: