[PATCH 068/104] KVM: Emulate hlt in the kernel

Avi Kivity
2007-09-17T08:44:53Z

From: Eddie Dong <eddie.dong@intel.com>

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>
---
drivers/kvm/i8259.c | 3 +++
drivers/kvm/irq.c | 4 ++++
drivers/kvm/kvm.h | 2 ++
drivers/kvm/kvm_main.c | 41 +++++++++++++++++++++++++++++++++++------
drivers/kvm/svm.c | 9 ++++++---
drivers/kvm/vmx.c | 8 ++++++--
include/linux/kvm.h | 1 +
7 files changed, 57 insertions(+), 11 deletions(-)

diff --git a/drivers/kvm/i8259.c b/drivers/kvm/i8259.c
index 40ad104..ee6030d 100644
--- a/drivers/kvm/i8259.c
+++ b/drivers/kvm/i8259.c
@@ -413,8 +413,11 @@ static void picdev_read(struct kvm_io_device *this,
static void pic_irq_request(void *opaque, int level)
{
struct kvm *kvm = opaque;
+ struct kvm_vcpu *vcpu = kvm->vcpus[0];

pic_irqchip(kvm)->output = level;
+ if (vcpu)
+ kvm_vcpu_kick(vcpu);
}

struct kvm_pic *kvm_create_pic(struct kvm *kvm)
diff --git a/drivers/kvm/irq.c b/drivers/kvm/irq.c
index 5265f82..e09cd65 100644
--- a/drivers/kvm/irq.c
+++ b/drivers/kvm/irq.c
@@ -70,6 +70,10 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
{
int ipi_pcpu = vcpu->cpu;

+ if (waitqueue_active(&vcpu->wq)) {
+ wake_up_interruptible(&vcpu->wq);
+ ++vcpu->stat.halt_wakeup;
+ }
if (vcpu->guest_mode)
smp_call_function_single(ipi_pcpu, vcpu_kick_intr, vcpu, 0, 0);
}
diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index 0a11b0f..f69b482 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -231,6 +231,7 @@ struct kvm_stat {
u32 signal_exits;
u32 irq_window_exits;
u32 halt_exits;
+ u32 halt_wakeup;
u32 request_irq_exits;
u32 irq_exits;
u32 light_exits;
@@ -353,6 +354,7 @@ struct kvm_vcpu {
gva_t mmio_fault_cr2;
struct kvm_pio_request pio;
void *pio_data;
+ wait_queue_head_t wq;

int sigset_active;
sigset_t sigset;
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 @@ static struct kvm_stats_debugfs_item {
{ "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 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
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 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
}
EXPORT_SYMBOL_GPL(emulate_instruction);

-int kvm_emulate_halt(struct kvm_vcpu *vcpu)
+/*
+ * The vCPU has executed a HLT instruction with in-kernel mode enabled.
+ */
+static void kvm_vcpu_kernel_halt(struct kvm_vcpu *vcpu)
{
- if (vcpu->irq_summary ||
- (irqchip_in_kernel(vcpu->kvm) && kvm_cpu_has_interrupt(vcpu)))
- return 1;
+ 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);
+ }

- vcpu->run->exit_reason = KVM_EXIT_HLT;
+ remove_wait_queue(&vcpu->wq, &wait);
+ set_current_state(TASK_RUNNING);
+}
+
+int kvm_emulate_halt(struct kvm_vcpu *vcpu)
+{
++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 @@ static long kvm_dev_ioctl(struct file *filp,

switch (ext) {
case KVM_CAP_IRQCHIP:
+ case KVM_CAP_HLT:
r = 1;
break;
default:
diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
index d576451..a347b61 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -1398,9 +1398,12 @@ static void do_interrupt_requests(struct vcpu_svm *svm,
static void post_kvm_run_save(struct vcpu_svm *svm,
struct kvm_run *kvm_run)
{
- kvm_run->ready_for_interrupt_injection
- = (svm->vcpu.interrupt_window_open &&
- svm->vcpu.irq_summary == 0);
+ if (irqchip_in_kernel(svm->vcpu.kvm))
+ kvm_run->ready_for_interrupt_injection = 1;
+ else
+ kvm_run->ready_for_interrupt_injection =
+ (svm->vcpu.interrupt_window_open &&
+ svm->vcpu.irq_summary == 0);
kvm_run->if_flag = (svm->vmcb->save.rflags & X86_EFLAGS_IF) != 0;
kvm_run->cr8 = get_cr8(&svm->vcpu);
kvm_run->apic_base = kvm_get_apic_base(&svm->vcpu);
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index c4cc17c..7ec8cf8 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -1961,8 +1961,12 @@ static void post_kvm_run_save(struct kvm_vcpu *vcpu,
kvm_run->if_flag = (vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) != 0;
kvm_run->cr8 = get_cr8(vcpu);
kvm_run->apic_base = kvm_get_apic_base(vcpu);
- kvm_run->ready_for_interrupt_injection = (vcpu->interrupt_window_open &&
- vcpu->irq_summary == 0);
+ if (irqchip_in_kernel(vcpu->kvm))
+ kvm_run->ready_for_interrupt_injection = 1;
+ else
+ kvm_run->ready_for_interrupt_injection =
+ (vcpu->interrupt_window_open &&
+ vcpu->irq_summary == 0);
}

static int handle_interrupt_window(struct kvm_vcpu *vcpu,
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 997bb3e..b0a13d1 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -283,6 +283,7 @@ struct kvm_signal_mask {
* Extension capability list.
*/
#define KVM_CAP_IRQCHIP 0
+#define KVM_CAP_HLT 1

/*
* ioctls for VM fds
--
1.5.3