KVM: In kernel PIT model

The patch moves the PIT model from userspace to kernel, and increases
the timer accuracy greatly.

[marcelo: make last_injected_time per-guest]

Signed-off-by: Sheng Yang <sheng.yang@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Tested-and-Acked-by: Alex Davis <alex14641@yahoo.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

5 files changed, 661 insertions, 1 deletions

diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index ffdd0b31078..4d0c22e11f1 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -6,7 +6,8 @@ common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o)
 
 EXTRA_CFLAGS += -Ivirt/kvm -Iarch/x86/kvm
 
-kvm-objs := $(common-objs) x86.o mmu.o x86_emulate.o i8259.o irq.o lapic.o
+kvm-objs := $(common-objs) x86.o mmu.o x86_emulate.o i8259.o irq.o lapic.o \
+	i8254.o
 obj-$(CONFIG_KVM) += kvm.o
 kvm-intel-objs = vmx.o
 obj-$(CONFIG_KVM_INTEL) += kvm-intel.o
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
new file mode 100644
index 00000000000..c7435093bbe
--- /dev/null
+++ b/arch/x86/kvm/i8254.c
@@ -0,0 +1,586 @@
+/*
+ * 8253/8254 interval timer emulation
+ *
+ * Copyright (c) 2003-2004 Fabrice Bellard
+ * Copyright (c) 2006 Intel Corporation
+ * Copyright (c) 2007 Keir Fraser, XenSource Inc
+ * Copyright (c) 2008 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * Authors:
+ *   Sheng Yang <sheng.yang@intel.com>
+ *   Based on QEMU and Xen.
+ */
+
+#include <linux/kvm_host.h>
+
+#include "irq.h"
+#include "i8254.h"
+
+#ifndef CONFIG_X86_64
+#define mod_64(x, y) ((x) - (y) * div64_64(x, y))
+#else
+#define mod_64(x, y) ((x) % (y))
+#endif
+
+#define RW_STATE_LSB 1
+#define RW_STATE_MSB 2
+#define RW_STATE_WORD0 3
+#define RW_STATE_WORD1 4
+
+/* Compute with 96 bit intermediate result: (a*b)/c */
+static u64 muldiv64(u64 a, u32 b, u32 c)
+{
+	union {
+		u64 ll;
+		struct {
+			u32 low, high;
+		} l;
+	} u, res;
+	u64 rl, rh;
+
+	u.ll = a;
+	rl = (u64)u.l.low * (u64)b;
+	rh = (u64)u.l.high * (u64)b;
+	rh += (rl >> 32);
+	res.l.high = div64_64(rh, c);
+	res.l.low = div64_64(((mod_64(rh, c) << 32) + (rl & 0xffffffff)), c);
+	return res.ll;
+}
+
+static void pit_set_gate(struct kvm *kvm, int channel, u32 val)
+{
+	struct kvm_kpit_channel_state *c =
+		&kvm->arch.vpit->pit_state.channels[channel];
+
+	WARN_ON(!mutex_is_locked(&kvm->arch.vpit->pit_state.lock));
+
+	switch (c->mode) {
+	default:
+	case 0:
+	case 4:
+		/* XXX: just disable/enable counting */
+		break;
+	case 1:
+	case 2:
+	case 3:
+	case 5:
+		/* Restart counting on rising edge. */
+		if (c->gate < val)
+			c->count_load_time = ktime_get();
+		break;
+	}
+
+	c->gate = val;
+}
+
+int pit_get_gate(struct kvm *kvm, int channel)
+{
+	WARN_ON(!mutex_is_locked(&kvm->arch.vpit->pit_state.lock));
+
+	return kvm->arch.vpit->pit_state.channels[channel].gate;
+}
+
+static int pit_get_count(struct kvm *kvm, int channel)
+{
+	struct kvm_kpit_channel_state *c =
+		&kvm->arch.vpit->pit_state.channels[channel];
+	s64 d, t;
+	int counter;
+
+	WARN_ON(!mutex_is_locked(&kvm->arch.vpit->pit_state.lock));
+
+	t = ktime_to_ns(ktime_sub(ktime_get(), c->count_load_time));
+	d = muldiv64(t, KVM_PIT_FREQ, NSEC_PER_SEC);
+
+	switch (c->mode) {
+	case 0:
+	case 1:
+	case 4:
+	case 5:
+		counter = (c->count - d) & 0xffff;
+		break;
+	case 3:
+		/* XXX: may be incorrect for odd counts */
+		counter = c->count - (mod_64((2 * d), c->count));
+		break;
+	default:
+		counter = c->count - mod_64(d, c->count);
+		break;
+	}
+	return counter;
+}
+
+static int pit_get_out(struct kvm *kvm, int channel)
+{
+	struct kvm_kpit_channel_state *c =
+		&kvm->arch.vpit->pit_state.channels[channel];
+	s64 d, t;
+	int out;
+
+	WARN_ON(!mutex_is_locked(&kvm->arch.vpit->pit_state.lock));
+
+	t = ktime_to_ns(ktime_sub(ktime_get(), c->count_load_time));
+	d = muldiv64(t, KVM_PIT_FREQ, NSEC_PER_SEC);
+
+	switch (c->mode) {
+	default:
+	case 0:
+		out = (d >= c->count);
+		break;
+	case 1:
+		out = (d < c->count);
+		break;
+	case 2:
+		out = ((mod_64(d, c->count) == 0) && (d != 0));
+		break;
+	case 3:
+		out = (mod_64(d, c->count) < ((c->count + 1) >> 1));
+		break;
+	case 4:
+	case 5:
+		out = (d == c->count);
+		break;
+	}
+
+	return out;
+}
+
+static void pit_latch_count(struct kvm *kvm, int channel)
+{
+	struct kvm_kpit_channel_state *c =
+		&kvm->arch.vpit->pit_state.channels[channel];
+
+	WARN_ON(!mutex_is_locked(&kvm->arch.vpit->pit_state.lock));
+
+	if (!c->count_latched) {
+		c->latched_count = pit_get_count(kvm, channel);
+		c->count_latched = c->rw_mode;
+	}
+}
+
+static void pit_latch_status(struct kvm *kvm, int channel)
+{
+	struct kvm_kpit_channel_state *c =
+		&kvm->arch.vpit->pit_state.channels[channel];
+
+	WARN_ON(!mutex_is_locked(&kvm->arch.vpit->pit_state.lock));
+
+	if (!c->status_latched) {
+		/* TODO: Return NULL COUNT (bit 6). */
+		c->status = ((pit_get_out(kvm, channel) << 7) |
+				(c->rw_mode << 4) |
+				(c->mode << 1) |
+				c->bcd);
+		c->status_latched = 1;
+	}
+}
+
+int __pit_timer_fn(struct kvm_kpit_state *ps)
+{
+	struct kvm_vcpu *vcpu0 = ps->pit->kvm->vcpus[0];
+	struct kvm_kpit_timer *pt = &ps->pit_timer;
+
+	atomic_inc(&pt->pending);
+	smp_mb__after_atomic_inc();
+	/* FIXME: handle case where the guest is in guest mode */
+	if (vcpu0 && waitqueue_active(&vcpu0->wq)) {
+		vcpu0->arch.mp_state = VCPU_MP_STATE_RUNNABLE;
+		wake_up_interruptible(&vcpu0->wq);
+	}
+
+	pt->timer.expires = ktime_add_ns(pt->timer.expires, pt->period);
+	pt->scheduled = ktime_to_ns(pt->timer.expires);
+
+	return (pt->period == 0 ? 0 : 1);
+}
+
+static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
+{
+	struct kvm_kpit_state *ps;
+	int restart_timer = 0;
+
+	ps = container_of(data, struct kvm_kpit_state, pit_timer.timer);
+
+	restart_timer = __pit_timer_fn(ps);
+
+	if (restart_timer)
+		return HRTIMER_RESTART;
+	else
+		return HRTIMER_NORESTART;
+}
+
+static void destroy_pit_timer(struct kvm_kpit_timer *pt)
+{
+	pr_debug("pit: execute del timer!\n");
+	hrtimer_cancel(&pt->timer);
+}
+
+static void create_pit_timer(struct kvm_kpit_timer *pt, u32 val, int is_period)
+{
+	s64 interval;
+
+	interval = muldiv64(val, NSEC_PER_SEC, KVM_PIT_FREQ);
+
+	pr_debug("pit: create pit timer, interval is %llu nsec\n", interval);
+
+	/* TODO The new value only affected after the retriggered */
+	hrtimer_cancel(&pt->timer);
+	pt->period = (is_period == 0) ? 0 : interval;
+	pt->timer.function = pit_timer_fn;
+	atomic_set(&pt->pending, 0);
+
+	hrtimer_start(&pt->timer, ktime_add_ns(ktime_get(), interval),
+		      HRTIMER_MODE_ABS);
+}
+
+static void pit_load_count(struct kvm *kvm, int channel, u32 val)
+{
+	struct kvm_kpit_state *ps = &kvm->arch.vpit->pit_state;
+
+	WARN_ON(!mutex_is_locked(&ps->lock));
+
+	pr_debug("pit: load_count val is %d, channel is %d\n", val, channel);
+
+	/*
+	 * Though spec said the state of 8254 is undefined after power-up,
+	 * seems some tricky OS like Windows XP depends on IRQ0 interrupt
+	 * when booting up.
+	 * So here setting initialize rate for it, and not a specific number
+	 */
+	if (val == 0)
+		val = 0x10000;
+
+	ps->channels[channel].count_load_time = ktime_get();
+	ps->channels[channel].count = val;
+
+	if (channel != 0)
+		return;
+
+	/* Two types of timer
+	 * mode 1 is one shot, mode 2 is period, otherwise del timer */
+	switch (ps->channels[0].mode) {
+	case 1:
+		create_pit_timer(&ps->pit_timer, val, 0);
+		break;
+	case 2:
+		create_pit_timer(&ps->pit_timer, val, 1);
+		break;
+	default:
+		destroy_pit_timer(&ps->pit_timer);
+	}
+}
+
+static void pit_ioport_write(struct kvm_io_device *this,
+			     gpa_t addr, int len, const void *data)
+{
+	struct kvm_pit *pit = (struct kvm_pit *)this->private;
+	struct kvm_kpit_state *pit_state = &pit->pit_state;
+	struct kvm *kvm = pit->kvm;
+	int channel, access;
+	struct kvm_kpit_channel_state *s;
+	u32 val = *(u32 *) data;
+
+	val  &= 0xff;
+	addr &= KVM_PIT_CHANNEL_MASK;
+
+	mutex_lock(&pit_state->lock);
+
+	if (val != 0)
+		pr_debug("pit: write addr is 0x%x, len is %d, val is 0x%x\n",
+			  (unsigned int)addr, len, val);
+
+	if (addr == 3) {
+		channel = val >> 6;
+		if (channel == 3) {
+			/* Read-Back Command. */
+			for (channel = 0; channel < 3; channel++) {
+				s = &pit_state->channels[channel];
+				if (val & (2 << channel)) {
+					if (!(val & 0x20))
+						pit_latch_count(kvm, channel);
+					if (!(val & 0x10))
+						pit_latch_status(kvm, channel);
+				}
+			}
+		} else {
+			/* Select Counter <channel>. */
+			s = &pit_state->channels[channel];
+			access = (val >> 4) & KVM_PIT_CHANNEL_MASK;
+			if (access == 0) {
+				pit_latch_count(kvm, channel);
+			} else {
+				s->rw_mode = access;
+				s->read_state = access;
+				s->write_state = access;
+				s->mode = (val >> 1) & 7;
+				if (s->mode > 5)
+					s->mode -= 4;
+				s->bcd = val & 1;
+			}
+		}
+	} else {
+		/* Write Count. */
+		s = &pit_state->channels[addr];
+		switch (s->write_state) {
+		default:
+		case RW_STATE_LSB:
+			pit_load_count(kvm, addr, val);
+			break;
+		case RW_STATE_MSB:
+			pit_load_count(kvm, addr, val << 8);
+			break;
+		case RW_STATE_WORD0:
+			s->write_latch = val;
+			s->write_state = RW_STATE_WORD1;
+			break;
+		case RW_STATE_WORD1:
+			pit_load_count(kvm, addr, s->write_latch | (val << 8));
+			s->write_state = RW_STATE_WORD0;
+			break;
+		}
+	}
+
+	mutex_unlock(&pit_state->lock);
+}
+
+static void pit_ioport_read(struct kvm_io_device *this,
+			    gpa_t addr, int len, void *data)
+{
+	struct kvm_pit *pit = (struct kvm_pit *)this->private;
+	struct kvm_kpit_state *pit_state = &pit->pit_state;
+	struct kvm *kvm = pit->kvm;
+	int ret, count;
+	struct kvm_kpit_channel_state *s;
+
+	addr &= KVM_PIT_CHANNEL_MASK;
+	s = &pit_state->channels[addr];
+
+	mutex_lock(&pit_state->lock);
+
+	if (s->status_latched) {
+		s->status_latched = 0;
+		ret = s->status;
+	} else if (s->count_latched) {
+		switch (s->count_latched) {
+		default:
+		case RW_STATE_LSB:
+			ret = s->latched_count & 0xff;
+			s->count_latched = 0;
+			break;
+		case RW_STATE_MSB:
+			ret = s->latched_count >> 8;
+			s->count_latched = 0;
+			break;
+		case RW_STATE_WORD0:
+			ret = s->latched_count & 0xff;
+			s->count_latched = RW_STATE_MSB;
+			break;
+		}
+	} else {
+		switch (s->read_state) {
+		default:
+		case RW_STATE_LSB:
+			count = pit_get_count(kvm, addr);
+			ret = count & 0xff;
+			break;
+		case RW_STATE_MSB:
+			count = pit_get_count(kvm, addr);
+			ret = (count >> 8) & 0xff;
+			break;
+		case RW_STATE_WORD0:
+			count = pit_get_count(kvm, addr);
+			ret = count & 0xff;
+			s->read_state = RW_STATE_WORD1;
+			break;
+		case RW_STATE_WORD1:
+			count = pit_get_count(kvm, addr);
+			ret = (count >> 8) & 0xff;
+			s->read_state = RW_STATE_WORD0;
+			break;
+		}
+	}
+
+	if (len > sizeof(ret))
+		len = sizeof(ret);
+	memcpy(data, (char *)&ret, len);
+
+	mutex_unlock(&pit_state->lock);
+}
+
+static int pit_in_range(struct kvm_io_device *this, gpa_t addr)
+{
+	return ((addr >= KVM_PIT_BASE_ADDRESS) &&
+		(addr < KVM_PIT_BASE_ADDRESS + KVM_PIT_MEM_LENGTH));
+}
+
+static void speaker_ioport_write(struct kvm_io_device *this,
+				 gpa_t addr, int len, const void *data)
+{
+	struct kvm_pit *pit = (struct kvm_pit *)this->private;
+	struct kvm_kpit_state *pit_state = &pit->pit_state;
+	struct kvm *kvm = pit->kvm;
+	u32 val = *(u32 *) data;
+
+	mutex_lock(&pit_state->lock);
+	pit_state->speaker_data_on = (val >> 1) & 1;
+	pit_set_gate(kvm, 2, val & 1);
+	mutex_unlock(&pit_state->lock);
+}
+
+static void speaker_ioport_read(struct kvm_io_device *this,
+				gpa_t addr, int len, void *data)
+{
+	struct kvm_pit *pit = (struct kvm_pit *)this->private;
+	struct kvm_kpit_state *pit_state = &pit->pit_state;
+	struct kvm *kvm = pit->kvm;
+	unsigned int refresh_clock;
+	int ret;
+
+	/* Refresh clock toggles at about 15us. We approximate as 2^14ns. */
+	refresh_clock = ((unsigned int)ktime_to_ns(ktime_get()) >> 14) & 1;
+
+	mutex_lock(&pit_state->lock);
+	ret = ((pit_state->speaker_data_on << 1) | pit_get_gate(kvm, 2) |
+		(pit_get_out(kvm, 2) << 5) | (refresh_clock << 4));
+	if (len > sizeof(ret))
+		len = sizeof(ret);
+	memcpy(data, (char *)&ret, len);
+	mutex_unlock(&pit_state->lock);
+}
+
+static int speaker_in_range(struct kvm_io_device *this, gpa_t addr)
+{
+	return (addr == KVM_SPEAKER_BASE_ADDRESS);
+}
+
+struct kvm_pit *kvm_create_pit(struct kvm *kvm)
+{
+	int i;
+	struct kvm_pit *pit;
+	struct kvm_kpit_state *pit_state;
+	struct kvm_kpit_channel_state *c;
+
+	pit = kzalloc(sizeof(struct kvm_pit), GFP_KERNEL);
+	if (!pit)
+		return NULL;
+
+	mutex_init(&pit->pit_state.lock);
+	mutex_lock(&pit->pit_state.lock);
+
+	/* Initialize PIO device */
+	pit->dev.read = pit_ioport_read;
+	pit->dev.write = pit_ioport_write;
+	pit->dev.in_range = pit_in_range;
+	pit->dev.private = pit;
+	kvm_io_bus_register_dev(&kvm->pio_bus, &pit->dev);
+
+	pit->speaker_dev.read = speaker_ioport_read;
+	pit->speaker_dev.write = speaker_ioport_write;
+	pit->speaker_dev.in_range = speaker_in_range;
+	pit->speaker_dev.private = pit;
+	kvm_io_bus_register_dev(&kvm->pio_bus, &pit->speaker_dev);
+
+	kvm->arch.vpit = pit;
+	pit->kvm = kvm;
+
+	pit_state = &pit->pit_state;
+	pit_state->pit = pit;
+	hrtimer_init(&pit_state->pit_timer.timer,
+		     CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+	atomic_set(&pit_state->pit_timer.pending, 0);
+	for (i = 0; i < 3; i++) {
+		c = &pit_state->channels[i];
+		c->mode = 0xff;
+		c->gate = (i != 2);
+		pit_load_count(kvm, i, 0);
+	}
+
+	mutex_unlock(&pit->pit_state.lock);
+
+	pit->pit_state.inject_pending = 1;
+
+	return pit;
+}
+
+void kvm_free_pit(struct kvm *kvm)
+{
+	struct hrtimer *timer;
+
+	if (kvm->arch.vpit) {
+		mutex_lock(&kvm->arch.vpit->pit_state.lock);
+		timer = &kvm->arch.vpit->pit_state.pit_timer.timer;
+		hrtimer_cancel(timer);
+		mutex_unlock(&kvm->arch.vpit->pit_state.lock);
+		kfree(kvm->arch.vpit);
+	}
+}
+
+void __inject_pit_timer_intr(struct kvm *kvm)
+{
+	mutex_lock(&kvm->lock);
+	kvm_ioapic_set_irq(kvm->arch.vioapic, 0, 1);
+	kvm_ioapic_set_irq(kvm->arch.vioapic, 0, 0);
+	kvm_pic_set_irq(pic_irqchip(kvm), 0, 1);
+	kvm_pic_set_irq(pic_irqchip(kvm), 0, 0);
+	mutex_unlock(&kvm->lock);
+}
+
+void kvm_inject_pit_timer_irqs(struct kvm_vcpu *vcpu)
+{
+	struct kvm_pit *pit = vcpu->kvm->arch.vpit;
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_kpit_state *ps;
+
+	if (vcpu && pit) {
+		ps = &pit->pit_state;
+
+		/* Try to inject pending interrupts when:
+		 * 1. Pending exists
+		 * 2. Last interrupt was accepted or waited for too long time*/
+		if (atomic_read(&ps->pit_timer.pending) &&
+		    (ps->inject_pending ||
+		    (jiffies - ps->last_injected_time
+				>= KVM_MAX_PIT_INTR_INTERVAL))) {
+			ps->inject_pending = 0;
+			__inject_pit_timer_intr(kvm);
+			ps->last_injected_time = jiffies;
+		}
+	}
+}
+
+void kvm_pit_timer_intr_post(struct kvm_vcpu *vcpu, int vec)
+{
+	struct kvm_arch *arch = &vcpu->kvm->arch;
+	struct kvm_kpit_state *ps;
+
+	if (vcpu && arch->vpit) {
+		ps = &arch->vpit->pit_state;
+		if (atomic_read(&ps->pit_timer.pending) &&
+		(((arch->vpic->pics[0].imr & 1) == 0 &&
+		  arch->vpic->pics[0].irq_base == vec) ||
+		  (arch->vioapic->redirtbl[0].fields.vector == vec &&
+		  arch->vioapic->redirtbl[0].fields.mask != 1))) {
+			ps->inject_pending = 1;
+			atomic_dec(&ps->pit_timer.pending);
+			ps->channels[0].count_load_time = ktime_get();
+		}
+	}
+}
diff --git a/arch/x86/kvm/i8254.h b/arch/x86/kvm/i8254.h
new file mode 100644
index 00000000000..d77d6b795a1
--- /dev/null
+++ b/arch/x86/kvm/i8254.h
@@ -0,0 +1,61 @@
+#ifndef __I8254_H
+#define __I8254_H
+
+#include "iodev.h"
+
+struct kvm_kpit_timer {
+	struct hrtimer timer;
+	int irq;
+	s64 period; /* unit: ns */
+	s64 scheduled;
+	ktime_t last_update;
+	atomic_t pending;
+};
+
+struct kvm_kpit_channel_state {
+	u32 count; /* can be 65536 */
+	u16 latched_count;
+	u8 count_latched;
+	u8 status_latched;
+	u8 status;
+	u8 read_state;
+	u8 write_state;
+	u8 write_latch;
+	u8 rw_mode;
+	u8 mode;
+	u8 bcd; /* not supported */
+	u8 gate; /* timer start */
+	ktime_t count_load_time;
+};
+
+struct kvm_kpit_state {
+	struct kvm_kpit_channel_state channels[3];
+	struct kvm_kpit_timer pit_timer;
+	u32    speaker_data_on;
+	struct mutex lock;
+	struct kvm_pit *pit;
+	bool inject_pending; /* if inject pending interrupts */
+	unsigned long last_injected_time;
+};
+
+struct kvm_pit {
+	unsigned long base_addresss;
+	struct kvm_io_device dev;
+	struct kvm_io_device speaker_dev;
+	struct kvm *kvm;
+	struct kvm_kpit_state pit_state;
+};
+
+#define KVM_PIT_BASE_ADDRESS	    0x40
+#define KVM_SPEAKER_BASE_ADDRESS    0x61
+#define KVM_PIT_MEM_LENGTH	    4
+#define KVM_PIT_FREQ		    1193181
+#define KVM_MAX_PIT_INTR_INTERVAL   HZ / 100
+#define KVM_PIT_CHANNEL_MASK	    0x3
+
+void kvm_inject_pit_timer_irqs(struct kvm_vcpu *vcpu);
+void kvm_pit_timer_intr_post(struct kvm_vcpu *vcpu, int vec);
+struct kvm_pit *kvm_create_pit(struct kvm *kvm);
+void kvm_free_pit(struct kvm *kvm);
+
+#endif
diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index e5714759e97..dbfe21c99c4 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -23,6 +23,7 @@
 #include <linux/kvm_host.h>
 
 #include "irq.h"
+#include "i8254.h"
 
 /*
  * check if there is pending interrupt without
@@ -66,6 +67,7 @@ EXPORT_SYMBOL_GPL(kvm_cpu_get_interrupt);
 void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu)
 {
 	kvm_inject_apic_timer_irqs(vcpu);
+	kvm_inject_pit_timer_irqs(vcpu);
 	/* TODO: PIT, RTC etc. */
 }
 EXPORT_SYMBOL_GPL(kvm_inject_pending_timer_irqs);
@@ -73,6 +75,7 @@ EXPORT_SYMBOL_GPL(kvm_inject_pending_timer_irqs);
 void kvm_timer_intr_post(struct kvm_vcpu *vcpu, int vec)
 {
 	kvm_apic_timer_intr_post(vcpu, vec);
+	kvm_pit_timer_intr_post(vcpu, vec);
 	/* TODO: PIT, RTC etc. */
 }
 EXPORT_SYMBOL_GPL(kvm_timer_intr_post);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bf78d6522d3..c33a4578132 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -17,6 +17,7 @@
 #include <linux/kvm_host.h>
 #include "irq.h"
 #include "mmu.h"
+#include "i8254.h"
 
 #include <linux/clocksource.h>
 #include <linux/kvm.h>
@@ -818,6 +819,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_SET_TSS_ADDR:
 	case KVM_CAP_EXT_CPUID:
 	case KVM_CAP_CLOCKSOURCE:
+	case KVM_CAP_PIT:
 		r = 1;
 		break;
 	case KVM_CAP_VAPIC:
@@ -1594,6 +1596,12 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		} else
 			goto out;
 		break;
+	case KVM_CREATE_PIT:
+		r = -ENOMEM;
+		kvm->arch.vpit = kvm_create_pit(kvm);
+		if (kvm->arch.vpit)
+			r = 0;
+		break;
 	case KVM_IRQ_LINE: {
 		struct kvm_irq_level irq_event;
 
@@ -3372,6 +3380,7 @@ static void kvm_free_vcpus(struct kvm *kvm)
 
 void kvm_arch_destroy_vm(struct kvm *kvm)
 {
+	kvm_free_pit(kvm);
 	kfree(kvm->arch.vpic);
 	kfree(kvm->arch.vioapic);
 	kvm_free_vcpus(kvm);