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>

7 files changed, 664 insertions, 1 deletions

diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index ffdd0b310784..4d0c22e11f1a 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 000000000000..c7435093bbee
--- /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 000000000000..d77d6b795a1f
--- /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 e5714759e97f..dbfe21c99c48 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 bf78d6522d3d..c33a4578132c 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);
diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h
index 49ced21e0290..26a313a09472 100644
--- a/include/asm-x86/kvm_host.h
+++ b/include/asm-x86/kvm_host.h
@@ -298,6 +298,7 @@ struct kvm_arch{
         struct list_head active_mmu_pages;
         struct kvm_pic *vpic;
         struct kvm_ioapic *vioapic;
+        struct kvm_pit *vpit;
 
         int round_robin_prev_vcpu;
         unsigned int tss_addr;
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index e92e70324ea1..cefa9a2c7b89 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -236,6 +236,7 @@ struct kvm_vapic_addr {
 #define KVM_CAP_CLOCKSOURCE 8
 #define KVM_CAP_NR_VCPUS 9       /* returns max vcpus per vm */
 #define KVM_CAP_NR_MEMSLOTS 10   /* returns max memory slots per vm */
+#define KVM_CAP_PIT 11
 
 /*
  * ioctls for VM fds
@@ -258,6 +259,7 @@ struct kvm_vapic_addr {
 #define KVM_IRQ_LINE              _IOW(KVMIO, 0x61, struct kvm_irq_level)
 #define KVM_GET_IRQCHIP           _IOWR(KVMIO, 0x62, struct kvm_irqchip)
 #define KVM_SET_IRQCHIP           _IOR(KVMIO,  0x63, struct kvm_irqchip)
+#define KVM_CREATE_PIT            _IO(KVMIO,  0x64)
 
 /*
  * ioctls for vcpu fds