Move the atpit device model from userspace into vmm.ko for better

precision and lower latency.

Approved by:	grehan (co-mentor)

8 files changed, 395 insertions, 306 deletions

diff --git a/sys/amd64/include/vmm.h b/sys/amd64/include/vmm.h
index 890f765..d50e7bc 100644
--- a/sys/amd64/include/vmm.h
+++ b/sys/amd64/include/vmm.h
@@ -191,6 +191,7 @@ struct vmspace *vm_get_vmspace(struct vm *vm);
 int vm_assign_pptdev(struct vm *vm, int bus, int slot, int func);
 int vm_unassign_pptdev(struct vm *vm, int bus, int slot, int func);
 struct vatpic *vm_atpic(struct vm *vm);
+struct vatpit *vm_atpit(struct vm *vm);
 
 /*
  * Inject exception 'vme' into the guest vcpu. This function returns 0 on
diff --git a/sys/amd64/vmm/io/vatpit.c b/sys/amd64/vmm/io/vatpit.c
new file mode 100644
index 0000000..6e6ffb7
--- /dev/null
+++ b/sys/amd64/vmm/io/vatpit.c
@@ -0,0 +1,370 @@
+/*-
+ * Copyright (c) 2014 Tycho Nightingale <tycho.nightingale@pluribusnetworks.com>
+ * Copyright (c) 2011 NetApp, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY NETAPP, INC ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL NETAPP, INC OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/types.h>
+#include <sys/queue.h>
+#include <sys/cpuset.h>
+#include <sys/kernel.h>
+#include <sys/lock.h>
+#include <sys/malloc.h>
+#include <sys/mutex.h>
+#include <sys/systm.h>
+
+#include <machine/vmm.h>
+
+#include "vmm_ktr.h"
+#include "vatpic.h"
+#include "vioapic.h"
+#include "vatpit.h"
+
+static MALLOC_DEFINE(M_VATPIT, "atpit", "bhyve virtual atpit (8254)");
+
+#define	VATPIT_LOCK(vatpit)		mtx_lock_spin(&((vatpit)->mtx))
+#define	VATPIT_UNLOCK(vatpit)		mtx_unlock_spin(&((vatpit)->mtx))
+#define	VATPIT_LOCKED(vatpit)		mtx_owned(&((vatpit)->mtx))
+
+#define	TIMER_SEL_MASK		0xc0
+#define	TIMER_RW_MASK		0x30
+#define	TIMER_MODE_MASK		0x0f
+#define	TIMER_SEL_READBACK	0xc0
+
+#define	PIT_8254_FREQ		1193182
+#define	TIMER_DIV(freq, hz)	(((freq) + (hz) / 2) / (hz))
+
+struct vatpit_callout_arg {
+	struct vatpit	*vatpit;
+	int		channel_num;
+};
+
+
+struct channel {
+	int		mode;
+	uint16_t	initial;	/* initial counter value */
+	sbintime_t	now_sbt;	/* uptime when counter was loaded */
+	uint8_t		cr[2];
+	uint8_t		ol[2];
+	int		crbyte;
+	int		olbyte;
+	int		frbyte;
+	struct callout	callout;
+	sbintime_t	callout_sbt;	/* target time */
+	struct vatpit_callout_arg callout_arg;
+};
+
+struct vatpit {
+	struct vm	*vm;
+	struct mtx	mtx;
+
+	sbintime_t	freq_sbt;
+
+	struct channel	channel[3];
+};
+
+#define	VATPIT_CTR0(vatpit, fmt)					\
+	VM_CTR0((vatpit)->vm, fmt)
+
+#define	VATPIT_CTR1(vatpit, fmt, a1)					\
+	VM_CTR1((vatpit)->vm, fmt, a1)
+
+#define	VATPIT_CTR2(vatpit, fmt, a1, a2)				\
+	VM_CTR2((vatpit)->vm, fmt, a1, a2)
+
+#define	VATPIT_CTR3(vatpit, fmt, a1, a2, a3)				\
+	VM_CTR3((vatpit)->vm, fmt, a1, a2, a3)
+
+#define	VATPIT_CTR4(vatpit, fmt, a1, a2, a3, a4)			\
+	VM_CTR4((vatpit)->vm, fmt, a1, a2, a3, a4)
+
+static void pit_timer_start_cntr0(struct vatpit *vatpit);
+
+static void
+vatpit_callout_handler(void *a)
+{
+	struct vatpit_callout_arg *arg = a;
+	struct vatpit *vatpit;
+	struct callout *callout;
+	struct channel *c;
+
+	vatpit = arg->vatpit;
+	c = &vatpit->channel[arg->channel_num];
+	callout = &c->callout;
+
+	VATPIT_CTR1(vatpit, "atpit t%d fired", arg->channel_num);
+
+	VATPIT_LOCK(vatpit);
+
+	if (callout_pending(callout))		/* callout was reset */
+		goto done;
+
+	if (!callout_active(callout))		/* callout was stopped */
+		goto done;
+
+	callout_deactivate(callout);
+
+	if (c->mode == TIMER_RATEGEN) {
+		pit_timer_start_cntr0(vatpit);
+	}
+
+	vatpic_pulse_irq(vatpit->vm, 0);
+	vioapic_pulse_irq(vatpit->vm, 2);
+
+done:
+	VATPIT_UNLOCK(vatpit);
+	return;
+}
+
+static void
+pit_timer_start_cntr0(struct vatpit *vatpit)
+{
+	struct channel *c;
+	sbintime_t delta, precision;
+
+	c = &vatpit->channel[0];
+	if (c->initial != 0) {
+		delta = c->initial * vatpit->freq_sbt;
+		precision = delta >> tc_precexp;
+		c->callout_sbt = c->callout_sbt + delta;
+
+		callout_reset_sbt(&c->callout, c->callout_sbt,
+		    precision, vatpit_callout_handler, &c->callout_arg,
+		    C_ABSOLUTE);
+	}
+}
+
+static uint16_t
+pit_update_counter(struct vatpit *vatpit, struct channel *c, bool latch)
+{
+	uint16_t lval;
+	sbintime_t delta_ticks;
+
+	/* cannot latch a new value until the old one has been consumed */
+	if (latch && c->olbyte != 0)
+		return (0);
+
+	if (c->initial == 0) {
+		/*
+		 * This is possibly an o/s bug - reading the value of
+		 * the timer without having set up the initial value.
+		 *
+		 * The original user-space version of this code set
+		 * the timer to 100hz in this condition; do the same
+		 * here.
+		 */
+		c->initial = TIMER_DIV(PIT_8254_FREQ, 100);
+		c->now_sbt = sbinuptime();
+	}
+
+	delta_ticks = (sbinuptime() - c->now_sbt) / vatpit->freq_sbt;
+
+	lval = c->initial - delta_ticks % c->initial;
+
+	if (latch) {
+		c->olbyte = 2;
+		c->ol[1] = lval;		/* LSB */
+		c->ol[0] = lval >> 8;		/* MSB */
+	}
+
+	return (lval);
+}
+
+static int
+vatpit_update_mode(struct vatpit *vatpit, uint8_t val)
+{
+	struct channel *c;
+	int sel, rw, mode;
+
+	sel = val & TIMER_SEL_MASK;
+	rw = val & TIMER_RW_MASK;
+	mode = val & TIMER_MODE_MASK;
+
+	if (sel == TIMER_SEL_READBACK)
+		return (-1);
+
+	if (rw != TIMER_LATCH && rw != TIMER_16BIT)
+		return (-1);
+
+	if (rw != TIMER_LATCH) {
+		/*
+		 * Counter mode is not affected when issuing a
+		 * latch command.
+		 */
+		if (mode != TIMER_INTTC &&
+		    mode != TIMER_RATEGEN &&
+		    mode != TIMER_SQWAVE &&
+		    mode != TIMER_SWSTROBE)
+			return (-1);
+	}
+
+	c = &vatpit->channel[sel >> 6];
+	if (rw == TIMER_LATCH)
+		pit_update_counter(vatpit, c, true);
+	else {
+		c->mode = mode;
+		c->olbyte = 0;	/* reset latch after reprogramming */
+	}
+
+	return (0);
+}
+
+static int
+vatpit_get_out(struct vatpit *vatpit, int channel)
+{
+	struct channel *c;
+	sbintime_t delta_ticks;
+	int out;
+
+	c = &vatpit->channel[channel];
+
+	switch (c->mode) {
+	case TIMER_INTTC:
+		delta_ticks = (sbinuptime() - c->now_sbt) / vatpit->freq_sbt;
+		out = ((c->initial - delta_ticks) <= 0);
+		break;
+	default:
+		out = 0;
+		break;
+	}
+
+	return (out);
+}
+
+int
+vatpit_handler(void *vm, int vcpuid, struct vm_exit *vmexit)
+{
+	struct vatpit *vatpit;
+	struct channel *c;
+	int port;
+	uint8_t val;
+	int error;
+
+	vatpit = vm_atpit(vm);
+
+	if (vmexit->u.inout.bytes != 1)
+		return (-1);
+
+	val = vmexit->u.inout.eax;
+	port = vmexit->u.inout.port;
+
+	if (port == TIMER_MODE) {
+		if (vmexit->u.inout.in != 0) {
+			VATPIT_CTR0(vatpit, "vatpit attempt to read mode");
+			return (-1);
+		}
+
+		VATPIT_LOCK(vatpit);
+		error = vatpit_update_mode(vatpit, val);
+		VATPIT_UNLOCK(vatpit);
+
+		return (error);
+	}
+
+	/* counter ports */
+	KASSERT(port >= TIMER_CNTR0 && vmexit->u.inout.port <= TIMER_CNTR2,
+	    ("invalid port 0x%x", port));
+	c = &vatpit->channel[port - TIMER_CNTR0];
+
+	VATPIT_LOCK(vatpit);
+	if (vmexit->u.inout.in) {
+		/*
+		 * The spec says that once the output latch is completely
+		 * read it should revert to "following" the counter. Use
+		 * the free running counter for this case (i.e. Linux
+		 * TSC calibration). Assuming the access mode is 16-bit,
+		 * toggle the MSB/LSB bit on each read.
+		 */
+		if (c->olbyte == 0) {
+			uint16_t tmp;
+
+			tmp = pit_update_counter(vatpit, c, false);
+			if (c->frbyte)
+				tmp >>= 8;
+			tmp &= 0xff;
+			vmexit->u.inout.eax = tmp;
+			c->frbyte ^= 1;
+		}  else
+			vmexit->u.inout.eax = c->ol[--c->olbyte];
+	} else {
+		c->cr[c->crbyte++] = vmexit->u.inout.eax;
+		if (c->crbyte == 2) {
+			c->frbyte = 0;
+			c->crbyte = 0;
+			c->initial = c->cr[0] | (uint16_t)c->cr[1] << 8;
+			c->now_sbt = sbinuptime();
+			/* Start an interval timer for channel 0 */
+			if (port == TIMER_CNTR0) {
+				c->callout_sbt = c->now_sbt;
+				pit_timer_start_cntr0(vatpit);
+			}
+			if (c->initial == 0)
+				c->initial = 0xffff;
+		}
+	}
+	VATPIT_UNLOCK(vatpit);
+
+	return (0);
+}
+
+struct vatpit *
+vatpit_init(struct vm *vm)
+{
+	struct vatpit *vatpit;
+	struct bintime bt;
+	struct vatpit_callout_arg *arg;
+	int i;
+
+	vatpit = malloc(sizeof(struct vatpit), M_VATPIT, M_WAITOK | M_ZERO);
+	vatpit->vm = vm;
+
+	mtx_init(&vatpit->mtx, "vatpit lock", NULL, MTX_SPIN);
+
+	FREQ2BT(PIT_8254_FREQ, &bt);
+	vatpit->freq_sbt = bttosbt(bt);
+
+	for (i = 0; i < 3; i++) {
+		callout_init(&vatpit->channel[i].callout, true);
+		arg = &vatpit->channel[i].callout_arg;
+		arg->vatpit = vatpit;
+		arg->channel_num = i;
+	}
+
+	return (vatpit);
+}
+
+void
+vatpit_cleanup(struct vatpit *vatpit)
+{
+	int i;
+
+	for (i = 0; i < 3; i++)
+		callout_drain(&vatpit->channel[i].callout);
+
+	free(vatpit, M_VATPIT);
+}
diff --git a/usr.sbin/bhyve/pit_8254.h b/sys/amd64/vmm/io/vatpit.h
index 61bd15d..4f30acf 100644
--- a/usr.sbin/bhyve/pit_8254.h
+++ b/sys/amd64/vmm/io/vatpit.h
@@ -1,4 +1,5 @@
 /*-
+ * Copyright (c) 2014 Tycho Nightingale <tycho.nightingale@pluribusnetworks.com>
  * Copyright (c) 2011 NetApp, Inc.
  * All rights reserved.
  *
@@ -26,20 +27,14 @@
  * $FreeBSD$
  */
 
-#ifndef _PIT_8254_H_
-#define	_PIT_8254_H_
+#ifndef _VATPIT_H_
+#define	_VATPIT_H_
 
-/*
- * Borrowed from amd64/include/timerreg.h because in that file it is
- * conditionally compiled for #ifdef _KERNEL only.
- */
+#include <machine/timerreg.h>
 
-#include <dev/ic/i8253reg.h>
+struct vatpit *vatpit_init(struct vm *vm);
+void vatpit_cleanup(struct vatpit *vatpit);
 
-#define	IO_TIMER1	0x40		/* 8253 Timer #1 */
-#define	TIMER_CNTR0	(IO_TIMER1 + TIMER_REG_CNTR0)
-#define	TIMER_CNTR1	(IO_TIMER1 + TIMER_REG_CNTR1)
-#define	TIMER_CNTR2	(IO_TIMER1 + TIMER_REG_CNTR2)
-#define	TIMER_MODE	(IO_TIMER1 + TIMER_REG_MODE)
+int vatpit_handler(void *vm, int vcpuid, struct vm_exit *vmexit);
 
-#endif	/* _PIT_8254_H_ */
+#endif	/* _VATPIT_H_ */
diff --git a/sys/amd64/vmm/vmm.c b/sys/amd64/vmm/vmm.c
index 3b78623..9d740d1 100644
--- a/sys/amd64/vmm/vmm.c
+++ b/sys/amd64/vmm/vmm.c
@@ -68,6 +68,7 @@ __FBSDID("$FreeBSD$");
 #include "vmm_mem.h"
 #include "vmm_util.h"
 #include "vatpic.h"
+#include "vatpit.h"
 #include "vhpet.h"
 #include "vioapic.h"
 #include "vlapic.h"
@@ -119,6 +120,7 @@ struct vm {
 	struct vhpet	*vhpet;		/* virtual HPET */
 	struct vioapic	*vioapic;	/* virtual ioapic */
 	struct vatpic	*vatpic;	/* virtual atpic */
+	struct vatpit	*vatpit;	/* virtual atpit */
 	struct vmspace	*vmspace;	/* guest's address space */
 	struct vcpu	vcpu[VM_MAXCPU];
 	int		num_mem_segs;
@@ -349,6 +351,7 @@ vm_create(const char *name, struct vm **retvm)
 	vm->vioapic = vioapic_init(vm);
 	vm->vhpet = vhpet_init(vm);
 	vm->vatpic = vatpic_init(vm);
+	vm->vatpit = vatpit_init(vm);
 
 	for (i = 0; i < VM_MAXCPU; i++) {
 		vcpu_init(vm, i);
@@ -381,6 +384,7 @@ vm_destroy(struct vm *vm)
 	if (vm->iommu != NULL)
 		iommu_destroy_domain(vm->iommu);
 
+	vatpit_cleanup(vm->vatpit);
 	vhpet_cleanup(vm->vhpet);
 	vatpic_cleanup(vm->vatpic);
 	vioapic_cleanup(vm->vioapic);
@@ -1740,3 +1744,9 @@ vm_atpic(struct vm *vm)
 {
 	return (vm->vatpic);
 }
+
+struct vatpit *
+vm_atpit(struct vm *vm)
+{
+	return (vm->vatpit);
+}
diff --git a/sys/amd64/vmm/vmm_ioport.c b/sys/amd64/vmm/vmm_ioport.c
index 7783dc2..1df916a 100644
--- a/sys/amd64/vmm/vmm_ioport.c
+++ b/sys/amd64/vmm/vmm_ioport.c
@@ -36,11 +36,16 @@ __FBSDID("$FreeBSD$");
 #include <machine/vmm.h>
 
 #include "vatpic.h"
+#include "vatpit.h"
 #include "vmm_ioport.h"
 
 #define	MAX_IOPORTS		1280
 
 ioport_handler_func_t ioport_handler[MAX_IOPORTS] = {
+	[TIMER_MODE] = vatpit_handler,
+	[TIMER_CNTR0] = vatpit_handler,
+	[TIMER_CNTR1] = vatpit_handler,
+	[TIMER_CNTR2] = vatpit_handler,
 	[IO_ICU1] = vatpic_master_handler,
 	[IO_ICU1 + ICU_IMR_OFFSET] = vatpic_master_handler,
 	[IO_ICU2] = vatpic_slave_handler,
diff --git a/sys/modules/vmm/Makefile b/sys/modules/vmm/Makefile
index 7a2b2df..76f9364 100644
--- a/sys/modules/vmm/Makefile
+++ b/sys/modules/vmm/Makefile
@@ -29,6 +29,7 @@ SRCS+=	vmm.c		\
 SRCS+=	iommu.c		\
 	ppt.c           \
 	vatpic.c	\
+	vatpit.c	\
 	vhpet.c		\
 	vioapic.c	\
 	vlapic.c
diff --git a/usr.sbin/bhyve/Makefile b/usr.sbin/bhyve/Makefile
index 98ead03..116fb60 100644
--- a/usr.sbin/bhyve/Makefile
+++ b/usr.sbin/bhyve/Makefile
@@ -27,7 +27,6 @@ SRCS=	\
 	pci_virtio_block.c	\
 	pci_virtio_net.c	\
 	pci_uart.c		\
-	pit_8254.c		\
 	pm.c			\
 	pmtmr.c			\
 	post.c			\
diff --git a/usr.sbin/bhyve/pit_8254.c b/usr.sbin/bhyve/pit_8254.c
deleted file mode 100644
index b45b100..0000000
--- a/usr.sbin/bhyve/pit_8254.c
+++ /dev/null
@@ -1,292 +0,0 @@
-/*-
- * Copyright (c) 2011 NetApp, Inc.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY NETAPP, INC ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL NETAPP, INC OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- *
- * $FreeBSD$
- */
-
-#include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
-
-#include <sys/types.h>
-#include <sys/time.h>
-#include <machine/vmm.h>
-
-#include <machine/clock.h>
-
-#include <assert.h>
-#include <stdio.h>
-#include <string.h>
-#include <unistd.h>
-
-#include <vmmapi.h>
-
-#include "acpi.h"
-#include "bhyverun.h"
-#include "inout.h"
-#include "mevent.h"
-#include "pci_lpc.h"
-#include "pit_8254.h"
-
-#define	TIMER_SEL_MASK		0xc0
-#define	TIMER_RW_MASK		0x30
-#define	TIMER_MODE_MASK		0x0f
-#define	TIMER_SEL_READBACK	0xc0
-
-#define	TIMER_DIV(freq, hz)	(((freq) + (hz) / 2) / (hz))
-
-#define	PIT_8254_FREQ		1193182
-static const int nsecs_per_tick = 1000000000 / PIT_8254_FREQ;
-
-struct counter {
-	struct vmctx	*ctx;
-	struct mevent	*tevp;	
-	struct timeval	tv;		/* uptime when counter was loaded */
-	int		mode;
-	uint16_t	initial;	/* initial counter value */
-	uint8_t		cr[2];
-	uint8_t		ol[2];
-	int		crbyte;
-	int		olbyte;
-	int		frbyte;
-};
-
-
-static void
-timevalfix(struct timeval *t1)
-{
-
-	if (t1->tv_usec < 0) {
-		t1->tv_sec--;
-		t1->tv_usec += 1000000;
-	}
-	if (t1->tv_usec >= 1000000) {
-		t1->tv_sec++;
-		t1->tv_usec -= 1000000;
-	}
-}
-
-static void
-timevalsub(struct timeval *t1, const struct timeval *t2)
-{
-
-	t1->tv_sec -= t2->tv_sec;
-	t1->tv_usec -= t2->tv_usec;
-	timevalfix(t1);
-}
-
-static uint64_t pit_mev_count;
-
-static void
-pit_mevent_cb(int fd, enum ev_type type, void *param)
-{
-	struct counter *c;
-
-	c = param;
-
-	pit_mev_count++;
-
-	vm_isa_pulse_irq(c->ctx, 0, 2);
-
-	/*
-	 * Delete the timer for one-shots
-	 */
-	if (c->mode != TIMER_RATEGEN) {
-		mevent_delete(c->tevp);
-		c->tevp = NULL;
-	}
-}
-
-static void
-pit_timer_start(struct vmctx *ctx, struct counter *c)
-{
-	int msecs;
-
-	if (c->initial != 0) {
-		msecs = c->initial * nsecs_per_tick / 1000000;
-		if (msecs == 0)
-			msecs = 1;
-
-		if (c->tevp == NULL)
-			c->tevp = mevent_add(msecs, EVF_TIMER, pit_mevent_cb,
-			    c);
-	}
-}
-
-static uint16_t
-pit_update_counter(struct counter *c, int latch)
-{
-	struct timeval tv2;
-	uint16_t lval;
-	uint64_t delta_nsecs, delta_ticks;
-
-	/* cannot latch a new value until the old one has been consumed */
-	if (latch && c->olbyte != 0)
-		return (0);
-
-	if (c->initial == 0 || c->initial == 1) {
-		/*
-		 * XXX the program that runs the VM can be stopped and
-		 * restarted at any time. This means that state that was
-		 * created by the guest is destroyed between invocations
-		 * of the program.
-		 *
-		 * If the counter's initial value is not programmed we
-		 * assume a value that would be set to generate 100
-		 * interrupts per second.
-		 */
-		c->initial = TIMER_DIV(PIT_8254_FREQ, 100);
-		gettimeofday(&c->tv, NULL);
-	}
-	
-	(void)gettimeofday(&tv2, NULL);
-	timevalsub(&tv2, &c->tv);
-	delta_nsecs = tv2.tv_sec * 1000000000 + tv2.tv_usec * 1000;
-	delta_ticks = delta_nsecs / nsecs_per_tick;
-
-	lval = c->initial - delta_ticks % c->initial;
-
-	if (latch) {
-		c->olbyte = 2;
-		c->ol[1] = lval;		/* LSB */
-		c->ol[0] = lval >> 8;		/* MSB */
-	}
-
-	return (lval);
-}
-
-static int
-pit_8254_handler(struct vmctx *ctx, int vcpu, int in, int port, int bytes,
-		 uint32_t *eax, void *arg)
-{
-	int sel, rw, mode;
-	uint8_t val;
-	struct counter *c;
-
-	static struct counter counter[3];
-
-	if (bytes != 1)
-		return (-1);
-
-	val = *eax;
-
-	if (port == TIMER_MODE) {
-		assert(in == 0);
-		sel = val & TIMER_SEL_MASK;
-		rw = val & TIMER_RW_MASK;
-		mode = val & TIMER_MODE_MASK;
-
-		if (sel == TIMER_SEL_READBACK)
-			return (-1);
-		if (rw != TIMER_LATCH && rw != TIMER_16BIT)
-			return (-1);
-
-		if (rw != TIMER_LATCH) {
-			/*
-			 * Counter mode is not affected when issuing a
-			 * latch command.
-			 */
-			if (mode != TIMER_INTTC &&
-			    mode != TIMER_RATEGEN &&
-			    mode != TIMER_SQWAVE &&
-			    mode != TIMER_SWSTROBE)
-				return (-1);
-		}
-		
-		c = &counter[sel >> 6];
-		c->ctx = ctx;
-		if (rw == TIMER_LATCH)
-			pit_update_counter(c, 1);
-		else {
-			c->mode = mode;
-			c->olbyte = 0;	/* reset latch after reprogramming */
-		}
-		
-		return (0);
-	}
-
-	/* counter ports */
-	assert(port >= TIMER_CNTR0 && port <= TIMER_CNTR2);
-	c = &counter[port - TIMER_CNTR0];
-
-	if (in) {
-		/*
-		 * The spec says that once the output latch is completely
-		 * read it should revert to "following" the counter. Use
-		 * the free running counter for this case (i.e. Linux
-		 * TSC calibration). Assuming the access mode is 16-bit,
-		 * toggle the MSB/LSB bit on each read.
-		 */
-		if (c->olbyte == 0) {
-			uint16_t tmp;
-
-			tmp = pit_update_counter(c, 0);
-			if (c->frbyte)
-				tmp >>= 8;
-			tmp &= 0xff;
-			*eax = tmp;
-			c->frbyte ^= 1;
-		}  else
-			*eax = c->ol[--c->olbyte];
-	} else {
-		c->cr[c->crbyte++] = *eax;
-		if (c->crbyte == 2) {
-			c->frbyte = 0;
-			c->crbyte = 0;
-			c->initial = c->cr[0] | (uint16_t)c->cr[1] << 8;
-			/* Start an interval timer for counter 0 */
-			if (port == 0x40)
-				pit_timer_start(ctx, c);
-			if (c->initial == 0)
-				c->initial = 0xffff;
-			gettimeofday(&c->tv, NULL);
-		}
-	}
-
-	return (0);
-}
-
-INOUT_PORT(8254, TIMER_MODE, IOPORT_F_OUT, pit_8254_handler);
-INOUT_PORT(8254, TIMER_CNTR0, IOPORT_F_INOUT, pit_8254_handler);
-INOUT_PORT(8254, TIMER_CNTR1, IOPORT_F_INOUT, pit_8254_handler);
-INOUT_PORT(8254, TIMER_CNTR2, IOPORT_F_INOUT, pit_8254_handler);
-
-static void
-pit_dsdt(void)
-{
-
-	dsdt_line("");
-	dsdt_line("Device (TIMR)");
-	dsdt_line("{");
-	dsdt_line("  Name (_HID, EisaId (\"PNP0100\"))");
-	dsdt_line("  Name (_CRS, ResourceTemplate ()");
-	dsdt_line("  {");
-	dsdt_indent(2);
-	dsdt_fixed_ioport(IO_TIMER1, 4);
-	dsdt_fixed_irq(0);
-	dsdt_unindent(2);
-	dsdt_line("  })");
-	dsdt_line("}");
-}
-LPC_DSDT(pit_dsdt);