diff --git a/Makefile.objs b/Makefile.objs
index 808de6a..3372d9b 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -302,6 +302,8 @@ hw-obj-$(CONFIG_DP8393X) += dp8393x.o
 hw-obj-$(CONFIG_DS1225Y) += ds1225y.o
 hw-obj-$(CONFIG_MIPSNET) += mipsnet.o
 
+hw-obj-y += qtest.o
+
 # Sound
 sound-obj-y =
 sound-obj-$(CONFIG_SB16) += sb16.o
diff --git a/cpu-exec.c b/cpu-exec.c
index 2c2d24e..d476616 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -21,6 +21,7 @@
 #include "disas.h"
 #include "tcg.h"
 #include "qemu-barrier.h"
+#include "qtest.h"
 
 int tb_invalidated_flag;
 
diff --git a/cpus.c b/cpus.c
index f45a438..c77e649 100644
--- a/cpus.c
+++ b/cpus.c
@@ -740,6 +740,48 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
     return NULL;
 }
 
+static void *qemu_dummy_cpu_thread_fn(void *arg)
+{
+#ifdef _WIN32
+    fprintf(stderr, "qtest is not supported under Windows\n");
+    exit(1);
+#else
+    CPUState *env = arg;
+    sigset_t waitset;
+    int r;
+
+    qemu_mutex_lock_iothread();
+    qemu_thread_get_self(env->thread);
+    env->thread_id = qemu_get_thread_id();
+
+    sigemptyset(&waitset);
+    sigaddset(&waitset, SIG_IPI);
+
+    /* signal CPU creation */
+    env->created = 1;
+    qemu_cond_signal(&qemu_cpu_cond);
+
+    cpu_single_env = env;
+    while (1) {
+        cpu_single_env = NULL;
+        qemu_mutex_unlock_iothread();
+        do {
+            int sig;
+            r = sigwait(&waitset, &sig);
+        } while (r == -1 && (errno == EAGAIN || errno == EINTR));
+        if (r == -1) {
+            perror("sigwait");
+            exit(1);
+        }
+        qemu_mutex_lock_iothread();
+        cpu_single_env = env;
+        qemu_wait_io_event_common(env);
+    }
+
+    return NULL; 
+#endif
+}
+
 static void tcg_exec_all(void);
 
 static void *qemu_tcg_cpu_thread_fn(void *arg)
@@ -797,7 +839,7 @@ void qemu_cpu_kick(void *_env)
     CPUState *env = _env;
 
     qemu_cond_broadcast(env->halt_cond);
-    if (kvm_enabled() && !env->thread_kicked) {
+    if (!tcg_enabled() && !env->thread_kicked) {
         qemu_cpu_kick_thread(env);
         env->thread_kicked = true;
     }
@@ -826,7 +868,7 @@ int qemu_cpu_is_self(void *_env)
 
 void qemu_mutex_lock_iothread(void)
 {
-    if (kvm_enabled()) {
+    if (!tcg_enabled()) {
         qemu_mutex_lock(&qemu_global_mutex);
     } else {
         iothread_requesting_mutex = true;
@@ -929,6 +971,18 @@ static void qemu_kvm_start_vcpu(CPUState *env)
     }
 }
 
+static void qemu_dummy_start_vcpu(CPUState *env)
+{
+    env->thread = g_malloc0(sizeof(QemuThread));
+    env->halt_cond = g_malloc0(sizeof(QemuCond));
+    qemu_cond_init(env->halt_cond);
+    qemu_thread_create(env->thread, qemu_dummy_cpu_thread_fn, env,
+                       QEMU_THREAD_JOINABLE);
+    while (env->created == 0) {
+        qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
+    }
+}
+
 void qemu_init_vcpu(void *_env)
 {
     CPUState *env = _env;
@@ -938,8 +992,10 @@ void qemu_init_vcpu(void *_env)
     env->stopped = 1;
     if (kvm_enabled()) {
         qemu_kvm_start_vcpu(env);
-    } else {
+    } else if (tcg_enabled()) {
         qemu_tcg_init_vcpu(env);
+    } else {
+        qemu_dummy_start_vcpu(env);
     }
 }
 
diff --git a/qemu-options.hx b/qemu-options.hx
index b129996..3dca2dc 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2698,6 +2698,14 @@ the @var{simple} tracing backend.
 @end table
 ETEXI
 
+DEF("qtest", HAS_ARG, QEMU_OPTION_qtest,
+    "-qtest CHR      specify tracing options\n",
+    QEMU_ARCH_ALL)
+
+DEF("qtest-log", HAS_ARG, QEMU_OPTION_qtest_log,
+    "-qtest-log LOG  specify tracing options\n",
+    QEMU_ARCH_ALL)
+
 HXCOMM This is the last statement. Insert new options before this line!
 STEXI
 @end table
diff --git a/qtest.c b/qtest.c
new file mode 100644
index 0000000..c2fbf50
--- /dev/null
+++ b/qtest.c
@@ -0,0 +1,359 @@
+/*
+ * Test Server
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qtest.h"
+#include "qemu-char.h"
+#include "ioport.h"
+#include "memory.h"
+#include "hw/irq.h"
+#include "sysemu.h"
+
+#define MAX_IRQ 256
+
+const char *qtest_chrdev;
+const char *qtest_log;
+int qtest_allowed = 0;
+
+static FILE *qtest_log_fp;
+static CharDriverState *qtest_chr;
+static GString *inbuf;
+static int irq_levels[MAX_IRQ];
+static struct timeval start_time;
+static bool qtest_opened;
+
+#define FMT_timeval "%" PRId64 ".%06" PRId64
+
+/**
+ * QTest Protocol
+ *
+ * Line based protocol, request/response based.  Server can send async messages
+ * so clients should always handle many async messages before the response
+ * comes in.
+ *
+ * Valid requests
+ *
+ *  > outb ADDR VALUE
+ *  < OK
+ *
+ *  > outw ADDR VALUE
+ *  < OK
+ *
+ *  > outl ADDR VALUE
+ *  < OK
+ *
+ *  > inb ADDR
+ *  < OK VALUE
+ *
+ *  > inw ADDR
+ *  < OK VALUE
+ *
+ *  > inl ADDR
+ *  < OK VALUE
+ *
+ *  > read ADDR SIZE
+ *  < OK DATA
+ *
+ *  > write ADDR SIZE DATA
+ *  < OK
+ *
+ * Valid async messages:
+ *
+ *  IRQ raise NUM
+ *  IRQ lower NUM
+ *
+ * ADDR, SIZE, VALUE are all integers parsed with strtoul() with a base of 0.
+ *
+ * DATA is an arbitrarily long hex number prefixed with '0x'.  If it's smaller
+ * than the expected size, the value will be zero filled at the end of the data
+ * sequence.
+ *
+ * NUM is an IRQ number.
+ */
+
+static int hex2nib(char ch)
+{
+    if (ch >= '0' && ch <= '9') {
+        return ch - '0';
+    } else if (ch >= 'a' && ch <= 'f') {
+        return 10 + (ch - 'a');
+    } else if (ch >= 'A' && ch <= 'F') {
+        return 10 + (ch - 'a');
+    } else {
+        return -1;
+    }
+}
+
+static void qtest_get_time(struct timeval *tv)
+{
+    gettimeofday(tv, NULL);
+    tv->tv_sec -= start_time.tv_sec;
+    tv->tv_usec -= start_time.tv_usec;
+    if (tv->tv_usec < 0) {
+        tv->tv_usec += 1000000;
+        tv->tv_sec -= 1;
+    }
+}
+
+static void qtest_send_prefix(CharDriverState *chr)
+{
+    struct timeval tv;
+
+    if (!qtest_log_fp || !qtest_opened) {
+        return;
+    }
+
+    qtest_get_time(&tv);
+    fprintf(qtest_log_fp, "[S +" FMT_timeval "] ",
+            tv.tv_sec, tv.tv_usec);
+}
+
+static void qtest_send(CharDriverState *chr, const char *fmt, ...)
+{
+    va_list ap;
+    char buffer[1024];
+    size_t len;
+
+    va_start(ap, fmt);
+    len = vsnprintf(buffer, sizeof(buffer), fmt, ap);
+    va_end(ap);
+
+    qemu_chr_fe_write(chr, (uint8_t *)buffer, len);
+    if (qtest_log_fp && qtest_opened) {
+        fprintf(qtest_log_fp, "%s", buffer);
+    }
+}
+
+static void qtest_process_command(CharDriverState *chr, gchar **words)
+{
+    const gchar *command;
+
+    g_assert(words);
+
+    command = words[0];
+
+    if (qtest_log_fp) {
+        struct timeval tv;
+        int i;
+
+        qtest_get_time(&tv);
+        fprintf(qtest_log_fp, "[R +" FMT_timeval "]",
+                tv.tv_sec, tv.tv_usec);
+        for (i = 0; words[i]; i++) {
+            fprintf(qtest_log_fp, " %s", words[i]);
+        }
+        fprintf(qtest_log_fp, "\n");
+    }
+
+    g_assert(command);
+    if (strcmp(words[0], "outb") == 0 ||
+        strcmp(words[0], "outw") == 0 ||
+        strcmp(words[0], "outl") == 0) {
+        uint16_t addr;
+        uint32_t value;
+
+        g_assert(words[1] && words[2]);
+        addr = strtol(words[1], NULL, 0);
+        value = strtol(words[2], NULL, 0);
+
+        if (words[0][3] == 'b') {
+            cpu_outb(addr, value);
+        } else if (words[0][3] == 'w') {
+            cpu_outw(addr, value);
+        } else if (words[0][3] == 'l') {
+            cpu_outl(addr, value);
+        }
+        qtest_send_prefix(chr);
+        qtest_send(chr, "OK\n");
+    } else if (strcmp(words[0], "inb") == 0 ||
+        strcmp(words[0], "inw") == 0 ||
+        strcmp(words[0], "inl") == 0) {
+        uint16_t addr;
+        uint32_t value = -1U;
+
+        g_assert(words[1]);
+        addr = strtol(words[1], NULL, 0);
+
+        if (words[0][2] == 'b') {
+            value = cpu_inb(addr);
+        } else if (words[0][2] == 'w') {
+            value = cpu_inw(addr);
+        } else if (words[0][2] == 'l') {
+            value = cpu_inl(addr);
+        }
+        qtest_send_prefix(chr);
+        qtest_send(chr, "OK 0x%04x\n", value);
+    } else if (strcmp(words[0], "read") == 0) {
+        uint64_t addr, len, i;
+        uint8_t *data;
+
+        g_assert(words[1] && words[2]);
+        addr = strtoul(words[1], NULL, 0);
+        len = strtoul(words[2], NULL, 0);
+
+        data = g_malloc(len);
+        cpu_physical_memory_read(addr, data, len);
+
+        qtest_send_prefix(chr);
+        qtest_send(chr, "OK 0x");
+        for (i = 0; i < len; i++) {
+            qtest_send(chr, "%02x", data[i]);
+        }
+        qtest_send(chr, "\n");
+
+        g_free(data);
+    } else if (strcmp(words[0], "write") == 0) {
+        uint64_t addr, len, i;
+        uint8_t *data;
+        size_t data_len;
+
+        g_assert(words[1] && words[2] && words[3]);
+        addr = strtoul(words[1], NULL, 0);
+        len = strtoul(words[2], NULL, 0);
+
+        data_len = strlen(words[3]);
+        if (data_len < 3) {
+            qtest_send(chr, "ERR invalid argument size\n");
+            return;
+        }
+
+        data = g_malloc(len);
+        for (i = 0; i < len; i++) {
+            if ((i * 2 + 4) <= data_len) {
+                data[i] = hex2nib(words[3][i * 2 + 2]) << 4;
+                data[i] |= hex2nib(words[3][i * 2 + 3]);
+            } else {
+                data[i] = 0;
+            }
+        }
+        cpu_physical_memory_write(addr, data, len);
+        g_free(data);
+
+        qtest_send_prefix(chr);
+        qtest_send(chr, "OK\n");
+    } else {
+        qtest_send_prefix(chr);
+        qtest_send(chr, "FAIL Unknown command `%s'\n", words[0]);
+    }
+}
+
+static void qtest_process_inbuf(CharDriverState *chr, GString *inbuf)
+{
+    char *end;
+
+    while ((end = strchr(inbuf->str, '\n')) != NULL) {
+        size_t offset;
+        GString *cmd;
+        gchar **words;
+
+        offset = end - inbuf->str;
+
+        cmd = g_string_new_len(inbuf->str, offset);
+        g_string_erase(inbuf, 0, offset + 1);
+
+        words = g_strsplit(cmd->str, " ", 0);
+        qtest_process_command(chr, words);
+        g_strfreev(words);
+
+        g_string_free(cmd, TRUE);
+    }
+}
+
+static void qtest_read(void *opaque, const uint8_t *buf, int size)
+{
+    CharDriverState *chr = opaque;
+
+    g_string_append_len(inbuf, (const gchar *)buf, size);
+    qtest_process_inbuf(chr, inbuf);
+}
+
+static int qtest_can_read(void *opaque)
+{
+    return 1024;
+}
+
+static void qtest_event(void *opaque, int event)
+{
+    int i;
+
+    switch (event) {
+    case CHR_EVENT_OPENED:
+        qemu_system_reset(false);
+        for (i = 0; i < ARRAY_SIZE(irq_levels); i++) {
+            irq_levels[i] = 0;
+        }
+        gettimeofday(&start_time, NULL);
+        qtest_opened = true;
+        if (qtest_log_fp) {
+            fprintf(qtest_log_fp, "[I " FMT_timeval "] OPENED\n",
+                    start_time.tv_sec, start_time.tv_usec);
+        }
+        break;
+    case CHR_EVENT_CLOSED:
+        qtest_opened = false;
+        if (qtest_log_fp) {
+            struct timeval tv;
+            qtest_get_time(&tv);
+            fprintf(qtest_log_fp, "[I +" FMT_timeval "] CLOSED\n",
+                    tv.tv_sec, tv.tv_usec);
+        }
+        break;
+    default:
+        break;
+    }
+}
+
+static void qtest_set_irq(void *opaque, int irq, int level)
+{
+    CharDriverState *chr = qtest_chr;
+    bool changed;
+
+    changed = (irq_levels[irq] != level);
+    irq_levels[irq] = level;
+
+    if (changed) {
+        qtest_send_prefix(chr);
+        qtest_send(chr, "IRQ %s %d\n",
+                   level ? "raise" : "lower", irq);
+    }
+}
+
+qemu_irq *qtest_interrupt_controller_init(void)
+{
+    return qemu_allocate_irqs(qtest_set_irq, NULL, MAX_IRQ);
+}
+
+int qtest_init(void)
+{
+    CharDriverState *chr;
+
+    g_assert(qtest_chrdev != NULL);
+
+    chr = qemu_chr_new("qtest", qtest_chrdev, NULL);
+
+    qemu_chr_add_handlers(chr, qtest_can_read, qtest_read, qtest_event, chr);
+    qemu_chr_fe_set_echo(chr, true);
+
+    inbuf = g_string_new("");
+
+    if (qtest_log) {
+        if (strcmp(qtest_log, "none") != 0) {
+            qtest_log_fp = fopen(qtest_log, "w+");
+        }
+    } else {
+        qtest_log_fp = stderr;
+    }
+
+    qtest_chr = chr;
+
+    return 0;
+}
diff --git a/qtest.h b/qtest.h
new file mode 100644
index 0000000..f0e1377
--- /dev/null
+++ b/qtest.h
@@ -0,0 +1,37 @@
+/*
+ * Test Server
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef QTEST_H
+#define QTEST_H
+
+#include "qemu-common.h"
+
+extern int qtest_allowed;
+extern const char *qtest_chrdev;
+extern const char *qtest_log;
+
+static inline bool qtest_enabled(void)
+{
+    return qtest_allowed;
+}
+
+static inline int qtest_available(void)
+{
+    return 1;
+}
+
+int qtest_init(void);
+
+qemu_irq *qtest_interrupt_controller_init(void);
+
+#endif
diff --git a/vl.c b/vl.c
index 1d4c350..1473016 100644
--- a/vl.c
+++ b/vl.c
@@ -152,6 +152,7 @@ int main(int argc, char **argv)
 #ifdef CONFIG_VIRTFS
 #include "fsdev/qemu-fsdev.h"
 #endif
+#include "qtest.h"
 
 #include "disas.h"
 
@@ -2097,6 +2098,7 @@ static struct {
     { "tcg", "tcg", tcg_available, tcg_init, &tcg_allowed },
     { "xen", "Xen", xen_available, xen_init, &xen_allowed },
     { "kvm", "KVM", kvm_available, kvm_init, &kvm_allowed },
+    { "qtest", "QTest", qtest_available, qtest_init, &qtest_allowed },
 };
 
 static int configure_accelerator(void)
@@ -3180,6 +3182,12 @@ int main(int argc, char **argv, char **envp)
                     fclose(fp);
                     break;
                 }
+            case QEMU_OPTION_qtest:
+                qtest_chrdev = optarg;
+                break;
+            case QEMU_OPTION_qtest_log:
+                qtest_log = optarg;
+                break;
             default:
                 os_parse_cmd_args(popt->index, optarg);
             }
