@@ -131,7 +131,7 @@ endif #CONFIG_BSD_USER
#########################################################
# System emulator target
ifdef CONFIG_SOFTMMU
-obj-y += arch_init.o cpus.o monitor.o gdbstub.o balloon.o ioport.o numa.o
+obj-y += arch_init.o qqq.o cpus.o monitor.o gdbstub.o balloon.o ioport.o numa.o
obj-y += qtest.o bootdevice.o
obj-y += hw/
obj-$(CONFIG_KVM) += kvm-all.o
@@ -44,6 +44,8 @@
#include "hw/nmi.h"
#include "sysemu/replay.h"
+#include "qqq.h"
+
#ifndef _WIN32
#include "qemu/compatfd.h"
#endif
@@ -995,10 +997,17 @@ static void qemu_wait_io_event_common(CPUState *cpu)
static void qemu_tcg_wait_io_event(CPUState *cpu)
{
while (all_cpu_threads_idle()) {
- /* Start accounting real time to the virtual clock if the CPUs
+ /* Start accounting real time to the virtual clock if the CPUs
are idle. */
qemu_clock_warp(QEMU_CLOCK_VIRTUAL);
- qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex);
+ /* If qqq is running then this wait must timeout so that the
+ * simulation does not become stuck when the cpu idles */
+ if (qqq_enabled()) {
+ qemu_cond_wait_timeout_ns(cpu->halt_cond,
+ &qemu_global_mutex, 10000);
+ } else {
+ qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex);
+ }
}
while (iothread_requesting_mutex) {
new file mode 100644
@@ -0,0 +1,61 @@
+= Synchronizing the virtual clock with an external source =
+
+QEMU has a protocol for synchronizing its virtual clock
+with the clock of a simulator in which QEMU is embedded
+as a component. This options is enabled with the -qqq
+argument, and it should generally be accompanied by the
+following additional command line arguments:
+
+-icount 1,sleep=off -rtc clock=vm
+
+The -qqq argument is used to supply file descriptors
+for two Unix pipes. The read pipe is used by QEMU to
+receive synchronization data from the external simulator.
+The write pipe is used by QEMU to supply synchronization
+data to the external emulator. The typical procedure for
+launching QEMU in is synchronization mode has three steps:
+
+(1) Create two pairs of pipes with the Linux pipe function.
+ The code segment that does this might look like
+
+ int pipefd1[2];
+ int pipefd2[2];
+ pipe(pipefd1);
+ pipe(pipefd2);
+
+(2) Fork QEMU with the appropriate command line arguments.
+ The -qqq part of the argument will look something like
+
+ -qqq write=pipefd1[1],read=pipefd2[0]
+
+(3) After forking QEMU, close pipefd1[1] and pipefd2[0].
+ Retain the other pair of pipes for communicating
+ with QEMU.
+
+The synchronization protocol is very simple. To start, the
+external simulator writes an integer to its write pipe with
+the amount of time in microseconds that QEMU is allowed to
+advance. The code segment that does this might look like:
+
+ int ta = 1000; // Advance by 1 millisecond
+ write(pipefd2[1],&ta,sizeof(int));
+
+The external simulator can then advance its clock by this
+same amount. During this time, QEMU and the external simulator
+will be executing in parallel. When the external simulator
+completes its time advance, it waits for QEMU by reading from
+its read pipe. The value read will be the actual number of
+virtual microseconds by which QEMU has advanced its virtual clock.
+This will be greater than or equal to the requested advance.
+The code that does this might look like:
+
+ read(pipefd1[0],&ta,sizeof(int));
+
+These steps are repeated until either (1) the external simulator
+closes its pipes thereby causing QEMU to terminate or (2) QEMU
+stops executing (e.g., if the emulated computer is shutdown) and
+causes SIGPIPE to be generated by the closing of its pipes.
+
+You can find an example of a simulator using this protocol in
+the adevs simulation package at http://sourceforge.net/projects/adevs/
+
@@ -36,6 +36,17 @@ void qemu_cond_destroy(QemuCond *cond);
void qemu_cond_signal(QemuCond *cond);
void qemu_cond_broadcast(QemuCond *cond);
void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex);
+/* This defaults to qemu_cond_wait() on Windows */
+#ifndef _WIN32
+void qemu_cond_wait_timeout_ns(QemuCond *cond, QemuMutex *mutex,
+ int64_t timeout_ns);
+#else
+void qemu_cond_wait_timeout_ns(QemuCond *cond, QemuMutex *mutex,
+ int64_t timeout_ns)
+{
+ qemu_cond_wait(cond, mutex);
+}
+#endif
void qemu_sem_init(QemuSemaphore *sem, int init);
void qemu_sem_post(QemuSemaphore *sem);
@@ -3225,6 +3225,23 @@ many timer interrupts were not processed by the Windows guest and will
re-inject them.
ETEXI
+DEF("qqq", HAS_ARG, QEMU_OPTION_qqq, \
+ "-qqq read=fd,write=fd\n" \
+ " enable synchronization of the virtual clock \n" \
+ " with an external simulation clock\n", QEMU_ARCH_ALL)
+STEXI
+@item -qqq read=@var{fd0},write=@var{fd1}
+@findex -qqq
+Qemu will use the supplied pipes to synchronize its virtual clock with
+an external simulation clock. This requires the option
+'icount 1,sleep=off'. Qemu will wait until a time slice size in
+microseconds is supplied on the read pipe. Then it will execute for at
+least that number of virtual microseconds before writing the actual
+virtual time that has elapsed in microseconds to the write pipe. This
+cycle will repeat until a zero is elaspsed time is requested, which
+will cause qemu to exit.
+ETEXI
+
DEF("icount", HAS_ARG, QEMU_OPTION_icount, \
"-icount [shift=N|auto][,align=on|off][,sleep=no,rr=record|replay,rrfile=<filename>]\n" \
" enable virtual instruction counter with 2^N clock ticks per\n" \
new file mode 100644
@@ -0,0 +1,98 @@
+
+#include "qemu/osdep.h"
+#include "qemu/timer.h"
+#include "qqq.h"
+
+/* This is a Linux only feature */
+
+#ifndef _WIN32
+
+#include <unistd.h>
+#include <assert.h>
+
+static int read_fd = -1, write_fd = -1;
+static int64_t t;
+static QEMUTimer *sync_timer;
+
+static void cleanup_and_exit(void)
+{
+ close(read_fd);
+ close(write_fd);
+ exit(0);
+}
+
+static void write_mem_value(int val)
+{
+ if (write(write_fd, &val, sizeof(int)) != sizeof(int)) {
+ /* If the pipe is no good, then assume this is an
+ * indication that we should exit.
+ */
+ cleanup_and_exit();
+ }
+}
+
+static int read_mem_value(void)
+{
+ int tmp;
+ if (read(read_fd, &tmp, sizeof(int)) != sizeof(int)) {
+ /* If the pipe is no good, then assume this is an
+ * indication that we should exit.
+ */
+ cleanup_and_exit();
+ }
+ return tmp;
+}
+
+static void schedule_next_event(void)
+{
+ int time_advance;
+ /* Get the time advance allowed by the simulator. */
+ time_advance = read_mem_value();
+ /* Schedule the next synchronization point */
+ timer_mod(sync_timer, t + time_advance);
+}
+
+static void sync_func(void *data)
+{
+ /* Report the actual elapsed time. */
+ int64_t tnow = qemu_clock_get_us(QEMU_CLOCK_VIRTUAL);
+ int usecs = tnow - t;
+ write_mem_value(usecs);
+ /* Update our time of last event */
+ t = tnow;
+ /* Schedule the next event */
+ schedule_next_event();
+}
+
+bool qqq_enabled(void)
+{
+ return (read_fd > 0 && write_fd > 0);
+}
+
+void setup_qqq(QemuOpts *opts)
+{
+ /* Initialize the simulation clock */
+ t = 0;
+ /* Get the communication pipes */
+ read_fd = qemu_opt_get_number(opts, "read", 0);
+ write_fd = qemu_opt_get_number(opts, "write", 0);
+ /* Start the timer to ensure time warps advance the clock */
+ sync_timer = timer_new_us(QEMU_CLOCK_VIRTUAL, sync_func, NULL);
+ /* Get the time advance that is requested by the simulation */
+ schedule_next_event();
+}
+
+#else
+
+bool qqq_enabled(void)
+{
+ return false;
+}
+
+void setup_qqq(QemuOpts *opts)
+{
+ fprintf(stderr, "-qqq is not supported on Windows, exiting\n");
+ exit(0);
+}
+
+#endif
new file mode 100644
@@ -0,0 +1,39 @@
+/*
+ * This work is licensed under the terms of the GNU GPL
+ * version 2. Seethe COPYING file in the top-level directory.
+ *
+ * A module for pacing the rate of advance of the computer
+ * clock in reference to an external simulation clock. The
+ * basic approach used here is adapted from QBox from Green
+ * Socs. The mode of operation is as follows:
+ *
+ * The simulator uses pipes to exchange time advance data.
+ * The external simulator starts the exchange by forking a
+ * QEMU process and passing is descriptors for a read and
+ * write pipe. Then the external simulator writes an integer
+ * (native endian) to the pipe to indicate the number of
+ * microseconds that QEMU should advance. QEMU advances its
+ * virtual clock by this amount and writes to its write pipe
+ * the actual number of microseconds that have advanced.
+ * This process continues until a pipe on either side is
+ * closed, which will either cause QEMU to exit (if the
+ * external simulator closes a pipe) or raise SIGPIPE in the
+ * external simulator (if QEMU closes a pipe).
+ *
+ * Authors:
+ * James Nutaro <nutaro@gmail.com>
+ *
+ */
+#ifndef QQQ_H
+#define QQQ_H
+
+#include "qemu/osdep.h"
+#include "qemu-options.h"
+
+void setup_qqq(QemuOpts *opts);
+/* Returns true if qqq is enabled and false otherwise.
+ * It will be enabled only if setup_qqq() is able to
+ * attach to the shared memory segment. */
+bool qqq_enabled(void);
+
+#endif
@@ -134,6 +134,22 @@ void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
error_exit(err, __func__);
}
+void qemu_cond_wait_timeout_ns(QemuCond *cond, QemuMutex *mutex,
+ int64_t timeout_ns)
+{
+ static const long ns_sec = 1000000000;
+ struct timeval tv;
+ struct timespec ts;
+ int err;
+ gettimeofday(&tv, NULL);
+ ts.tv_sec = tv.tv_sec + (timeout_ns + (tv.tv_usec * 1000)) / ns_sec;
+ ts.tv_nsec = (timeout_ns + (tv.tv_usec * 1000)) % ns_sec;
+ err = pthread_cond_timedwait(&cond->cond, &mutex->lock, &ts);
+ if (err != 0 && err != ETIMEDOUT) {
+ error_exit(err, __func__);
+ }
+}
+
void qemu_sem_init(QemuSemaphore *sem, int init)
{
int rc;
@@ -125,6 +125,8 @@ int main(int argc, char **argv)
#include "sysemu/replay.h"
#include "qapi/qmp/qerror.h"
+#include "qqq.h"
+
#define MAX_VIRTIO_CONSOLES 1
#define MAX_SCLP_CONSOLES 1
@@ -486,6 +488,23 @@ static QemuOptsList qemu_icount_opts = {
},
};
+static QemuOptsList qemu_qqq_opts = {
+ .name = "qqq",
+ .implied_opt_name = "",
+ .merge_lists = true,
+ .head = QTAILQ_HEAD_INITIALIZER(qemu_qqq_opts.head),
+ .desc = {
+ {
+ .name = "read",
+ .type = QEMU_OPT_NUMBER,
+ }, {
+ .name = "write",
+ .type = QEMU_OPT_NUMBER,
+ },
+ { /* end of list */ }
+ },
+};
+
static QemuOptsList qemu_semihosting_config_opts = {
.name = "semihosting-config",
.implied_opt_name = "enable",
@@ -2969,7 +2988,8 @@ int main(int argc, char **argv, char **envp)
const char *boot_once = NULL;
DisplayState *ds;
int cyls, heads, secs, translation;
- QemuOpts *hda_opts = NULL, *opts, *machine_opts, *icount_opts = NULL;
+ QemuOpts *hda_opts = NULL, *opts, *machine_opts,
+ *icount_opts = NULL, *qqq_opts = NULL;
QemuOptsList *olist;
int optind;
const char *optarg;
@@ -3031,6 +3051,7 @@ int main(int argc, char **argv, char **envp)
qemu_add_opts(&qemu_name_opts);
qemu_add_opts(&qemu_numa_opts);
qemu_add_opts(&qemu_icount_opts);
+ qemu_add_opts(&qemu_qqq_opts);
qemu_add_opts(&qemu_semihosting_config_opts);
qemu_add_opts(&qemu_fw_cfg_opts);
@@ -3868,6 +3889,13 @@ int main(int argc, char **argv, char **envp)
exit(1);
}
break;
+ case QEMU_OPTION_qqq:
+ qqq_opts = qemu_opts_parse_noisily(qemu_find_opts("qqq"),
+ optarg, true);
+ if (!qqq_opts) {
+ exit(1);
+ }
+ break;
case QEMU_OPTION_incoming:
if (!incoming) {
runstate_set(RUN_STATE_INMIGRATE);
@@ -4385,6 +4413,11 @@ int main(int argc, char **argv, char **envp)
/* spice needs the timers to be initialized by this point */
qemu_spice_init();
#endif
+ /* try to setup the qqq interface for syncing advance of the
+ * virtual clock with an external simulator */
+ if (qqq_opts && icount_opts) {
+ setup_qqq(qqq_opts);
+ }
cpu_ticks_init();
if (icount_opts) {
This patch adds an interface for pacing the execution of QEMU to match an external simulation clock. Its aim is to permit QEMU to be used as a module within a larger simulation system. Signed-off-by: James J. Nutaro <nutarojj@ornl.gov> --- Makefile.target | 2 +- cpus.c | 13 ++++++- docs/simulation-sync.txt | 61 ++++++++++++++++++++++++++++++ include/qemu/thread.h | 11 ++++++ qemu-options.hx | 17 +++++++++ qqq.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++ qqq.h | 39 +++++++++++++++++++ util/qemu-thread-posix.c | 16 ++++++++ vl.c | 35 ++++++++++++++++- 9 files changed, 288 insertions(+), 4 deletions(-) create mode 100644 docs/simulation-sync.txt create mode 100644 qqq.c create mode 100644 qqq.h