From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58396) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aRh7c-0005p9-Su for qemu-devel@nongnu.org; Fri, 05 Feb 2016 09:12:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aRh7W-0006yP-Cu for qemu-devel@nongnu.org; Fri, 05 Feb 2016 09:12:28 -0500 Received: from mta01.ornl.gov ([128.219.177.14]:44823) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aRh7W-0006xl-3i for qemu-devel@nongnu.org; Fri, 05 Feb 2016 09:12:22 -0500 From: "James J. Nutaro" Date: Fri, 5 Feb 2016 09:12:16 -0500 Message-Id: <1454681536-5487-1-git-send-email-nutarojj@ornl.gov> Subject: [Qemu-devel] [PATCH] qqq: module for synchronizing with a simulation clock List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, eblake@redhat.com Cc: "James J. Nutaro" 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 --- 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 diff --git a/Makefile.target b/Makefile.target index 34ddb7e..a158877 100644 --- a/Makefile.target +++ b/Makefile.target @@ -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 diff --git a/cpus.c b/cpus.c index 882b618..09ec596 100644 --- a/cpus.c +++ b/cpus.c @@ -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) { diff --git a/docs/simulation-sync.txt b/docs/simulation-sync.txt new file mode 100644 index 0000000..0f053b3 --- /dev/null +++ b/docs/simulation-sync.txt @@ -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/ + diff --git a/include/qemu/thread.h b/include/qemu/thread.h index 5114ec8..5b4beb9 100644 --- a/include/qemu/thread.h +++ b/include/qemu/thread.h @@ -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); diff --git a/qemu-options.hx b/qemu-options.hx index f31a240..2d4f06e 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -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=]\n" \ " enable virtual instruction counter with 2^N clock ticks per\n" \ diff --git a/qqq.c b/qqq.c new file mode 100644 index 0000000..bc41e70 --- /dev/null +++ b/qqq.c @@ -0,0 +1,98 @@ + +#include "qemu/osdep.h" +#include "qemu/timer.h" +#include "qqq.h" + +/* This is a Linux only feature */ + +#ifndef _WIN32 + +#include +#include + +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 diff --git a/qqq.h b/qqq.h new file mode 100644 index 0000000..50e67bc --- /dev/null +++ b/qqq.h @@ -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 + * + */ +#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 diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c index dbd8094..8d95395 100644 --- a/util/qemu-thread-posix.c +++ b/util/qemu-thread-posix.c @@ -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; diff --git a/vl.c b/vl.c index f043009..8c36636 100644 --- a/vl.c +++ b/vl.c @@ -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) { -- 2.5.0