From patchwork Wed Sep 7 17:53:18 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "James J. Nutaro" X-Patchwork-Id: 667114 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3sTrgy2fMcz9s3s for ; Thu, 8 Sep 2016 03:54:22 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; secure) header.d=ornl.gov header.i=@ornl.gov header.b=BAhfmFMT; dkim-atps=neutral Received: from localhost ([::1]:42286 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bhh3D-00006H-Gn for incoming@patchwork.ozlabs.org; Wed, 07 Sep 2016 13:54:19 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54541) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bhh2X-00081e-US for qemu-devel@nongnu.org; Wed, 07 Sep 2016 13:53:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bhh2S-0001gd-Oy for qemu-devel@nongnu.org; Wed, 07 Sep 2016 13:53:36 -0400 Received: from mta02.ornl.gov ([128.219.177.136]:23147) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bhh2S-0001gB-FS for qemu-devel@nongnu.org; Wed, 07 Sep 2016 13:53:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ornl.gov; i=@ornl.gov; q=dns/txt; s=p20151116; t=1473270812; x=1504806812; h=from:to:cc:subject:date:message-id; bh=Kzaus2PNcYzq+mzgy0+JITUFm+EFLLOeXfZPD0zofaY=; b=BAhfmFMT/G040yRMAV05Dr5hFceMYcJybRhzEELVsZQXv7J1WAylgGOF 9SQsNdEDytd6LITgcAGGQZmOh8JPgI+OTlqlqCBhkXusYqbecvHmXGvea XISqKWTg8GjnDvJk6j49ziwwawar6rt68RCjRKNpCLB7B74xh2Uq6GA1B gdPetafT78Ukn6SAAZNSPkRgdDsLrON5fT31tQxXM4cpWCs8kjYJO1GPc TNdWK0MIJKfhC66Y366rgZ/vKLY+8JWsyFxAQbI5FY4ENFxS3U9CaG1r4 rZi0Z52wD9tyH8F21ynoPZqaVaIYo0GOvlUK+T7Vbuvc7SSO1OBslpT1X Q==; X-SG: RELAYLIST X-IronPort-AV: E=Sophos;i="5.30,296,1470715200"; d="scan'208";a="111683828" Received: from emgwy1.ornl.gov ([160.91.254.9]) by iron2.ornl.gov with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Sep 2016 13:53:29 -0400 Received: from stygia.ornl.gov (stygia.ornl.gov [160.91.240.222]) by emgwy1.ornl.gov (Postfix) with ESMTP id 3sTrfx1Rrpz7tGq; Wed, 7 Sep 2016 13:53:29 -0400 (EDT) From: "James J. Nutaro" To: qemu-devel@nongnu.org Date: Wed, 7 Sep 2016 13:53:18 -0400 Message-Id: <1473270798-12193-1-git-send-email-nutarojj@ornl.gov> X-Mailer: git-send-email 2.5.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 128.219.177.136 Subject: [Qemu-devel] [PATCH v3] qqq: module for synchronizing with a simulation X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "James J. Nutaro" Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" This patch adds an interface for pacing the execution of QEMU to match its rtc with an external simulation clock. Its aim is to permit QEMU to be used as a module within a larger simulation system. This revision (v3) corrects formatting errors detected by Patchew. Signed-off-by: James J. Nutaro --- Makefile.target | 3 ++ docs/simulation-sync.txt | 60 ++++++++++++++++++++++++++ qemu-options.hx | 16 +++++++ qqq.c | 109 +++++++++++++++++++++++++++++++++++++++++++++++ qqq.h | 35 +++++++++++++++ vl.c | 32 ++++++++++++++ 6 files changed, 255 insertions(+) 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 8c7a072..b7f6c4c 100644 --- a/Makefile.target +++ b/Makefile.target @@ -103,6 +103,9 @@ obj-$(CONFIG_LIBDECNUMBER) += libdecnumber/dpd/decimal32.o obj-$(CONFIG_LIBDECNUMBER) += libdecnumber/dpd/decimal64.o obj-$(CONFIG_LIBDECNUMBER) += libdecnumber/dpd/decimal128.o +# qqq +obj-y += qqq.o + ######################################################### # Linux user emulator target diff --git a/docs/simulation-sync.txt b/docs/simulation-sync.txt new file mode 100644 index 0000000..2133093 --- /dev/null +++ b/docs/simulation-sync.txt @@ -0,0 +1,60 @@ += 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/qemu-options.hx b/qemu-options.hx index a71aaf8..d52cc9c 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -3359,6 +3359,22 @@ 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. 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=on|off,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..f94711f --- /dev/null +++ b/qqq.c @@ -0,0 +1,109 @@ + +#include "qemu/osdep.h" +#include "qemu/timer.h" +#include "qemu/main-loop.h" +#include "sysemu/cpus.h" +#include "qqq.h" +#include + +/* This is a Linux only feature */ + +#ifndef _WIN32 + +#include +#include + +static int elapsed; +static int time_advance = -1; +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) +{ + /* If we got the time advance in fd_read, then don't do it + * again here. */ + if (time_advance < 0) { + /* Otherwise read the value from the pipe */ + time_advance = read_mem_value(); + } + /* Schedule the next synchronization point */ + timer_mod(sync_timer, t + time_advance); + /* Note that we need to read the time advance again on the next pass */ + time_advance = -1; +} + +static void sync_func(void *data) +{ + /* Report the actual elapsed time. */ + int64_t tnow = qemu_clock_get_us(QEMU_CLOCK_VIRTUAL); + elapsed = tnow - t; + write_mem_value(elapsed); + /* Update our time of last event */ + t = tnow; + /* Schedule the next event */ + schedule_next_event(); +} + +static void fd_read(void *opaque) +{ + /* Read the time advance if its becomes available + * before our timer expires */ + time_advance = read_mem_value(); +} + +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(); + /* Register the file descriptor with qemu. This should ensure + * the emulator doesn't pause for lack of I/O and thereby + * cause the attached simulator to pause with it. */ + qemu_set_fd_handler(read_fd, fd_read, NULL, NULL); +} + +#else + +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..40a24e3 --- /dev/null +++ b/qqq.h @@ -0,0 +1,35 @@ +/* + * 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); + +#endif diff --git a/vl.c b/vl.c index ee557a1..fe72990 100644 --- a/vl.c +++ b/vl.c @@ -122,6 +122,8 @@ 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 @@ -231,6 +233,23 @@ static struct { { .driver = "virtio-vga", .flag = &default_vga }, }; +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_rtc_opts = { .name = "rtc", .head = QTAILQ_HEAD_INITIALIZER(qemu_rtc_opts.head), @@ -2952,6 +2971,7 @@ int main(int argc, char **argv, char **envp) DisplayState *ds; int cyls, heads, secs, translation; QemuOpts *hda_opts = NULL, *opts, *machine_opts, *icount_opts = NULL; + QemuOpts *qqq_opts = NULL; QemuOptsList *olist; int optind; const char *optarg; @@ -2987,6 +3007,7 @@ int main(int argc, char **argv, char **envp) module_call_init(MODULE_INIT_QOM); + qemu_add_opts(&qemu_qqq_opts); qemu_add_opts(&qemu_drive_opts); qemu_add_drive_opts(&qemu_legacy_drive_opts); qemu_add_drive_opts(&qemu_common_drive_opts); @@ -3847,6 +3868,13 @@ 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); @@ -4350,6 +4378,10 @@ int main(int argc, char **argv, char **envp) /* spice needs the timers to be initialized by this point */ qemu_spice_init(); + if (qqq_opts) { + setup_qqq(qqq_opts); + } + cpu_ticks_init(); if (icount_opts) { if (kvm_enabled() || xen_enabled()) {