[Qemu-devel] [PATCH 2/2] qemu-ga: Add the guest-suspend command

[Luiz Capitulino <lcapitulino@redhat.com>]

For now it only supports the "hibernate" mode, which suspends the
guest to disk.

This command will try to execute the scripts provided by the pm-utils
package. If that fails, it will try to suspend manually by writing
to the "/sys/power/state" file.

To reap terminated children, a new signal handler is installed to
catch SIGCHLD signals and a non-blocking call to waitpid() is done to
collect their exit statuses.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 qapi-schema-guest.json     |   23 ++++++++++++++++++
 qemu-ga.c                  |   17 ++++++++++++-
 qga/guest-agent-commands.c |   55 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 94 insertions(+), 1 deletions(-)

diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
index 5f8a18d..b151670 100644
--- a/qapi-schema-guest.json
+++ b/qapi-schema-guest.json
@@ -219,3 +219,26 @@
 ##
 { 'command': 'guest-fsfreeze-thaw',
   'returns': 'int' }
+
+##
+# @guest-suspend
+#
+# Suspend guest execution by changing the guest's ACPI power state.
+#
+# This command tries to execute the scripts provided by the pm-utils
+# package. If they are not available, it will perform the suspend
+# operation by manually writing to a sysfs file.
+#
+# For the best results it's strongly recommended to have the pm-utils
+# package installed in the guest.
+#
+# @mode: 'hibernate' RAM content is saved to the disk and the guest is
+#                    powered off (this corresponds to ACPI S4)
+#
+# Notes: This is an asynchronous request. There's no guarantee a response
+# will be sent. Errors will be logged to guest's syslog. More modes are
+# expected in the future.
+#
+# Since: 1.1
+##
+{ 'command': 'guest-suspend', 'data': { 'mode': 'str' } }
diff --git a/qemu-ga.c b/qemu-ga.c
index 98e4dfe..5b7a7a5 100644
--- a/qemu-ga.c
+++ b/qemu-ga.c
@@ -17,6 +17,7 @@
 #include <getopt.h>
 #include <termios.h>
 #include <syslog.h>
+#include <sys/wait.h>
 #include "qemu_socket.h"
 #include "json-streamer.h"
 #include "json-parser.h"
@@ -59,9 +60,15 @@ static void quit_handler(int sig)
     }
 }
 
+static void child_handler(int sig)
+{
+    int status;
+    waitpid(-1, &status, WNOHANG);
+}
+
 static void register_signal_handlers(void)
 {
-    struct sigaction sigact;
+    struct sigaction sigact, sigact_chld;
     int ret;
 
     memset(&sigact, 0, sizeof(struct sigaction));
@@ -76,6 +83,14 @@ static void register_signal_handlers(void)
     if (ret == -1) {
         g_error("error configuring signal handler: %s", strerror(errno));
     }
+
+    memset(&sigact_chld, 0, sizeof(struct sigaction));
+    sigact_chld.sa_handler = child_handler;
+    sigact_chld.sa_flags = SA_NOCLDSTOP;
+    ret = sigaction(SIGCHLD, &sigact_chld, NULL);
+    if (ret == -1) {
+        g_error("error configuring signal handler: %s", strerror(errno));
+    }
 }
 
 static void usage(const char *cmd)
diff --git a/qga/guest-agent-commands.c b/qga/guest-agent-commands.c
index a09c8ca..19f29c6 100644
--- a/qga/guest-agent-commands.c
+++ b/qga/guest-agent-commands.c
@@ -574,6 +574,61 @@ int64_t qmp_guest_fsfreeze_thaw(Error **err)
 }
 #endif
 
+#define LINUX_SYS_STATE_FILE "/sys/power/state"
+
+void qmp_guest_suspend(const char *mode, Error **err)
+{
+    pid_t pid;
+    const char *pmutils_bin;
+
+    /* TODO implement 'sleep' and 'hybrid' modes once qemu is fixed to
+       support them */
+    if (strcmp(mode, "hibernate") == 0) {
+        pmutils_bin = "pm-hibernate";
+    } else {
+        error_set(err, QERR_INVALID_PARAMETER, "mode");
+        return;
+    }
+
+    pid = fork();
+    if (pid == 0) {
+        /* child */
+        int fd;
+
+        setsid();
+        fclose(stdin);
+        fclose(stdout);
+        fclose(stderr);
+
+        execlp(pmutils_bin, pmutils_bin, NULL);
+
+        /* 
+         * The exec call should not return, if it does something went wrong.
+         * In this case we try to suspend manually if 'mode' is 'hibernate'
+         */
+        slog("could not execute %s: %s\n", pmutils_bin, strerror(errno));
+        slog("trying to suspend using the manual method...\n");
+
+        fd = open(LINUX_SYS_STATE_FILE, O_WRONLY);
+        if (fd < 0) {
+            slog("can't open file %s: %s\n", LINUX_SYS_STATE_FILE,
+                    strerror(errno));
+            exit(1);
+        }
+
+        if (write(fd, "disk", 4) < 0) {
+            slog("can't write to %s: %s\n", LINUX_SYS_STATE_FILE,
+                    strerror(errno));
+            exit(1);
+        }
+
+        exit(0);
+    } else if (pid < 0) {
+        error_set(err, QERR_UNDEFINED_ERROR);
+        return;
+    }
+}
+
 /* register init/cleanup routines for stateful command groups */
 void ga_command_state_init(GAState *s, GACommandState *cs)
 {
-- 
1.7.8.2.321.g4570a.dirty