qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH v2] qemu-ga: Add the guest-suspend command


From: Michael Roth
Subject: Re: [Qemu-devel] [PATCH v2] qemu-ga: Add the guest-suspend command
Date: Wed, 14 Dec 2011 09:50:04 -0600
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:8.0) Gecko/20111105 Thunderbird/8.0

On 12/14/2011 07:07 AM, Luiz Capitulino wrote:
On Tue, 13 Dec 2011 14:27:56 -0600
Michael Roth<address@hidden>  wrote:

On 12/13/2011 12:28 PM, Luiz Capitulino wrote:
It supports two modes: "hibernate" (which corresponds to S4) and
"sleep" (which corresponds to S3). It will try to execute the
pm-hibernate or pm-suspend scripts, if the scripts don't exist
the command will try to suspend by directly writing to the
"/sys/power/state" file.

An interesting implementation detail is how to cleanup the child's
status on termination, so that we don't create zombies. I've
choosen to ignore the SIGCHLD signal. This will cause the kernel to
automatically cleanup the child's status on its termination.

Signed-off-by: Luiz Capitulino<address@hidden>
---

I've tested this w/o any virtio driver, as they don't support S4 yet. For
S4 it seems to work ok. I couldn't fully test S3 because we lack a way to
resume from it, but by checking the logs it seems to work fine.

changelog
---------

v2

o Rename the command to 'guest-suspend'
o Add 'mode' parameter
o Use pm-utils scripts
o Cleanup child termination status

   qapi-schema-guest.json     |   17 +++++++++++
   qemu-ga.c                  |   11 +++++++-
   qga/guest-agent-commands.c |   64 
++++++++++++++++++++++++++++++++++++++++++++
   3 files changed, 91 insertions(+), 1 deletions(-)

diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
index 29989fe..656bde9 100644
--- a/qapi-schema-guest.json
+++ b/qapi-schema-guest.json
@@ -219,3 +219,20 @@
   ##
   { 'command': 'guest-fsfreeze-thaw',
     'returns': 'int' }
+
+##
+# @guest-suspend
+#
+# Suspend guest execution by entering ACPI power state S3 or S4.
+#
+# @mode: 'hibernate' RAM content is saved in the disk and the guest is
+#                    powered down (this corresponds to ACPI S4)
+#        'sleep'     execution is suspended but the RAM retains its contents
+#                    (this corresponds to ACPI S3)

'suspend' is generally associated with sleep, so maybe we should make
the mode optional and default to 'sleep'?

I'm not sure I like having defaults because we're choosing for the client.
If this were a human interface then it would make sense, but for a machine
one I don't think it does. Besides we don't seem to have a way to resume
from S3 so we're probably going to get reports about this command not working
(and that reminds me to add a note about that in the doc).

True, defaulting to broken behavior probably isn't a good idea :)



+#
+# Notes: This is an asynchronous request. There's no guarantee it will
+# succeed. Errors will be logged to guest's syslog.
+#
+# Since: 1.1
+##
+{ 'command': 'guest-suspend', 'data': { 'mode': 'str' } }
diff --git a/qemu-ga.c b/qemu-ga.c
index 60d4972..b32e96c 100644
--- a/qemu-ga.c
+++ b/qemu-ga.c
@@ -61,7 +61,7 @@ static void quit_handler(int sig)

   static void register_signal_handlers(void)
   {
-    struct sigaction sigact;
+    struct sigaction sigact, sigact_chld;
       int ret;

       memset(&sigact, 0, sizeof(struct sigaction));
@@ -76,6 +76,15 @@ static void register_signal_handlers(void)
       if (ret == -1) {
           g_error("error configuring signal handler: %s", strerror(errno));
       }
+
+    /* This should cause the kernel to automatically cleanup child
+       termination status */
+    memset(&sigact_chld, 0, sizeof(struct sigaction));
+    sigact_chld.sa_handler = SIG_IGN;
+    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..4799638 100644
--- a/qga/guest-agent-commands.c
+++ b/qga/guest-agent-commands.c
@@ -574,6 +574,70 @@ int64_t qmp_guest_fsfreeze_thaw(Error **err)
   }
   #endif

+#define LINUX_PM_UTILS_PATH "/usr/sbin"
+#define LINUX_SYS_STATE_FILE "/sys/power/state"
+
+void qmp_guest_suspend(const char *mode, Error **err)
+{
+    int ret, fd = -1;
+    const char *pmutils_bin;
+    char pmutils_bin_path[PATH_MAX];
+
+    if (strcmp(mode, "hibernate") == 0) {
+        pmutils_bin = "pm-hibernate";
+    } else if (strcmp(mode, "sleep") == 0) {
+        pmutils_bin = "pm-suspend";
+    } else {
+        error_set(err, QERR_INVALID_PARAMETER, "mode");
+        return;
+    }
+
+    snprintf(pmutils_bin_path, sizeof(pmutils_bin_path), "%s/%s",
+             LINUX_PM_UTILS_PATH, pmutils_bin);

I'd be surprised to find any distros where this isn't the case, but for
situations where the scripts aren't in /usr/sbin, maybe we'd be better
off just passing the command name to execlp() and letting it do the
search via PATH? The normal use case is that qemu-ga will get launched
as a service, so PATH should have the good stuff.

Ok, I'll make that change.


+
+    if (access(pmutils_bin_path, X_OK) != 0) {
+        pmutils_bin = NULL;
+        fd = open(LINUX_SYS_STATE_FILE, O_WRONLY);
+        if (fd<   0) {
+            error_set(err, QERR_OPEN_FILE_FAILED, LINUX_SYS_STATE_FILE);
+            return;
+        }
+    }
+
+    ret = fork();
+    if (ret == 0) {
+        /* child */
+        setsid();
+        fclose(stdin);
+        fclose(stdout);
+        fclose(stderr);
+
+        if (pmutils_bin) {
+            ret = execl(pmutils_bin_path, pmutils_bin, NULL);
+            if (ret) {
+                 slog("%s failed: %s", pmutils_bin_path, strerror(errno));
+             }
+        } else {
+            const char *cmd = strcmp(mode, "sleep") == 0 ? "mem" : "disk";
+            ret = write(fd, cmd, strlen(cmd));
+            if (ret<   0) {
+                slog("can't write to %s: %s\n", LINUX_SYS_STATE_FILE,
+                     strerror(errno));
+            }
+            close(fd);
+        }
+
+        exit(!!ret);
+    } else if (ret<   0) {
+        error_set(err, QERR_UNDEFINED_ERROR);
+        return;
+    }
+
+    if (!pmutils_bin) {
+        close(fd);
+    }
+}
+
   /* register init/cleanup routines for stateful command groups */
   void ga_command_state_init(GAState *s, GACommandState *cs)
   {






reply via email to

[Prev in Thread] Current Thread [Next in Thread]