[Qemu-devel] [RFC] qemu-ga: Introduce guest-hibernate command

[Luiz Capitulino <lcapitulino@redhat.com>]

This is basically suspend to disk on a Linux guest.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---

This is an RFC because I did it as simple as possible and I'm open to
suggestions...

Now, while testing this or even "echo disk > /sys/power/state" I get several
funny results. Some times qemu just dies after printing that message:

 "Guest moved used index from 20151 to 1"

Some times it doesn't die, but I'm unable to log into the guest: I type
username & password but the terminal kind of locks (the shell doesn't run).

Some times it works...

 qapi-schema-guest.json     |   11 +++++++++++
 qga/guest-agent-commands.c |   19 +++++++++++++++++++
 2 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
index fde5971..2c5bbcf 100644
--- a/qapi-schema-guest.json
+++ b/qapi-schema-guest.json
@@ -215,3 +215,14 @@
 ##
 { 'command': 'guest-fsfreeze-thaw',
   'returns': 'int' }
+
+##
+# @guest-hibernate
+#
+# Save RAM contents to disk and powerdown the guest.
+#
+# Notes: This command doesn't return on success.
+#
+# Since: 1.1
+##
+{ 'command': 'guest-hibernate' }
diff --git a/qga/guest-agent-commands.c b/qga/guest-agent-commands.c
index 6da9904..9dd4060 100644
--- a/qga/guest-agent-commands.c
+++ b/qga/guest-agent-commands.c
@@ -550,6 +550,25 @@ int64_t qmp_guest_fsfreeze_thaw(Error **err)
 }
 #endif
 
+#define LINUX_SYS_STATE_FILE "/sys/power/state"
+
+void qmp_guest_hibernate(Error **err)
+{
+    int fd;
+
+    fd = open(LINUX_SYS_STATE_FILE, O_WRONLY);
+    if (fd < 0) {
+        error_set(err, QERR_OPEN_FILE_FAILED, LINUX_SYS_STATE_FILE);
+        return;
+    }
+
+    if (write(fd, "disk", 4) < 0) {
+        error_set(err, QERR_UNDEFINED_ERROR);
+    }
+
+    close(fd);
+}
+
 /* register init/cleanup routines for stateful command groups */
 void ga_command_state_init(GAState *s, GACommandState *cs)
 {
-- 
1.7.8.110.g4cb5d1.dirty