On Thu, Jul 31, 2008 at 04:50:51PM +0200, Chris Lalancette wrote:
> We've been trying to plumb libvirt to do KVM migration. One of the stumbling
> blocks we are running into, however, is that libvirt expects to be able to use
> the Qemu monitor both before and after migration has taken place, on both the
> source and destination nodes. After migration has taken place is no problem;
> we
> return to the main qemu select() loop, and we can run monitor commands.
> However, before migration, on the destination side, when we start qemu with a
> command-line like:
>
> qemu-kvm -M pc -S blah blah -incoming tcp://0:4444
>
> we can't run any monitor commands since the migration code is synchronously
> waiting for an incoming tcp connection. To get around this, the following
> patch
> adds a new monitor command called "migrate_incoming"; it takes all of the same
> parameters as the command-line option, but just starts it later. To make sure
> it is safe, you actually have to start with "-incoming monitor"; if you run it
> without that, it will just spit an error at you. So with this in place,
> libvirt
> can do the equivalent of:
>
> qemu-kvm -M pc -S blah blah -incoming monitor
> (qemu) info cpus
> ...other commands
> (qemu) migrate_incoming tcp://0:4444
> ...wait for migration to start, and then complete
> (qemu) info block
> ...etc.
>
> Signed-off-by: Chris Lalancette <[EMAIL PROTECTED]>
> diff --git a/qemu/monitor.c b/qemu/monitor.c
> index 20dcca6..c11b82c 100644
> --- a/qemu/monitor.c
> +++ b/qemu/monitor.c
> @@ -504,6 +504,25 @@ static void do_cont(void)
> vm_start();
> }
>
> +static void do_migrate_incoming(const char *incom)
> +{
> + extern int incoming_monitor;
> +
> + if (!incoming_monitor) {
> + term_printf("FAIL: Can only use the migrate-incoming command with
> -incoming monitor\n");
> + }
> + else {
> + int rc;
> +
> + rc = migrate_incoming(incom);
You probably want to set 'incoming_monitor = 0' here, to protect against
someone accidentially running it multiple times.
> + if (rc != 0) {
> + fprintf(stderr, "Migration failed rc=%d\n", rc);
> + exit(rc);
> + }
And some whitespace issues here..
> + vm_start();
> + }
> +}
> +
> #ifdef CONFIG_GDBSTUB
> static void do_gdbserver(const char *port)
> {
> @@ -1486,6 +1505,7 @@ static term_cmd_t term_cmds[] = {
> "", "cancel the current VM migration" },
> { "migrate_set_speed", "s", do_migrate_set_speed,
> "value", "set maximum speed (in bytes) for migrations" },
> + { "migrate_incoming", "s", do_migrate_incoming, "incom", "incoming
> string" },
> { "cpu_set", "is", do_cpu_set_nr, "cpu [online|offline]", "change cpu
> state" },
> #if defined(TARGET_I386) || defined(TARGET_X86_64)
> { "drive_add", "iss", drive_hot_add, "pcibus pcidevfn
> [file=file][,if=type][,bus=n]\n"
> diff --git a/qemu/vl.c b/qemu/vl.c
> index e1762ee..9b5f113 100644
> --- a/qemu/vl.c
> +++ b/qemu/vl.c
> @@ -229,6 +229,7 @@ int cursor_hide = 1;
> int graphic_rotate = 0;
> int daemonize = 0;
> const char *incoming;
> +int incoming_monitor = 0;
> const char *option_rom[MAX_OPTION_ROMS];
> int nb_option_roms;
> int semihosting_enabled = 0;
> @@ -9673,11 +9675,16 @@ int main(int argc, char **argv)
> if (incoming) {
> int rc;
>
> - rc = migrate_incoming(incoming);
> - if (rc != 0) {
> - fprintf(stderr, "Migration failed rc=%d\n", rc);
> - exit(rc);
> - }
> + if (strncmp(incoming, "monitor", 7) == 0) {
> + incoming_monitor = 1;
> + }
> + else {
> + rc = migrate_incoming(incoming);
> + if (rc != 0) {
> + fprintf(stderr, "Migration failed rc=%d\n", rc);
> + exit(rc);
> + }
> + }
Rather than putting the strncmp("monitor") into vl.c, I'd just leave
this part as is. Put the logic into the 'migrate_incoming()' method
so that it just sets the 'incoming_monitor' flag and then returns
immediately. That would allwo the 'incoming_Monitor' flag to be declared
static to the migrate.c file, instead of polluting vl.c
Daniel
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