On Fri, Jan 07, 2011 at 03:13:25PM -0700, Alex Williamson wrote:
> The no_migrate save state flag is currently only checked in the
> last phase of migration. This means that we potentially waste
> a lot of time and bandwidth with the live state handlers before
> we ever check the no_migrate flags. The error message printed
> when we catch a non-migratable device doesn't get printed for
> a detached migration. And, no_migrate does nothing to prevent
> an incoming migration to a target that includes a non-migratable
> device. This attempts to fix all of these.
>
> One notable difference in behavior is that an outgoing migration
> now checks for non-migratable devices before ever connecting to
> the target system. This means the target will remain listening
> rather than exit from failure.
>
> Signed-off-by: Alex Williamson <alex.william...@redhat.com>
Minor nit:
The API of qemu_savevm_state_blocked is a bit strange.
functions should either return 0/1 values or 0 on success
negative on failure or a bool.
This API asks "is it blocked" and returns -EINVAL to
mean "yes". _blocked is also a bit ambigious:
it seems to imply a temporary condition.
How about we reverse the logic, call the new API
qemu_savevm_state_supported, qemu_savevm_state_enabled,
something like this?
Then you can return 0 if migration is possible,
-1 if not.
> ---
>
> v4:
> - fix braces noted by Jan
> - return error from qemu_savevm_state_blocked rather than fixed EINVAL
> at qemu_loadvm_state(), since it'a already using errno values
>
> v3:
>
> Daniel, adding you to see if libvirt cares about the difference in
> whether the target exits on migration failure as noted above.
>
> Also adding Michael as he's complained about the no_migrate check
> happening so late in the process.
>
> migration.c | 4 ++++
> savevm.c | 41 +++++++++++++++++++++++++++--------------
> sysemu.h | 1 +
> 3 files changed, 32 insertions(+), 14 deletions(-)
>
> diff --git a/migration.c b/migration.c
> index e5ba51c..d593b1d 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -88,6 +88,10 @@ int do_migrate(Monitor *mon, const QDict *qdict, QObject
> **ret_data)
> return -1;
> }
>
> + if (qemu_savevm_state_blocked(mon)) {
> + return -1;
> + }
> +
> if (strstart(uri, "tcp:", &p)) {
> s = tcp_start_outgoing_migration(mon, p, max_throttle, detach,
> blk, inc);
> diff --git a/savevm.c b/savevm.c
> index 90aa237..34c0d1a 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -1401,19 +1401,13 @@ static int vmstate_load(QEMUFile *f, SaveStateEntry
> *se, int version_id)
> return vmstate_load_state(f, se->vmsd, se->opaque, version_id);
> }
>
> -static int vmstate_save(QEMUFile *f, SaveStateEntry *se)
> +static void vmstate_save(QEMUFile *f, SaveStateEntry *se)
> {
> - if (se->no_migrate) {
> - return -1;
> - }
> -
> if (!se->vmsd) { /* Old style */
> se->save_state(f, se->opaque);
> - return 0;
> + return;
> }
> vmstate_save_state(f,se->vmsd, se->opaque);
> -
> - return 0;
> }
>
> #define QEMU_VM_FILE_MAGIC 0x5145564d
> @@ -1427,6 +1421,20 @@ static int vmstate_save(QEMUFile *f, SaveStateEntry
> *se)
> #define QEMU_VM_SECTION_FULL 0x04
> #define QEMU_VM_SUBSECTION 0x05
>
> +int qemu_savevm_state_blocked(Monitor *mon)
> +{
> + SaveStateEntry *se;
> +
> + QTAILQ_FOREACH(se, &savevm_handlers, entry) {
> + if (se->no_migrate) {
> + monitor_printf(mon, "state blocked by non-migratable device
> '%s'\n",
> + se->idstr);
> + return -EINVAL;
> + }
> + }
> + return 0;
> +}
> +
> int qemu_savevm_state_begin(Monitor *mon, QEMUFile *f, int blk_enable,
> int shared)
> {
> @@ -1508,7 +1516,6 @@ int qemu_savevm_state_iterate(Monitor *mon, QEMUFile *f)
> int qemu_savevm_state_complete(Monitor *mon, QEMUFile *f)
> {
> SaveStateEntry *se;
> - int r;
>
> cpu_synchronize_all_states();
>
> @@ -1541,11 +1548,7 @@ int qemu_savevm_state_complete(Monitor *mon, QEMUFile
> *f)
> qemu_put_be32(f, se->instance_id);
> qemu_put_be32(f, se->version_id);
>
> - r = vmstate_save(f, se);
> - if (r < 0) {
> - monitor_printf(mon, "cannot migrate with device '%s'\n",
> se->idstr);
> - return r;
> - }
> + vmstate_save(f, se);
> }
>
> qemu_put_byte(f, QEMU_VM_EOF);
> @@ -1575,6 +1578,11 @@ static int qemu_savevm_state(Monitor *mon, QEMUFile *f)
> saved_vm_running = vm_running;
> vm_stop(0);
>
> + ret = qemu_savevm_state_blocked(mon);
> + if (ret < 0) {
> + goto out;
> + }
> +
> ret = qemu_savevm_state_begin(mon, f, 0, 0);
> if (ret < 0)
> goto out;
> @@ -1692,6 +1700,11 @@ int qemu_loadvm_state(QEMUFile *f)
> unsigned int v;
> int ret;
>
> + ret = qemu_savevm_state_blocked(default_mon);
> + if (ret < 0) {
> + return ret;
> + }
> +
> v = qemu_get_be32(f);
> if (v != QEMU_VM_FILE_MAGIC)
> return -EINVAL;
> diff --git a/sysemu.h b/sysemu.h
> index e728ea1..eefaba5 100644
> --- a/sysemu.h
> +++ b/sysemu.h
> @@ -75,6 +75,7 @@ void qemu_announce_self(void);
>
> void main_loop_wait(int nonblocking);
>
> +int qemu_savevm_state_blocked(Monitor *mon);
> int qemu_savevm_state_begin(Monitor *mon, QEMUFile *f, int blk_enable,
> int shared);
> int qemu_savevm_state_iterate(Monitor *mon, QEMUFile *f);
