On 04/05/2016 21:44, Greg Kurz wrote:
> QEMU has currently two ways to prevent migration to occur:
> - migration blocker when it depends on runtime state
> - VMStateDescription.unmigratable when migration is not supported at all
>
> This patch gathers all the logic into a single function to be called from
> both the savevm and the migrate paths.
>
> This fixes a bug with 9p, at least, where savevm would succeed and the
> following would happen in the guest after loadvm:
>
> $ ls /host
> ls: cannot access /host: Protocol error
>
> With this patch:
>
> (qemu) savevm foo
> Migration is disabled when VirtFS export path '/' is mounted in the guest
> using mount_tag 'host'
>
> Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
> ---
>
> Since there has been some activity on 9p again since a few weeks, maybe it
> is not too late for 2.6, if everybody agrees the fix is ok ?
The patch is good, but I think the subject should be
savevm: fail if migration blockers are present
The subject you used would be good for the include/migration and
migration/migration.c parts alone (where you introduce the function
without any semantic change).
Apart from this,
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
Thanks,
Paolo
> include/migration/migration.h | 1 +
> migration/migration.c | 21 +++++++++++++++------
> migration/savevm.c | 2 +-
> 3 files changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/include/migration/migration.h b/include/migration/migration.h
> index ac2c12c2a518..9e36a97fc5e5 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -210,6 +210,7 @@ int migrate_fd_close(MigrationState *s);
> void add_migration_state_change_notifier(Notifier *notify);
> void remove_migration_state_change_notifier(Notifier *notify);
> MigrationState *migrate_init(const MigrationParams *params);
> +bool migration_is_blocked(Error **errp);
> bool migration_in_setup(MigrationState *);
> bool migration_has_finished(MigrationState *);
> bool migration_has_failed(MigrationState *);
> diff --git a/migration/migration.c b/migration/migration.c
> index 991313a8629a..afd883b78179 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -992,6 +992,20 @@ void qmp_migrate_incoming(const char *uri, Error **errp)
> once = false;
> }
>
> +bool migration_is_blocked(Error **errp)
> +{
> + if (qemu_savevm_state_blocked(errp)) {
> + return true;
> + }
> +
> + if (migration_blockers) {
> + *errp = error_copy(migration_blockers->data);
> + return true;
> + }
> +
> + return false;
> +}
> +
> void qmp_migrate(const char *uri, bool has_blk, bool blk,
> bool has_inc, bool inc, bool has_detach, bool detach,
> Error **errp)
> @@ -1014,12 +1028,7 @@ void qmp_migrate(const char *uri, bool has_blk, bool
> blk,
> return;
> }
>
> - if (qemu_savevm_state_blocked(errp)) {
> - return;
> - }
> -
> - if (migration_blockers) {
> - *errp = error_copy(migration_blockers->data);
> + if (migration_is_blocked(errp)) {
> return;
> }
>
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 16ba44379870..834664936dfc 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -1169,7 +1169,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
> MigrationState *ms = migrate_init(¶ms);
> ms->to_dst_file = f;
>
> - if (qemu_savevm_state_blocked(errp)) {
> + if (migration_is_blocked(errp)) {
> return -EINVAL;
> }
>
>
>
>
