* Markus Armbruster (arm...@redhat.com) wrote:
> This reverts commit 3df663e575f1876d7f3bc684f80e72fca0703d39.
> This reverts commit b605c47b57b58e61a901a50a0762dccf43d94783.
>
> Command line option --only-migratable is for disallowing any
> configuration that can block migration.
>
> Initially, --only-migratable set global variable @only_migratable.
>
> Commit 3df663e575 "migration: move only_migratable to MigrationState"
> replaced it by MigrationState member @only_migratable. That was a
> mistake.
>
> First, it doesn't make sense on the design level. MigrationState
> captures the state of an individual migration, but --only-migratable
> isn't a property of an individual migration, it's a restriction on
> QEMU configuration. With fault tolerance, we could have several
> migrations at once. --only-migratable would certainly protect all of
> them. Storing it in MigrationState feels inappropriate.
>
> Second, it contributes to a dependency cycle that manifests itself as
> a bug now.
>
> Putting @only_migratable into MigrationState means its available only
> after migration_object_init().
>
> We can't set it before migration_object_init(), so we delay setting it
> with a global property (this is fixup commit b605c47b57 "migration:
> fix handling for --only-migratable").
>
> We can't get it before migration_object_init(), so anything that uses
> it can only run afterwards.
>
> Since migrate_add_blocker() needs to obey --only-migratable, any code
> adding migration blockers can run only afterwards. This contributes
> to the following dependency cycle:
>
> * configure_blockdev() must run before machine_set_property()
> so machine properties can refer to block backends
>
> * machine_set_property() before configure_accelerator()
> so machine properties like kvm-irqchip get applied
>
> * configure_accelerator() before migration_object_init()
> so that Xen's accelerator compat properties get applied.
>
> * migration_object_init() before configure_blockdev()
> so configure_blockdev() can add migration blockers
>
> The cycle was closed when recent commit cda4aa9a5a0 "Create block
> backends before setting machine properties" added the first
> dependency, and satisfied it by violating the last one. Broke block
> backends that add migration blockers.
>
> Moving @only_migratable into MigrationState was a mistake. Revert it.
>
> This doesn't quite break the "migration_object_init() before
> configure_blockdev() dependency, since migrate_add_blocker() still has
> another dependency on migration_object_init(). To be addressed the
> next commit
>
> Conflicts:
> include/migration/misc.h
> migration/migration.c
> migration/migration.h
> vl.c
>
> Signed-off-by: Markus Armbruster <arm...@redhat.com>
> ---
> include/sysemu/sysemu.h | 1 +
> migration/migration.c | 5 ++---
> migration/migration.h | 3 ---
> migration/savevm.c | 2 +-
> vl.c | 9 ++-------
> 5 files changed, 6 insertions(+), 14 deletions(-)
>
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index 6065d9e420..5f133cae83 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -14,6 +14,7 @@
> /* vl.c */
>
> extern const char *bios_name;
> +extern int only_migratable;
> extern const char *qemu_name;
> extern QemuUUID qemu_uuid;
> extern bool qemu_uuid_set;
> diff --git a/migration/migration.c b/migration/migration.c
> index 69f75124c9..f6076e5295 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1707,7 +1707,7 @@ static GSList *migration_blockers;
>
> int migrate_add_blocker(Error *reason, Error **errp)
> {
> - if (migrate_get_current()->only_migratable) {
> + if (only_migratable) {
> error_propagate_prepend(errp, error_copy(reason),
> "disallowing migration blocker "
> "(--only_migratable) for: ");
> @@ -3337,7 +3337,7 @@ void migration_global_dump(Monitor *mon)
> monitor_printf(mon, "store-global-state: %s\n",
> ms->store_global_state ? "on" : "off");
> monitor_printf(mon, "only-migratable: %s\n",
> - ms->only_migratable ? "on" : "off");
> + only_migratable ? "on" : "off");
> monitor_printf(mon, "send-configuration: %s\n",
> ms->send_configuration ? "on" : "off");
> monitor_printf(mon, "send-section-footer: %s\n",
> @@ -3352,7 +3352,6 @@ void migration_global_dump(Monitor *mon)
> static Property migration_properties[] = {
> DEFINE_PROP_BOOL("store-global-state", MigrationState,
> store_global_state, true),
> - DEFINE_PROP_BOOL("only-migratable", MigrationState, only_migratable,
> false),
So I'm generally OK at this patch, but I'm worried whether this
is API?
Dave
> DEFINE_PROP_BOOL("send-configuration", MigrationState,
> send_configuration, true),
> DEFINE_PROP_BOOL("send-section-footer", MigrationState,
> diff --git a/migration/migration.h b/migration/migration.h
> index 0f986935e1..438f17edad 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -219,9 +219,6 @@ struct MigrationState
> */
> bool store_global_state;
>
> - /* Whether the VM is only allowing for migratable devices */
> - bool only_migratable;
> -
> /* Whether we send QEMU_VM_CONFIGURATION during migration */
> bool send_configuration;
> /* Whether we send section footer during migration */
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 1415001d1c..34bcad3807 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2844,7 +2844,7 @@ void vmstate_register_ram_global(MemoryRegion *mr)
> bool vmstate_check_only_migratable(const VMStateDescription *vmsd)
> {
> /* check needed if --only-migratable is specified */
> - if (!migrate_get_current()->only_migratable) {
> + if (!only_migratable) {
> return true;
> }
>
> diff --git a/vl.c b/vl.c
> index c1d5484e12..e4d7ad6b85 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -185,6 +185,7 @@ const char *prom_envs[MAX_PROM_ENVS];
> int boot_menu;
> bool boot_strict;
> uint8_t *boot_splash_filedata;
> +int only_migratable; /* turn it off unless user states otherwise */
> bool wakeup_suspend_enabled;
>
> int icount_align_option;
> @@ -3799,13 +3800,7 @@ int main(int argc, char **argv, char **envp)
> incoming = optarg;
> break;
> case QEMU_OPTION_only_migratable:
> - /*
> - * TODO: we can remove this option one day, and we
> - * should all use:
> - *
> - * "-global migration.only-migratable=true"
> - */
> - qemu_global_option("migration.only-migratable=true");
> + only_migratable = 1;
> break;
> case QEMU_OPTION_nodefaults:
> has_defaults = 0;
> --
> 2.17.2
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
