[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] migration: add "return-path" capability
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH] migration: add "return-path" capability |
Date: |
Wed, 28 Jun 2017 10:25:34 +0100 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
* Peter Xu (address@hidden) wrote:
> When this capability is enabled, QEMU will use the return path even for
> precopy migration. This is helpful at least in one case when destination
> failed to load the image while source quited without confirmation. With
> return path, source will wait for the last response from destination,
> and if destination fails, it'll fail the migration on source, then the
> guest can be run again on the source (rather than assuming to be good,
> then the guest will be lost after source quits).
>
> It needs to be enabled explicitly on source, otherwise disabled.
>
> Signed-off-by: Peter Xu <address@hidden>
OK, so this looks fine, lets see what else we have.
The migration thread already calls savevm_send_open_return_path
if it's got a from_dst_file.
We already call 'await_return_path_close_on_source' in
migration_completion if we have a from_dst_file so that should
already work.
and on the incoming side, migration_incoming_state_destroy calls
migrate_send_rp_shut if it has a to_src_file. So that should close it
as well.
So that looks like a full set.
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> ---
> migration/migration.c | 16 +++++++++++++---
> migration/migration.h | 1 +
> qapi-schema.json | 5 ++++-
> 3 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index f588329..66fd81e 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1304,6 +1304,15 @@ bool migrate_use_block(void)
> return s->enabled_capabilities[MIGRATION_CAPABILITY_BLOCK];
> }
>
> +bool migrate_use_return_path(void)
> +{
> + MigrationState *s;
> +
> + s = migrate_get_current();
> +
> + return s->enabled_capabilities[MIGRATION_CAPABILITY_RETURN_PATH];
> +}
> +
> bool migrate_use_block_incremental(void)
> {
> MigrationState *s;
> @@ -1968,10 +1977,11 @@ void migrate_fd_connect(MigrationState *s)
> notifier_list_notify(&migration_state_notifiers, s);
>
> /*
> - * Open the return path; currently for postcopy but other things might
> - * also want it.
> + * Open the return path. For postcopy, it is used exclusively. For
> + * precopy, only if user specified "return-path" capability would
> + * QEMU uses the return path.
> */
> - if (migrate_postcopy_ram()) {
> + if (migrate_postcopy_ram() || migrate_use_return_path()) {
> if (open_return_path_on_source(s)) {
> error_report("Unable to open return-path for postcopy");
> migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
> diff --git a/migration/migration.h b/migration/migration.h
> index d9a268a..e41fb68 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -144,6 +144,7 @@ bool migrate_colo_enabled(void);
>
> bool migrate_use_block(void);
> bool migrate_use_block_incremental(void);
> +bool migrate_use_return_path(void);
>
> bool migrate_use_compression(void);
> int migrate_compress_level(void);
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 4b50b65..9e34cf7 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -900,12 +900,15 @@
> # offers more flexibility.
> # (Since 2.10)
> #
> +# @return-path: If enabled, migration will use the return path even
> +# for precopy. (since 2.10)
> +#
> # Since: 1.2
> ##
> { 'enum': 'MigrationCapability',
> 'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
> 'compress', 'events', 'postcopy-ram', 'x-colo', 'release-ram',
> - 'block' ] }
> + 'block', 'return-path' ] }
>
> ##
> # @MigrationCapabilityStatus:
> --
> 2.7.4
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK