d...@treblig.org writes:
> From: "Dr. David Alan Gilbert" <d...@treblig.org>
>
> migrate_zero_blocks is unused since
> eef0bae3a7 ("migration: Remove block migration")
>
> Remove it.
> That whole zero-blocks capability was just for old-school
> block migration anyway.
>
> Remove the capability as well.
>
> Signed-off-by: Dr. David Alan Gilbert <d...@treblig.org>
> ---
> migration/options.c | 8 --------
> migration/options.h | 1 -
> qapi/migration.json | 10 +---------
> 3 files changed, 1 insertion(+), 18 deletions(-)
>
> diff --git a/migration/options.c b/migration/options.c
> index 9460c5dee9..997e060612 100644
> --- a/migration/options.c
> +++ b/migration/options.c
> @@ -177,7 +177,6 @@ Property migration_properties[] = {
> DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
> DEFINE_PROP_MIG_CAP("x-rdma-pin-all", MIGRATION_CAPABILITY_RDMA_PIN_ALL),
> DEFINE_PROP_MIG_CAP("x-auto-converge",
> MIGRATION_CAPABILITY_AUTO_CONVERGE),
> - DEFINE_PROP_MIG_CAP("x-zero-blocks", MIGRATION_CAPABILITY_ZERO_BLOCKS),
> DEFINE_PROP_MIG_CAP("x-events", MIGRATION_CAPABILITY_EVENTS),
> DEFINE_PROP_MIG_CAP("x-postcopy-ram", MIGRATION_CAPABILITY_POSTCOPY_RAM),
> DEFINE_PROP_MIG_CAP("x-postcopy-preempt",
Property of (pseudo-)device "migration". The "x-" prefix suggests we
expect management software not to rely on it. Okay.
[...]
> diff --git a/qapi/migration.json b/qapi/migration.json
> index b66cccf107..82d0fc962e 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -389,13 +389,6 @@
> # footprint is mlock()'d on demand or all at once. Refer to
> # docs/rdma.txt for usage. Disabled by default. (since 2.0)
> #
> -# @zero-blocks: During storage migration encode blocks of zeroes
> -# efficiently. This essentially saves 1MB of zeroes per block on
> -# the wire. Enabling requires source and target VM to support
> -# this feature. To enable it is sufficient to enable the
> -# capability on the source VM. The feature is disabled by
> -# default. (since 1.6)
> -#
> # @events: generate events for each migration state change (since 2.4)
> #
> # @auto-converge: If enabled, QEMU will automatically throttle down
> @@ -483,7 +476,7 @@
> # Since: 1.2
> ##
> { 'enum': 'MigrationCapability',
> - 'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
> + 'data': ['xbzrle', 'rdma-pin-all', 'auto-converge',
> 'events', 'postcopy-ram',
> { 'name': 'x-colo', 'features': [ 'unstable' ] },
> 'release-ram',
This is used by migrate-set-capabilities and query-migrate-capabilities,
via ['MigrationCapabilityStatus'].
query-migrate-capabilities is unaffected: it couldn't return zero-blocks
anymore even before the patch.
migrate-set-capabilities changes incompatibly, I'm afraid. Before the
patch:
{"execute": "migrate-set-capabilities", "arguments": {"capabilities":
[{"capability": "zero-blocks", "state": true}]}}
{"return": {}}
Afterwards:
{"error": {"class": "GenericError", "desc": "Parameter 'capability' does
not accept value 'zero-blocks'"}}
If we had somehow rejected the capability when it made no sense,
removing it now it never makes sense would be obviously fine.
The straight & narrow path is to deprecate now, remove later.
If we believe nothing relies on it, we can bend the rules and remove
right away. Missing then: update to docs/about/removed-features.rst.
> @@ -542,7 +535,6 @@
> # {"state": false, "capability": "xbzrle"},
> # {"state": false, "capability": "rdma-pin-all"},
> # {"state": false, "capability": "auto-converge"},
> -# {"state": false, "capability": "zero-blocks"},
> # {"state": true, "capability": "events"},
> # {"state": false, "capability": "postcopy-ram"},
> # {"state": false, "capability": "x-colo"}
Example for query-migrate-capabilities. Good.
