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migration: Avoid false-positive on non-supported scenarios for zero-copy-send

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Migration with zero-copy-send currently has it's limitations, as it can't
be used with TLS nor any kind of compression. In such scenarios, it should
output errors during parameter / capability setting.

But currently there are some ways of setting this not-supported scenarios
without printing the error message:

!) For 'compression' capability, it works by enabling it together with
zero-copy-send. This happens because the validity test for zero-copy uses
the helper unction migrate_use_compression(), which check for compression
presence in s->enabled_capabilities[MIGRATION_CAPABILITY_COMPRESS].

The point here is: the validity test happens before the capability gets
enabled. If all of them get enabled together, this test will not return
error.

In order to fix that, replace migrate_use_compression() by directly testing
the cap_list parameter migrate_caps_check().

2) For features enabled by parameters such as TLS & 'multifd_compression',
there was also a possibility of setting non-supported scenarios: setting
zero-copy-send first, then setting the unsupported parameter.

In order to fix that, also add a check for parameters conflicting with
zero-copy-send on migrate_params_check().

3) XBZRLE is also a compression capability, so it makes sense to also add
it to the list of capabilities which are not supported with zero-copy-send.

Fixes: 1abaec9a1b2c ("migration: Change zero_copy_send from migration parameter to migration capability")
Signed-off-by: Leonardo Bras <leobras@redhat.com>
Message-Id: <20220719122345.253713-1-leobras@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Leonardo Bras 2022-07-19 09:23:45 -03:00 committed by Dr. David Alan Gilbert
parent 4a8f19c95c
commit 90eb69e4f1
1 changed files with 14 additions and 1 deletions
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15
migration/migration.c
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@ -1306,7 +1306,9 @@ static bool migrate_caps_check(bool *cap_list,
#ifdef CONFIG_LINUX
if (cap_list[MIGRATION_CAPABILITY_ZERO_COPY_SEND] &&
(!cap_list[MIGRATION_CAPABILITY_MULTIFD] ||
migrate_use_compression() ||
cap_list[MIGRATION_CAPABILITY_COMPRESS] ||
cap_list[MIGRATION_CAPABILITY_XBZRLE] ||
migrate_multifd_compression() ||
migrate_use_tls())) {
error_setg(errp,
"Zero copy only available for non-compressed non-TLS multifd migration");
@ -1550,6 +1552,17 @@ static bool migrate_params_check(MigrationParameters *params, Error **errp)
error_prepend(errp, "Invalid mapping given for block-bitmap-mapping: ");
return false;
}
#ifdef CONFIG_LINUX
if (migrate_use_zero_copy_send() &&
((params->has_multifd_compression && params->multifd_compression) ||
(params->has_tls_creds && params->tls_creds && *params->tls_creds))) {
error_setg(errp,
"Zero copy only available for non-compressed non-TLS multifd migration");
return false;
}
#endif
return true;
}