Re: [RFC PATCH v3 07/30] migration: Add fixed-ram URI compatibility check

[Fabiano Rosas <farosas@suse.de>]

Peter Xu <peterx@redhat.com> writes:

> On Mon, Nov 27, 2023 at 05:25:49PM -0300, Fabiano Rosas wrote:
>> The fixed-ram migration format needs a channel that supports seeking
>> to be able to write each page to an arbitrary offset in the migration
>> stream.
>> 
>> Signed-off-by: Fabiano Rosas <farosas@suse.de>
>> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
>> ---
>> - avoided overwriting errp in compatibility check
>> ---
>>  migration/migration.c | 16 ++++++++++++++++
>>  1 file changed, 16 insertions(+)
>> 
>> diff --git a/migration/migration.c b/migration/migration.c
>> index 28a34c9068..897ed1db67 100644
>> --- a/migration/migration.c
>> +++ b/migration/migration.c
>> @@ -135,10 +135,26 @@ static bool transport_supports_multi_channels(SocketAddress *saddr)
>>             saddr->type == SOCKET_ADDRESS_TYPE_VSOCK;
>>  }
>>  
>> +static bool migration_needs_seekable_channel(void)
>> +{
>> +    return migrate_fixed_ram();
>> +}
>> +
>> +static bool transport_supports_seeking(MigrationAddress *addr)
>> +{
>> +    return addr->transport == MIGRATION_ADDRESS_TYPE_FILE;
>> +}
>
> What about TYPE_FD?  Is it going to be supported later?
>

Sorry, I missed this one.

Yes, and thanks for asking because I just remembered I have code for
this lost in a git stash somewhere. I'll include it in v4.

>> +
>>  static bool
>>  migration_channels_and_transport_compatible(MigrationAddress *addr,
>>                                              Error **errp)
>>  {
>> +    if (migration_needs_seekable_channel() &&
>> +        !transport_supports_seeking(addr)) {
>> +        error_setg(errp, "Migration requires seekable transport (e.g. file)");
>> +        return false;
>> +    }
>> +
>>      if (migration_needs_multiple_sockets() &&
>>          (addr->transport == MIGRATION_ADDRESS_TYPE_SOCKET) &&
>>          !transport_supports_multi_channels(&addr->u.socket)) {
>> -- 
>> 2.35.3
>>