On 08/11/2017 04:08 AM, Markus Armbruster wrote: > Eric Blake <ebl...@redhat.com> writes: > >> On 08/10/2017 01:30 PM, Markus Armbruster wrote: >>> A command is a query if it has no side effect and yields a result. >>> Such commands are typically named query-FOO, but there are exceptions. >>> >>> The basic idea is to find candidates with query-qmp-schema, filter out >>> the ones that aren't queries with an explicit blacklist, and test the >>> remaining ones against a QEMU with no special arguments. >>> >>> The current blacklist is just add-fd. >> >> I guess this is because it has no mandatory parameters. Hmm - I wonder >> if introspection should flag WHICH commands require an fd over SCM >> rights (I guess just add-fd) > > Actually, add-fd and getfd.
>
> An obvious alternative is of course adding another optional member to
> the command object, say a flag "takes file descriptors via SCM_RIGHTS".
> Do we need to express the number of file descriptors it takes? The
> underlying infrastructure supports several (TCP_MAX_FDS in
> char-socket.c), but the existing commands take just one.
Yeah, I was definitely leaning towards an additional annotation - maybe
where the .json file has:
{ 'command': 'add-fd', 'data': {'*fdset-id': 'int', '*opaque': 'str'},
'fds': 1, 'returns': 'AddfdInfo' }
where the new 'fds' is what designates that the command expects to
consume 1 fd by SCM_RIGHTS (defaults to 0 when not present, and could be
larger than one if a command is ever designed to take multiple fds in
one go - although I find SCM_RIGHTS tricky enough with 1 fd that passing
multiple is probably not necessary, so maybe false/true is better than
int). The introspection output would similarly expose the same optional
member for each command object, repeating what was present in the .json
file.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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