"Michael S. Tsirkin" <[email protected]> writes: > On Mon, Oct 06, 2025 at 03:23:06PM +0200, Markus Armbruster wrote: >> Vladimir Sementsov-Ogievskiy <[email protected]> writes: >> >> > To migrate virtio-net TAP device backend (including open fds) locally, >> > user should simply set migration parameter >> > >> > backend-transfer = ["virtio-net-tap"] >> > >> > Why not simple boolean? To simplify migration to further versions, >> > when more devices will support backend-transfer migration. >> > >> > Alternatively, we may add per-device option to disable backend-transfer >> > migration, but still: >> > >> > 1. It's more comfortable to set same capabilities/parameters on both >> > source and target QEMU, than care about each device. >> > >> > 2. To not break the design, that machine-type + device options + >> > migration capabilities and parameters are fully define the resulting >> > migration stream. We'll break this if add in future more >> > backend-transfer support in devices under same backend-transfer=true >> > parameter. >> > >> > Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]> >> > --- >> > include/qapi/util.h | 17 ++++++++++++++++ >> > migration/options.c | 32 ++++++++++++++++++++++++++++++ >> > migration/options.h | 2 ++ >> > qapi/migration.json | 47 ++++++++++++++++++++++++++++++++++++--------- >> > 4 files changed, 89 insertions(+), 9 deletions(-) >> > >> > diff --git a/include/qapi/util.h b/include/qapi/util.h >> > index 29bc4eb865..b953402416 100644 >> > --- a/include/qapi/util.h >> > +++ b/include/qapi/util.h >> > @@ -69,4 +69,21 @@ int parse_qapi_name(const char *name, bool complete); >> > _len; \ >> > }) >> > >> > +/* >> > + * For any GenericList @list, return true if it contains specified >> > + * element. >> > + */ >> > +#define QAPI_LIST_CONTAINS(list, el) \ >> > + ({ \ >> > + bool _found = false; \ >> > + typeof_strip_qual(list) _tail; \ >> > + for (_tail = list; _tail != NULL; _tail = _tail->next) { \ >> > + if (_tail->value == el) { \ >> > + _found = true; \ >> > + break; \ >> > + } \ >> > + } \ >> > + _found; \ >> > + }) >> > + >> >> Not a fan of lengthy macros. >> >> There's a single use below: migrate_virtio_net_tap(). I can't see >> potential uses for such a search in existing code. > > However, QAPI_LIST_FOR_EACH can potentially be used to implement > QAPI_LIST_LENGTH. > > #define QAPI_LIST_FOR_EACH(list, tail) \ > for (tail = list; tail != NULL; tail = tail->next) > > and > > #define QAPI_LIST_LENGTH(list) \ > ({ \ > size_t _len = 0; \ > typeof_strip_qual(list) _tail; \ > QAPI_LIST_FOR_EACH(list, tail) { \ > _len++; \ > } \ > _len; \ > })
Yes, but would QAPI_LIST_FOR_EACH be better than the straightfoward & simple for-loop? [...]
