Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru> writes: > On 18.10.23 09:47, Markus Armbruster wrote: >> Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru> writes: >> >>> On 17.10.23 18:00, Markus Armbruster wrote: >>>> Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru> writes: >>>> >>>>> Send a new event when guest reads virtio-pci config after >>>>> virtio_notify_config() call. >>>>> >>>>> That's useful to check that guest fetched modified config, for example >>>>> after resizing disk backend. >>>>> >>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru> >> [...] >> >>>>> diff --git a/qapi/qdev.json b/qapi/qdev.json >>>>> index 2468f8bddf..37a8785b81 100644 >>>>> --- a/qapi/qdev.json >>>>> +++ b/qapi/qdev.json >>>>> @@ -329,3 +329,25 @@ >>>>> # Since: 8.2 >>>>> ## >>>>> { 'command': 'x-device-sync-config', 'data': {'id': 'str'} } >>>>> + >>>>> +## >>>>> +# @X_CONFIG_READ: >>>>> +# >>>>> +# Emitted whenever guest reads virtio device config after config change. >>>>> +# >>>>> +# @device: device name >>>>> +# >>>>> +# @path: device path >>>>> +# >>>>> +# Since: 5.0.1-24 >>>>> +# >>>>> +# Example: >>>>> +# >>>>> +# <- { "event": "X_CONFIG_READ", >>>>> +# "data": { "device": "virtio-net-pci-0", >>>>> +# "path": "/machine/peripheral/virtio-net-pci-0" }, >>>>> +# "timestamp": { "seconds": 1265044230, "microseconds": 450486 } } >>>>> +# >>>>> +## >>>>> +{ 'event': 'X_CONFIG_READ', >>>>> + 'data': { '*device': 'str', 'path': 'str' } } >>>> >>>> The commit message talks about event CONFIG_READ, but you actually name >>>> it x-device-sync-config. >>> >>> will fix >>> >>>> I figure you use x- to signify "unstable". Please use feature flag >>>> 'unstable' for that. See docs/devel/qapi-code-gen.rst section >>>> "Features", in particular "Special features", and also the note on x- in >>>> section "Naming rules and reserved names". >>> >>> OK, will do. >>> >>> Hmm, it say >>> >>> Names beginning with ``x-`` used to signify "experimental". This >>> convention has been replaced by special feature "unstable". >>> >>> "replaced".. So, I should use "unstable" flag without "x-" prefix? Can't >>> find an example. Seems "unstable" always used together with "x-". >> >> True. >> >> The "x-" prefix originated with qdev properties. First use might be >> commit f0c07c7c7b4. The convention wasn't documented then, but QOM/qdev >> properties have always been a documentation wasteland. It then spread >> to other places, and eventually to the QAPI schema. Where we try pretty >> hard to document things properly. We documented the "x-" prefix in >> commit e790e666518: >> >> Any name (command, event, type, field, or enum value) beginning with >> "x-" is marked experimental, and may be withdrawn or changed >> incompatibly in a future release. >> >> Minor pain point: when things grow up from experimental to stable, we >> have to rename. >> >> The convention didn't stop us from naming non-experimental things x-FOO, >> e.g. QOM property "x-origin" in commit 6105683da35. Made it to the QAPI >> schema in commit 8825587b53c. Point is: the prefix isn't a reliable >> marker for "unstable". >> >> Since I needed a reliable marker for my "set policy for unstable >> interfaces" feature (see CLI option -compat), I created special feature >> flag "unstable", and dropped the "x-" convention for the QAPI schema. >> >> Renaming existing "x-" names felt like pointless churn, so I didn't. >> >> I'm not objecting to new names starting with "x-". Nor am I objecting >> to feature 'unstable' on names that don't start with "x-". >> >> I guess "x-" remains just fine for things we don't intend to make stable >> at some point. The "x-" can remind humans "this is unstable" better >> than a feature flag can (for machines, it's the other way round). >> >> For things we do intend (hope?) to make stable, I wouldn't bother with >> the "x-". >> >> Clearer now? > > Yes, thanks. > > x- seems safer for management tool that doesn't know about "unstable" > properties..
Easy, traditional, and unreliable :) > But on the other hand, changing from x- to no-prefix is already done when the > feature is stable, and thouse who use it already use the latest version of > interface, so, removing the prefix is just extra work. Exactly. > So, I think, I'd go without prefix. Makes sense. >>> Also, nothing said about events. Is using "X_" wrong idea? Should it be >>> x-SOME_EVENT instead? >> >> Since this is the first unstable event, there is no precedent. Let's >> use no prefix, and move on. >> >>>> The name CONFIG_READ feels overly generic for something that makes sense >>>> only with virtio devices. >>> >>> Hmm, right.. I think, we can say same thing about DEVICE_UNPLUG_GUEST_ERROR. >> >> That one came to be as a generalization of existing MEM_UNPLUG_ERROR and >> a concrete need to signal CPU unplug errors. Demonstrates "unplug guest >> errors" can happen for different kinds of devices. So we went with a >> generic event we can use for all of them. >> This doesn't seem to be the case for this patch's event. Thoughts? > > Right.. VIRTIO_CONFIG_READ maybe? Works for me. [...]