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Subject: Re: [virtio] [PATCH v4] conformance: clarify transitional/non-transitional
On Thu, Mar 14, 2019 at 07:06:17PM +0100, Halil Pasic wrote: > On Thu, 14 Mar 2019 07:06:07 -0400 > "Michael S. Tsirkin" <mst@redhat.com> wrote: > > > On Wed, Mar 13, 2019 at 01:08:36PM +0100, Halil Pasic wrote: > > > On Tue, 12 Mar 2019 21:48:13 -0400 > > > "Michael S. Tsirkin" <mst@redhat.com> wrote: > > > > > > > We already have a specification for conformance targets for > > > > non-transitional devices. > > > > Just add another clause that transitional devices satisfy. > > > > > > > > VIRTIO-167 > > > > > > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > > > --- > [..] > > > > > > Hm, I actually liked that v3 spelled out, that legacy is not > > > standardized (no normative exists). > > > > Right but then I started worrying that > > - this was not actually what the defect report said. > > it was basically just complaining that this chapter was not > > linked into any conformance targets. > > I think whether legacy is a normative or a non-normative part of the > virtio spec is what we need to decide on in the first place. I agree it's a defect that it's unclear but I do not feel that we need to decide this at this point in time before 1.1. > If it is normative it needs to get linked to some conformance targets. > If it isn't normative, it should not be a part of the conformance > chapter. > > I think the latter is closer to how we as a community see this, but I'm > not sure. > > In any case if we decide legacy is normative then we need to change "7.1 > Conformance Targets" or change the conformance statements. > > Let me explain. Currently we have the conformance targets "driver" > and "device". We would need to change this to something like > "non-transitional driver", "transitional driver", "non-transitional > device" and "non-transitional device" if we decide to change the targets, > or declare that there is a variable e.g. called 'transitional' which may > take the values 'transitional' and 'non-transitional'. But then we would > need to convert the 'Legacy Interface' sections to 'if transitional > has the value transitional' parts of the respective normative statements. > > In any case making legacy interface a normative part of the spec requires > IMHO more work than this patch does. > > > > so it's an unrelated concern - why not defer it to 1.2? > > I'm all for deferring VIRTIO-167. OK before we do this let me try one more time, with a minimally invasive change. > > - can one argue that this is a material change? > > we don't want to come up with these at this stage > > I would argue that making legacy interface a normative part of the spec > is a material change. > > > - we actually specified quite a lot about legacy interfaces. > > so since we did the work already, why through it away? > > > > IMHO we should not throw it away. But we should make the form suit the > intention. The intention of the conformance targets of virtio > specification is a standard that guarantees conforming > implementations are interoperable. > > The intention behind the description of the legacy interface is not to > standardize it, but to help people cope with the virtio stuff that > emerged before virtio 1.0. > > > > v4 makes things look like > > > 'transitional' is a separate conformance profile, and that the > > > description of the legacy interface is normative. > > > > > > I think it kind of is, isn't it? > > > > The blurb of your v3 states the opposite: > """ > ... legacy device descriptions are non-normative. > In fact virtio 0.9 is non-normative as a whole > and always was by design: it was early days and > spec evolved to document bugs in implementations. > """ > > And I believe this is the truth. We certainly can make legacy interface > normative, but then we need to take care of the formal requirements. > > I see no benefit in making the legacy interface normative, because > AFAIU we don't expect legacy implementations to get fixed if they don't > conform to what is written in 'Legacy Interface'. AFAIU this is about > helping people to deal with legacy, but not about claims that something > is compliant to the legacy profile. > > > > > I took the liberty and tweaked your v3. As stated before, I don't think > > > transitional vs non-transitional is a big issue. I'm basically fine with > > > anything. > > > > > > Regards, > > > Halil > > > > Yea me too. For reasons above I prefer the more limited change in v4. > > But if you prefer pls post your version separately as a patch and we > > can have the TC choose by a ballot. > > > > I've just sent out a modified version of it. It ain't perfect. As said > before my preferred course of action would be: > * defer resolving VIRTIO-167 > * figure out how do we want to resolve VIRTIO-167 by figuring out do we > want to have a normative description of the legacy interface or not > * figure out how to change the spec accordingly (remove legacy form > conformance; or add a variable or add more conformance targets that > cover legacy) > > Cheers, > Halil > > [..]
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