Stanislav Fomichev <sdf@xxxxxxxxxx> writes: > On Fri, Feb 17, 2023 at 9:55 AM Martin KaFai Lau <martin.lau@xxxxxxxxx> wrote: >> >> On 2/17/23 9:40 AM, Stanislav Fomichev wrote: >> > On Fri, Feb 17, 2023 at 9:39 AM Martin KaFai Lau <martin.lau@xxxxxxxxx> wrote: >> >> >> >> On 2/17/23 9:32 AM, Stanislav Fomichev wrote: >> >>> On 02/17, Jesper Dangaard Brouer wrote: >> >>>> With our XDP-hints kfunc approach, where individual drivers overload the >> >>>> default implementation, it can be hard for API users to determine >> >>>> whether or not the current device driver have this kfunc available. >> >>> >> >>>> Change the default implementations to use an errno (ENODEV), that >> >>>> drivers shouldn't return, to make it possible for BPF runtime to >> >>>> determine if bpf kfunc for xdp metadata isn't implemented by driver. >> >>> >> >>>> This is intended to ease supporting and troubleshooting setups. E.g. >> >>>> when users on mailing list report -19 (ENODEV) as an error, then we can >> >>>> immediately tell them their device driver is too old. >> >>> >> >>> I agree with the v1 comments that I'm not sure how it helps. >> >>> Why can't we update the doc in the same fashion and say that >> >>> the drivers shouldn't return EOPNOTSUPP? >> >>> >> >>> I'm fine with the change if you think it makes your/users life >> >>> easier. Although I don't really understand how. We can, as Toke >> >>> mentioned, ask the users to provide jited program dump if it's >> >>> mostly about user reports. >> >> >> >> and there is xdp-features also. >> > >> > Yeah, I was going to suggest it, but then I wasn't sure how to >> > reconcile our 'kfunc is not a uapi' with xdp-features (that probably >> > is a uapi)? >> >> uapi concern is a bit in xdp-features may go away because the kfunc may go away ? > > Yeah, if it's another kind of bitmask we'd have to retain those bits > (in case of a particular kfunc ever going away).. > >> May be a list of xdp kfunc names that it supports? A list of kfunc btf id will >> do also and the user space will need to map it back. Not sure if it is easily >> doable in xdp-features. > > Good point. A string list / btf_id list of kfuncs implemented by > netdev might be a good alternative. Yup, Lorenzo and I discussed something similar at one point, I think having this as part of the feature thing would be useful! -Toke
