On Sun, Sep 11, 2016 at 11:14:09AM -0600, Jason Gunthorpe wrote: > > > We stil always have the common structure first. And at least for > > > cgroups supports that's what matters. > > > > > > Re the actual structures - we'll really need to make sure we > > > > > > a) expose proper userspace abi headers in the kernel for all code > > > in the RDMA subsystem > > > b) actually use that in the userspace components > > > > > > I've posted some initial work toward a) a while ago, and once we > > Did it get merged? Do you have a pointer? http://www.spinics.net/lists/linux-rdma/msg31958.html > this without it would be very hard, as everything is cross-linked, I > couldnn't unwind libibcm until I fixed a bit of verbs, and rdmacm can't > even include its uapi header until the duplicate definitions in the > verbs copy are delt with .. and I've also learned we are making > changing to the kernel uapi header and since nothing uses them we never even > compile test :( :( eg > https://github.com/torvalds/linux/commit/b493d91d333e867a043f7ff1397bcba6e2d0dda2] > However, everything under verbs is not straightforward. The files in > userspace are not copies... > > user: > > struct ibv_query_device { > __u32 command; > __u16 in_words; > __u16 out_words; > __u64 response; > __u64 driver_data[0]; > }; > > kernel: > > struct ib_uverbs_query_device { > __u64 response; > __u64 driver_data[0]; > }; We'll obviously need different strutures for the libibvers API and the kernel interface in this case, and we'll need to figure out how to properly translate them. I think a cast, plus compile time type checking ala BUILD_BUG_ON is the way to go. > eg the userspace version stuffs the header into the struct and the > kernel version does not. Presumably this is for efficiency so that no > copies are required when marshaling. This impacts everything :( > > I'm thinking the best way forward might be to use a script and > transform userspace into: > > struct ibv_query_device { > struct ib_uverbs_cmd_hdr hdr; > struct ib_uverbs_query_device cmd; > }; That would break the users of the interface. However automatically generating the user ABI from the kernel one might still be a good idea in the long run. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
