Mon, Aug 03, 2026 at 03:28:44PM +0200, [email protected] wrote: >On Mon, Aug 03, 2026 at 01:59:07PM +0200, Jiri Pirko wrote: >> Fri, Jul 31, 2026 at 02:54:31PM +0200, [email protected] wrote: >> >> From: Jiri Pirko <[email protected]> >> >> >> >> Commit eb70d83a8645 ("RDMA/mana_ib: Adopt robust udata") renamed the >> >> "flags" field of struct mana_ib_create_cq to "comp_mask", as >> >> ib_copy_validate_udata_in_cm() only validates a member with that name. >> >> >> >> The layout did not change, but the field has been a part of the UAPI since >> >> commit 44b607ad4cdf ("RDMA/mana_ib: implement uapi for creation of rnic >> >> cq"), so the rename breaks userspace referring to it, for example the mana >> >> provider of rdma-core assigning cmd_drv->flags. >> >> >> >> Convert the field to a union providing both names, so that >> >> ib_copy_validate_udata_in_cm() still finds "comp_mask" and userspace keeps >> >> "flags", without having to add a helper for this single case. >> >> >> > >> >Thanks for the patch, but my understanding that it is a common practice to >> >rename the fields, >> >and kernels headers should not accumulate historical names. >> >> That is not doable in UAPI. > >There are multiple levels of UAPI contracts. In RDMA, we guarantee >binary compatibility because userspace (rdma-core) is effectively the >second half of the RDMA driver stack. These drivers do not exist >without rdma-core. > >As such, this is exactly how the RDMA UAPI is intended to work.
That is some odd UAPI... > > >> Some userspace app, like rdma-core in this case, might use it and rename >> breaks the compilation. Some other >> app you don't know about may use it. > >rdma-core does not use these headers directly. Instead, it vendors >them in the kernel-headers directories specifically for this purpose. > >> >> >> >I also faced a similar problem from renames in other providers, when I >> >needed a new kernel header in rdma-core. >> >If this breaks your rdma-core in a PR, just remove the field rename in >> >kernel update commit as that header update commit is not getting merged >> >anyway from your PR. >> >My understanding that maintainers of RDMA-core will merge the kernel header >> >update, and will bring this change from my PR: >> >https://github.com/linux-rdma/rdma-core/pull/1765/commits/0dcadd9316f1b98e21973e3a6e0f96186d49bd5a >> >> this is not how UAPI can be changed :/ It simply can't be changed. > >It can, at least in RDMA and elsewhere in the kernel, where user >access is provided through properly designed libraries. Ehm, up to you. Very loose. > >Thanks > >> >> >> > >> >- Konstantin >> > >> >> Fixes: eb70d83a8645 ("RDMA/mana_ib: Adopt robust udata") >> >> Signed-off-by: Jiri Pirko <[email protected]> >> >> --- >> >> include/uapi/rdma/mana-abi.h | 5 ++++- >> >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> >> >> diff --git a/include/uapi/rdma/mana-abi.h b/include/uapi/rdma/mana-abi.h >> >> index 410f0ddc8c89..431c7076f20a 100644 >> >> --- a/include/uapi/rdma/mana-abi.h >> >> +++ b/include/uapi/rdma/mana-abi.h >> >> @@ -25,7 +25,10 @@ enum mana_ib_create_cq_flags { >> >> >> >> struct mana_ib_create_cq { >> >> __aligned_u64 buf_addr; >> >> - __u16 comp_mask; >> >> + union { >> >> + __u16 comp_mask; >> >> + __u16 flags; /* the original name of the field */ >> >> + }; >> >> __u16 reserved0; >> >> __u32 reserved1; >> >> }; >> >> -- >> >> 2.54.0 >> >
