Re: [PATCH rdma-next v2 4/6] RDMA/uverbs: Add ioctl method for CQ resize

[Leon Romanovsky <leon@kernel.org>]

On Thu, Jun 18, 2026 at 11:40:29AM -0400, Dennis Dalessandro wrote:
> On 6/17/26 7:06 AM, Leon Romanovsky wrote:
> > On Mon, Jun 15, 2026 at 10:50:38AM +0200, Jiri Pirko wrote:
> > > From: Jiri Pirko <jiri@nvidia.com>
> > > 
> > > Resize CQ is currently only reachable through the legacy write()
> > > uverbs command (IB_USER_VERBS_CMD_RESIZE_CQ). Add an equivalent modern
> > > ioctl method, UVERBS_METHOD_CQ_RESIZE, on the CQ object so the
> > > operation is available through the ioctl interface and can carry
> > > per-attribute extensions. The handler mirrors the legacy command: it
> > > looks up the CQ, calls resize_user_cq() and returns the new cqe count.
> > > The legacy write path is left in place for ABI compatibility.
> > 
> > I have a general question. Do we actually need CQ resizing, given that it is
> > rarely implemented and often incorrect in existing drivers? Maybe this is a
> > good time to consider deprecating that path.
> 
> Can you expand on what you mean by incorrect in existing drivers? I mean I
> see a glaring coding bug in our implementation but I can patch that.

I had "create/resize CQ" series which fixed locking in all .resize_user_cq()
implementations. The series stalled to give Jiri some space with his umem work.

Part of that series can be found here: https://git.kernel.org/pub/scm/linux/kernel/git/leon/linux-rdma.git/commit/?h=create-cq-entries-v1&id=c4f7b5999b4015609481657b437a92346a018d2c

Thanks

> 
> -Denny
> 
>