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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id af79cd13be357-910bad2dd8esm2189342485a.19.2026.05.20.09.08.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2026 09:08:45 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wPjTQ-0000000HOo0-1ts3; Wed, 20 May 2026 13:08:44 -0300 Date: Wed, 20 May 2026 13:08:44 -0300 From: Jason Gunthorpe To: Jiri Pirko Cc: linux-rdma@vger.kernel.org, leon@kernel.org, edwards@nvidia.com, kees@kernel.org, parav@nvidia.com, mbloch@nvidia.com, yishaih@nvidia.com, lirongqing@baidu.com, huangjunxian6@hisilicon.com, liuy22@mails.tsinghua.edu.cn, jmoroni@google.com Subject: Re: [PATCH rdma-next v6 03/15] RDMA/core: Introduce generic buffer descriptor infrastructure for umem Message-ID: <20260520160844.GW7702@ziepe.ca> References: <20260520101129.899464-1-jiri@resnulli.us> <20260520101129.899464-4-jiri@resnulli.us> Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260520101129.899464-4-jiri@resnulli.us> On Wed, May 20, 2026 at 12:11:17PM +0200, Jiri Pirko wrote: > +int uverbs_attr_get_buffer_desc(const struct uverbs_attr_bundle *attrs, > + u16 attr_id, > + struct ib_uverbs_buffer_desc *desc) > +{ > + int ret; > + > + ret = uverbs_copy_from(desc, attrs, attr_id); > + if (ret) > + return ret; > + if (desc->reserved[0] || desc->reserved[1]) > + return -EINVAL; I'd like to carve out some space for optional kernel ignored flags here. Basically a flags field that kernel just ignores. If userspace requests a flag through this field that the kernel does not support it ignores the request and does nothing. Then a seperate flags that the kernel does enforce every set bit is understood. We've not included this a few times in the past and were sad about it.. I also want to think about how we can discover if the kernel supports this new path from userspace.. Jason