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b=wXDzlVcVNurKXmI6SG/zJxTyBDm+Eb9h6YkHbiPQuC9PpWhzQB2m6t4aVJCgd3GY4oivU7K8CsmVCzrsYnyDXZSYE9nurCb1VXJM0Yrl+YvvjPQwuigYG/7H0CjRWUFhX6VWWoT5po5g8mpMdTTi70Mc7jiHn/kLLj01PaZ8Hv8= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) by DM4PR12MB7720.namprd12.prod.outlook.com (2603:10b6:8:100::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9587.16; Mon, 9 Feb 2026 13:55:31 +0000 Received: from PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c]) by PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c%5]) with mapi id 15.20.9587.017; Mon, 9 Feb 2026 13:55:31 +0000 Message-ID: <9020b3cb-42e1-4c14-a748-c9a392d6f0be@amd.com> Date: Mon, 9 Feb 2026 14:55:26 +0100 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC] dmabuf backed read/write To: Jason Gunthorpe Cc: Pavel Begunkov , linux-block@vger.kernel.org, io-uring , "linux-nvme@lists.infradead.org" , "Gohad, Tushar" , Christoph Hellwig , Kanchan Joshi , Anuj Gupta , Nitesh Shetty , "lsf-pc@lists.linux-foundation.org" References: <20260205174135.GA444713@nvidia.com> <20260205235647.GA4177530@nvidia.com> <3281a845-a1b8-468c-a528-b9f6003cddea@gmail.com> <20260206152041.GA1874040@nvidia.com> <20260206183756.GB1874040@nvidia.com> <4736af5c-4bf8-4e9b-8f82-4b89a75d2cdb@gmail.com> <20260209130607.GF1874040@nvidia.com> <6246cc2b-0d6e-4062-ac24-74c7148dc47d@amd.com> <20260209132417.GA3076640@nvidia.com> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <20260209132417.GA3076640@nvidia.com> Content-Type: text/plain; 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I'm suggesting io_uring, and only io_uring could > use this with it fully implementing all the lifecycle rules that are > needed. Including move_notify and fences so that the driver managed > exporter has no issue. Yeah, that is basically what everybody currently does with out of tree code. The problem is that this requires internal knowledge of the exported buffer and how the I/O path is using it. So to generalize this for upstreaming it would need something like a giant whitelist of exporter/importer combinations which are known to work together and not crash the kernel in surprising and hard to track down ways. I had this conversation multiple times with both AMD internal as well as external people and just using an exporter specific io_uring (or whatever approach the exporter uses) implementation is just simpler. > Reworking the block stack to not rely on page is also a good path, but > probably alot harder. :\ Yeah, that would be really really nice to have and the latest patches for extending the struct file stuff actually looked quite promising. Christian. > > Jason