From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70B87C197A0 for ; Thu, 16 Nov 2023 11:12:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345097AbjKPLMk (ORCPT ); Thu, 16 Nov 2023 06:12:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345003AbjKPLMi (ORCPT ); Thu, 16 Nov 2023 06:12:38 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9AD3DAA; Thu, 16 Nov 2023 03:12:35 -0800 (PST) Received: from dggpemm500005.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4SWHS01cx5zvQpM; Thu, 16 Nov 2023 19:12:16 +0800 (CST) Received: from [10.69.30.204] (10.69.30.204) by dggpemm500005.china.huawei.com (7.185.36.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Thu, 16 Nov 2023 19:12:33 +0800 Subject: Re: [PATCH RFC 3/8] memory-provider: dmabuf devmem memory provider To: David Ahern , Jason Gunthorpe , Mina Almasry CC: Jakub Kicinski , , , , , Willem de Bruijn , Kaiyuan Zhang , Jesper Dangaard Brouer , Ilias Apalodimas , Eric Dumazet , =?UTF-8?Q?Christian_K=c3=b6nig?= , Matthew Wilcox , Linux-MM References: <20231113130041.58124-1-linyunsheng@huawei.com> <20231113130041.58124-4-linyunsheng@huawei.com> <20231113180554.1d1c6b1a@kernel.org> <0c39bd57-5d67-3255-9da2-3f3194ee5a66@huawei.com> From: Yunsheng Lin Message-ID: <15c404e4-8efa-cc1c-174f-0752005b6755@huawei.com> Date: Thu, 16 Nov 2023 19:12:33 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.69.30.204] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm500005.china.huawei.com (7.185.36.74) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/11/16 1:57, David Ahern wrote: > On 11/15/23 2:21 AM, Yunsheng Lin wrote: >> On 2023/11/14 21:16, Jason Gunthorpe wrote: >>> On Tue, Nov 14, 2023 at 04:21:26AM -0800, Mina Almasry wrote: >>> >>>> Actually because you put the 'strtuct page for devmem' in >>>> skb->bv_frag, the net stack will grab the 'struct page' for devmem >>>> using skb_frag_page() then call things like page_address(), kmap, >>>> get_page, put_page, etc, etc, etc. >>> >>> Yikes, please no. If net has its own struct page look alike it has to >>> stay entirely inside net. A non-mm owned struct page should not be >>> passed into mm calls. It is just way too hacky to be seriously >>> considered :( >> >> Yes, that is something this patchset is trying to do, defining its own >> struct page look alike for page pool to support devmem. >> > > Networking needs to be able to move away from struct page references. > The devmem and host memory for Rx use cases do not need to be page based. Yes, I am agreed the ultimate goal is to move away from struct page references. But I am not sure if we can do it right away as there still are different types of existing 'struct page' in the netstack, see: https://lore.kernel.org/all/8b7d25eb-1f10-3e37-8753-92b42da3fb34@huawei.com/ > > > . >