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 5CF89C54FB9 for ; Thu, 16 Nov 2023 11:10:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345086AbjKPLKZ (ORCPT ); Thu, 16 Nov 2023 06:10:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230464AbjKPLKN (ORCPT ); Thu, 16 Nov 2023 06:10:13 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD8641991; Thu, 16 Nov 2023 03:10:04 -0800 (PST) Received: from dggpemm500005.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4SWHKX3FJ1zsR46; Thu, 16 Nov 2023 19:06:40 +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 19:10:01 +0800 Subject: Re: [PATCH RFC 3/8] memory-provider: dmabuf devmem memory provider To: Jason Gunthorpe CC: Mina Almasry , 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: <0a1cdd5a-c4c5-3d77-20a2-2beb8e3a6411@huawei.com> Date: Thu, 16 Nov 2023 19:10:01 +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: dggems704-chm.china.huawei.com (10.3.19.181) 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 2023/11/15 21:38, Jason Gunthorpe wrote: > On Wed, Nov 15, 2023 at 05:21:02PM +0800, Yunsheng Lin wrote: > >>>>> I would expect net stack, page pool, driver still see the 'struct page', >>>>> only memory provider see the specific struct for itself, for the above, >>>>> devmem memory provider sees the 'struct page_pool_iov'. >>>>> >>>>> The reason I still expect driver to see the 'struct page' is that driver >>>>> will still need to support normal memory besides devmem. >>> >>> I wouldn't say this approach is unreasonable, but it does have to be >>> done carefully to isolate the mm. Keeping the struct page in the API >>> is going to make this very hard. >> >> I would expect that most of the isolation is done in page pool, as far as >> I can see: > > It is the sort of thing that is important enough it should have > compiler help via types to prove that it is being done > properly. Otherwise it will be full of mistakes over time. Yes, agreed. I have done something similar as willy has done for some of folio conversion as below: +#define PAGE_POOL_MATCH(pg, iov) \ + static_assert(offsetof(struct page, pg) == \ + offsetof(struct page_pool_iov, iov)) +PAGE_POOL_MATCH(flags, res0); +PAGE_POOL_MATCH(pp_magic, pp_magic); +PAGE_POOL_MATCH(pp, pp); ... Not sure if we need to add new API for driver to use when the driver need the devmem support yet. > > Jason > . >