From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 23B1D440460 for ; Wed, 8 Nov 2017 20:30:38 -0500 (EST) Received: by mail-pg0-f70.google.com with SMTP id p9so4464027pgc.6 for ; Wed, 08 Nov 2017 17:30:38 -0800 (PST) Received: from szxga04-in.huawei.com (szxga04-in.huawei.com. [45.249.212.190]) by mx.google.com with ESMTPS id k6si4832192pgq.102.2017.11.08.17.30.36 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 08 Nov 2017 17:30:37 -0800 (PST) Subject: Re: [PATCH for-next 2/4] RDMA/hns: Add IOMMU enable support in hip08 References: <1506763741-81429-1-git-send-email-xavier.huwei@huawei.com> <1506763741-81429-3-git-send-email-xavier.huwei@huawei.com> <20170930161023.GI2965@mtr-leonro.local> <59DF60A3.7080803@huawei.com> <5fe5f9b9-2c2b-ab3c-dafa-3e2add051bbb@arm.com> <59F97BBE.5070207@huawei.com> <5A011E49.6060407@huawei.com> <20171107154838.GC21466@ziepe.ca> From: "Wei Hu (Xavier)" Message-ID: <5A03AFA0.5090505@huawei.com> Date: Thu, 9 Nov 2017 09:30:08 +0800 MIME-Version: 1.0 In-Reply-To: <20171107154838.GC21466@ziepe.ca> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jason Gunthorpe Cc: Robin Murphy , Leon Romanovsky , shaobo.xu@intel.com, xavier.huwei@tom.com, lijun_nudt@163.com, oulijun@huawei.com, linux-rdma@vger.kernel.org, charles.chenxin@huawei.com, linuxarm@huawei.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, dledford@redhat.com, liuyixian@huawei.com, zhangxiping3@huawei.com, shaoboxu@tom.com On 2017/11/7 23:48, Jason Gunthorpe wrote: > On Tue, Nov 07, 2017 at 10:45:29AM +0800, Wei Hu (Xavier) wrote: > >> We reconstruct the code as below: >> It replaces dma_alloc_coherent with __get_free_pages and >> dma_map_single functions. So, we can vmap serveral ptrs returned by >> __get_free_pages, right? > Can't you just use vmalloc and dma_map that? Other drivers follow that > approach.. > > However, dma_alloc_coherent and dma_map_single are not the same > thing. You can't touch the vmap memory once you call dma_map unless > the driver also includes dma cache flushing calls in all the right > places. > > The difference is that alloc_coherent will return non-cachable memory > if necessary, while get_free_pages does not. > > Jason Hi, Jason Thanks for your suggestion. We will fix it. Regards Wei Hu > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org