linux-kernel - Re: [PATCH for-next 2/4] RDMA/hns: Add IOMMU enable support in hip08

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Message-ID: <5A03AEC3.10109@huawei.com>
Date:   Thu, 9 Nov 2017 09:26:27 +0800
From:   "Wei Hu (Xavier)" <xavier.huwei@...wei.com>
To:     Christoph Hellwig <hch@...radead.org>,
        Jason Gunthorpe <jgg@...pe.ca>
CC:     Robin Murphy <robin.murphy@....com>,
        Leon Romanovsky <leon@...nel.org>, <shaobo.xu@...el.com>,
        <xavier.huwei@....com>, <lijun_nudt@....com>, <oulijun@...wei.com>,
        <linux-rdma@...r.kernel.org>, <charles.chenxin@...wei.com>,
        <linuxarm@...wei.com>, <iommu@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <dledford@...hat.com>, <liuyixian@...wei.com>,
        <zhangxiping3@...wei.com>, <shaoboxu@....com>
Subject: Re: [PATCH for-next 2/4] RDMA/hns: Add IOMMU enable support in hip08



On 2017/11/7 23:58, Christoph Hellwig wrote:
> On Tue, Nov 07, 2017 at 08:48:38AM -0700, Jason Gunthorpe wrote:
>> Can't you just use vmalloc and dma_map that? Other drivers follow that
>> approach..
> You can't easily due to the flushing requirements.  We used to do that
> in XFS and it led to problems.  You need the page allocator + vmap +
> invalidate_kernel_vmap_range + flush_kernel_vmap_range to get the
> cache flushing right.
>
> .
Hi, Christoph Hellwig
    Thanks for your suggestion.
    Regards
Wei Hu