linux-kernel - Re: [PATCH v1 4/9] iommu/vt-d: Add bounce buffer API for domain map/unmap

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Date:   Wed, 13 Mar 2019 09:10:29 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>, ashok.raj@...el.com,
        jacob.jun.pan@...el.com, alan.cox@...el.com, kevin.tian@...el.com,
        mika.westerberg@...ux.intel.com, pengfei.xu@...el.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [PATCH v1 4/9] iommu/vt-d: Add bounce buffer API for domain
 map/unmap

On Wed, Mar 13, 2019 at 10:31:52AM +0800, Lu Baolu wrote:
> Hi again,
> 
> On 3/13/19 10:04 AM, Lu Baolu wrote:
> > Hi,
> > 
> > On 3/13/19 12:38 AM, Christoph Hellwig wrote:
> > > On Tue, Mar 12, 2019 at 02:00:00PM +0800, Lu Baolu wrote:
> > > > This adds the APIs for bounce buffer specified domain
> > > > map() and unmap(). The start and end partial pages will
> > > > be mapped with bounce buffered pages instead. This will
> > > > enhance the security of DMA buffer by isolating the DMA
> > > > attacks from malicious devices.
> > > 
> > > Please reuse the swiotlb code instead of reinventing it.
> > > 
> 
> Just looked into the code again. At least we could reuse below
> functions:
> 
> swiotlb_tbl_map_single()
> swiotlb_tbl_unmap_single()
> swiotlb_tbl_sync_single()
> 
> Anything else?

Yes, that is probably about the level you want to reuse, given that the
next higher layer already has hooks into the direct mapping code.