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

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Message-ID: <c9fe7879-569e-b4f4-d6ec-47ab7e6fd443@linux.intel.com>
Date:   Wed, 13 Mar 2019 10:31:52 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     baolu.lu@...ux.intel.com, 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

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?

Best regards,
Lu Baolu

> 
> I don't think we are doing the same thing as swiotlb here. But it's
> always a good thing to reuse code if possible. I considered this when
> writing this code, but I found it's hard to do. Do you mind pointing
> me to the code which I could reuse?
> 
> Best regards,
> Lu Baolu
>