linux-kernel - Re: [PATCH v2 00/10] iommu/vt-d: Bounce buffer for untrusted devices

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Date:   Thu, 28 Mar 2019 14:33:04 +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
Subject: Re: [PATCH v2 00/10] iommu/vt-d: Bounce buffer for untrusted devices

Hi,

On 3/27/19 2:48 PM, Christoph Hellwig wrote:
> On Wed, Mar 27, 2019 at 02:34:56PM +0800, Lu Baolu wrote:
>>    - During the v1 review cycle, we discussed the possibility
>>      of reusing swiotlb code to avoid code dumplication, but
>>      we found the swiotlb implementations are not ready for the
>>      use of bounce page pool.
>>      https://lkml.org/lkml/2019/3/19/259
> 
> So make it ready.  You too can contribute to common code.  Robin
> also explicitly asked to make the bounce policy iommu-subsystem wide.
> 

Sure. I am glad to make the code common. I will try to make it with a
new version.

For the swiotlb APIs, I am thinking about keeping current APIs untouched
and adding below new ones for bounce page.

/**
  * swiotlb_bounce_page_map - create a bounce page mapping
  * @dev: the device
  * @phys: the physical address of the buffer requiring bounce
  * @size: the size of the buffer
  * @align: IOMMU page align
  * @dir: DMA direction
  * @attrs: DMA attributions
  *
  * This creates a swiotlb bounce page mapping for the buffer at @phys,
  * and in case of DMAing to the device copy the data into it as well.
  * Return the tlb addr on success, otherwise DMA_MAPPING_ERROR.
  */
dma_addr_t
swiotlb_bounce_page_map(struct device *dev, phys_addr_t phys,
                         size_t size, unsigned long align,
                         enum dma_data_direction dir, unsigned long attrs)
{
         return 0;
}

/**
  * swiotlb_bounce_page_unmap - destroy a bounce page mapping
  * @dev: the device
  * @tlb_addr: the tlb address of the buffer requiring bounce
  * @size: the size of the buffer
  * @align: IOMMU page align
  * @dir: DMA direction
  * @attrs: DMA attributions
  *
  * This destroys a swiotlb bounce page mapping for the buffer at @tlb_addr,
  * and in case of DMAing from the device copy the data from it as well.
  */
void
swiotlb_bounce_page_unmap(struct device *dev, phys_addr_t tlb_addr,
                           size_t size, unsigned long align,
                           enum dma_data_direction dir, unsigned long attrs)
{
}

/**
  * swiotlb_bounce_page_sync - sync bounce page mapping
  * @dev: the device
  * @tlb_addr: the tlb address of the buffer requiring bounce
  * @size: the size of the buffer
  * @align: IOMMU page align
  * @dir: DMA direction
  * @attrs: DMA attributions
  *
  * This syncs a swiotlb bounce page mapping for the buffer at @tlb_addr.
  */
void
swiotlb_bounce_page_sync(struct device *dev, phys_addr_t tlb_addr,
                           size_t size, unsigned long align,
                           enum dma_data_direction dir, unsigned long attrs)
{
}

Any comments?

Best regards,
Lu Baolu