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

[Lu Baolu]

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