On Fri, Sep 06, 2019 at 02:14:48PM +0800, Lu Baolu wrote:
> This splits the size parameter to swiotlb_tbl_map_single() and
> swiotlb_tbl_unmap_single() into an alloc_size and a mapping_size
> parameter, where the latter one is rounded up to the iommu page
> size.

It does a bit more too. You have the WARN_ON. Can you make it be
more  verbose (as in details of which device requested it) and also use 
printk_once or so please?
> 
> Suggested-by: Christoph Hellwig <h...@lst.de>
> Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
> Reviewed-by: Christoph Hellwig <h...@lst.de>
> ---
>  drivers/xen/swiotlb-xen.c |  8 ++++----
>  include/linux/swiotlb.h   |  8 ++++++--
>  kernel/dma/direct.c       |  2 +-
>  kernel/dma/swiotlb.c      | 30 +++++++++++++++++++-----------
>  4 files changed, 30 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index ae1df496bf38..adcabd9473eb 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -386,8 +386,8 @@ static dma_addr_t xen_swiotlb_map_page(struct device 
> *dev, struct page *page,
>        */
>       trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);
>  
> -     map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir,
> -                                  attrs);
> +     map = swiotlb_tbl_map_single(dev, start_dma_addr, phys,
> +                                  size, size, dir, attrs);
>       if (map == (phys_addr_t)DMA_MAPPING_ERROR)
>               return DMA_MAPPING_ERROR;
>  
> @@ -397,7 +397,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device 
> *dev, struct page *page,
>        * Ensure that the address returned is DMA'ble
>        */
>       if (unlikely(!dma_capable(dev, dev_addr, size))) {
> -             swiotlb_tbl_unmap_single(dev, map, size, dir,
> +             swiotlb_tbl_unmap_single(dev, map, size, size, dir,
>                               attrs | DMA_ATTR_SKIP_CPU_SYNC);
>               return DMA_MAPPING_ERROR;
>       }
> @@ -433,7 +433,7 @@ static void xen_unmap_single(struct device *hwdev, 
> dma_addr_t dev_addr,
>  
>       /* NOTE: We use dev_addr here, not paddr! */
>       if (is_xen_swiotlb_buffer(dev_addr))
> -             swiotlb_tbl_unmap_single(hwdev, paddr, size, dir, attrs);
> +             swiotlb_tbl_unmap_single(hwdev, paddr, size, size, dir, attrs);
>  }
>  
>  static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index 361f62bb4a8e..cde3dc18e21a 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -46,13 +46,17 @@ enum dma_sync_target {
>  
>  extern phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
>                                         dma_addr_t tbl_dma_addr,
> -                                       phys_addr_t phys, size_t size,
> +                                       phys_addr_t phys,
> +                                       size_t mapping_size,
> +                                       size_t alloc_size,
>                                         enum dma_data_direction dir,
>                                         unsigned long attrs);
>  
>  extern void swiotlb_tbl_unmap_single(struct device *hwdev,
>                                    phys_addr_t tlb_addr,
> -                                  size_t size, enum dma_data_direction dir,
> +                                  size_t mapping_size,
> +                                  size_t alloc_size,
> +                                  enum dma_data_direction dir,
>                                    unsigned long attrs);
>  
>  extern void swiotlb_tbl_sync_single(struct device *hwdev,
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 706113c6bebc..8402b29c280f 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -305,7 +305,7 @@ void dma_direct_unmap_page(struct device *dev, dma_addr_t 
> addr,
>               dma_direct_sync_single_for_cpu(dev, addr, size, dir);
>  
>       if (unlikely(is_swiotlb_buffer(phys)))
> -             swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
> +             swiotlb_tbl_unmap_single(dev, phys, size, size, dir, attrs);
>  }
>  EXPORT_SYMBOL(dma_direct_unmap_page);
>  
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 9de232229063..89066efa3840 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -444,7 +444,9 @@ static void swiotlb_bounce(phys_addr_t orig_addr, 
> phys_addr_t tlb_addr,
>  
>  phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
>                                  dma_addr_t tbl_dma_addr,
> -                                phys_addr_t orig_addr, size_t size,
> +                                phys_addr_t orig_addr,
> +                                size_t mapping_size,
> +                                size_t alloc_size,
>                                  enum dma_data_direction dir,
>                                  unsigned long attrs)
>  {
> @@ -464,6 +466,9 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
>               pr_warn_once("%s is active and system is using DMA bounce 
> buffers\n",
>                            sme_active() ? "SME" : "SEV");
>  
> +     if (WARN_ON(mapping_size > alloc_size))
> +             return (phys_addr_t)DMA_MAPPING_ERROR;
> +
>       mask = dma_get_seg_boundary(hwdev);
>  
>       tbl_dma_addr &= mask;
> @@ -481,8 +486,8 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
>        * For mappings greater than or equal to a page, we limit the stride
>        * (and hence alignment) to a page size.
>        */
> -     nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
> -     if (size >= PAGE_SIZE)
> +     nslots = ALIGN(alloc_size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
> +     if (alloc_size >= PAGE_SIZE)
>               stride = (1 << (PAGE_SHIFT - IO_TLB_SHIFT));
>       else
>               stride = 1;
> @@ -547,7 +552,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
>       spin_unlock_irqrestore(&io_tlb_lock, flags);
>       if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit())
>               dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes), total 
> %lu (slots), used %lu (slots)\n",
> -                      size, io_tlb_nslabs, tmp_io_tlb_used);
> +                      alloc_size, io_tlb_nslabs, tmp_io_tlb_used);
>       return (phys_addr_t)DMA_MAPPING_ERROR;
>  found:
>       io_tlb_used += nslots;
> @@ -562,7 +567,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
>               io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT);
>       if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
>           (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
> -             swiotlb_bounce(orig_addr, tlb_addr, size, DMA_TO_DEVICE);
> +             swiotlb_bounce(orig_addr, tlb_addr, mapping_size, 
> DMA_TO_DEVICE);
>  
>       return tlb_addr;
>  }
> @@ -571,21 +576,24 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
>   * tlb_addr is the physical address of the bounce buffer to unmap.
>   */
>  void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
> -                           size_t size, enum dma_data_direction dir,
> -                           unsigned long attrs)
> +                           size_t mapping_size, size_t alloc_size,
> +                           enum dma_data_direction dir, unsigned long attrs)
>  {
>       unsigned long flags;
> -     int i, count, nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
> +     int i, count, nslots = ALIGN(alloc_size, 1 << IO_TLB_SHIFT) >> 
> IO_TLB_SHIFT;
>       int index = (tlb_addr - io_tlb_start) >> IO_TLB_SHIFT;
>       phys_addr_t orig_addr = io_tlb_orig_addr[index];
>  
> +     if (WARN_ON(mapping_size > alloc_size))
> +             return;
> +
>       /*
>        * First, sync the memory before unmapping the entry
>        */
>       if (orig_addr != INVALID_PHYS_ADDR &&
>           !(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
>           ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL)))
> -             swiotlb_bounce(orig_addr, tlb_addr, size, DMA_FROM_DEVICE);
> +             swiotlb_bounce(orig_addr, tlb_addr, mapping_size, 
> DMA_FROM_DEVICE);
>  
>       /*
>        * Return the buffer to the free list by setting the corresponding
> @@ -665,14 +673,14 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, 
> dma_addr_t *dma_addr,
>  
>       /* Oh well, have to allocate and map a bounce buffer. */
>       *phys = swiotlb_tbl_map_single(dev, __phys_to_dma(dev, io_tlb_start),
> -                     *phys, size, dir, attrs);
> +                     *phys, size, size, dir, attrs);
>       if (*phys == (phys_addr_t)DMA_MAPPING_ERROR)
>               return false;
>  
>       /* Ensure that the address returned is DMA'ble */
>       *dma_addr = __phys_to_dma(dev, *phys);
>       if (unlikely(!dma_capable(dev, *dma_addr, size))) {
> -             swiotlb_tbl_unmap_single(dev, *phys, size, dir,
> +             swiotlb_tbl_unmap_single(dev, *phys, size, size, dir,
>                       attrs | DMA_ATTR_SKIP_CPU_SYNC);
>               return false;
>       }
> -- 
> 2.17.1
> 

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