Re: [PATCH v13 06/12] swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 17 Jun 2021, Claire Chang wrote:
> Propagate the swiotlb_force into io_tlb_default_mem->force_bounce and
> use it to determine whether to bounce the data or not. This will be
> useful later to allow for different pools.
> 
> Signed-off-by: Claire Chang <tientzu@xxxxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Tested-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Tested-by: Will Deacon <will@xxxxxxxxxx>

Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  drivers/xen/swiotlb-xen.c |  2 +-
>  include/linux/swiotlb.h   | 11 +++++++++++
>  kernel/dma/direct.c       |  2 +-
>  kernel/dma/direct.h       |  2 +-
>  kernel/dma/swiotlb.c      |  4 ++++
>  5 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 0c6ed09f8513..4730a146fa35 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -369,7 +369,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device 
> *dev, struct page *page,
>       if (dma_capable(dev, dev_addr, size, true) &&
>           !range_straddles_page_boundary(phys, size) &&
>               !xen_arch_need_swiotlb(dev, phys, dev_addr) &&
> -             swiotlb_force != SWIOTLB_FORCE)
> +             !is_swiotlb_force_bounce(dev))
>               goto done;
>  
>       /*
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index dd1c30a83058..8d8855c77d9a 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -84,6 +84,7 @@ extern enum swiotlb_force swiotlb_force;
>   *           unmap calls.
>   * @debugfs: The dentry to debugfs.
>   * @late_alloc:      %true if allocated using the page allocator
> + * @force_bounce: %true if swiotlb bouncing is forced
>   */
>  struct io_tlb_mem {
>       phys_addr_t start;
> @@ -94,6 +95,7 @@ struct io_tlb_mem {
>       spinlock_t lock;
>       struct dentry *debugfs;
>       bool late_alloc;
> +     bool force_bounce;
>       struct io_tlb_slot {
>               phys_addr_t orig_addr;
>               size_t alloc_size;
> @@ -109,6 +111,11 @@ static inline bool is_swiotlb_buffer(struct device *dev, 
> phys_addr_t paddr)
>       return mem && paddr >= mem->start && paddr < mem->end;
>  }
>  
> +static inline bool is_swiotlb_force_bounce(struct device *dev)
> +{
> +     return dev->dma_io_tlb_mem->force_bounce;
> +}
> +
>  void __init swiotlb_exit(void);
>  unsigned int swiotlb_max_segment(void);
>  size_t swiotlb_max_mapping_size(struct device *dev);
> @@ -120,6 +127,10 @@ static inline bool is_swiotlb_buffer(struct device *dev, 
> phys_addr_t paddr)
>  {
>       return false;
>  }
> +static inline bool is_swiotlb_force_bounce(struct device *dev)
> +{
> +     return false;
> +}
>  static inline void swiotlb_exit(void)
>  {
>  }
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 7a88c34d0867..a92465b4eb12 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -496,7 +496,7 @@ size_t dma_direct_max_mapping_size(struct device *dev)
>  {
>       /* If SWIOTLB is active, use its maximum mapping size */
>       if (is_swiotlb_active(dev) &&
> -         (dma_addressing_limited(dev) || swiotlb_force == SWIOTLB_FORCE))
> +         (dma_addressing_limited(dev) || is_swiotlb_force_bounce(dev)))
>               return swiotlb_max_mapping_size(dev);
>       return SIZE_MAX;
>  }
> diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
> index 13e9e7158d94..4632b0f4f72e 100644
> --- a/kernel/dma/direct.h
> +++ b/kernel/dma/direct.h
> @@ -87,7 +87,7 @@ static inline dma_addr_t dma_direct_map_page(struct device 
> *dev,
>       phys_addr_t phys = page_to_phys(page) + offset;
>       dma_addr_t dma_addr = phys_to_dma(dev, phys);
>  
> -     if (unlikely(swiotlb_force == SWIOTLB_FORCE))
> +     if (is_swiotlb_force_bounce(dev))
>               return swiotlb_map(dev, phys, size, dir, attrs);
>  
>       if (unlikely(!dma_capable(dev, dma_addr, size, true))) {
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 409694d7a8ad..13891d5de8c9 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -179,6 +179,10 @@ static void swiotlb_init_io_tlb_mem(struct io_tlb_mem 
> *mem, phys_addr_t start,
>       mem->end = mem->start + bytes;
>       mem->index = 0;
>       mem->late_alloc = late_alloc;
> +
> +     if (swiotlb_force == SWIOTLB_FORCE)
> +             mem->force_bounce = true;
> +
>       spin_lock_init(&mem->lock);
>       for (i = 0; i < mem->nslabs; i++) {
>               mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
> -- 
> 2.32.0.288.g62a8d224e6-goog
>