Re: [PATCH 1/2] dma-direct: improve swiotlb error reporting

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, Feb 04, 2020 at 07:32:04AM +0100, Christoph Hellwig wrote:
> Untangle the way how dma_direct_map_page calls into swiotlb to be able
> to properly report errors where the swiotlb DMA address overflows the
> mask separately from overflows in the !swiotlb case.  This means that
> siotlb_map now has to do a little more work that duplicates
> dma_direct_map_page, but doing so greatly simplifies the calling
> convention.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Konrad Rzeszutek Wilk <konrad@darnok.org>

(Pick whichever tag you want :-))
> ---
>  include/linux/swiotlb.h | 11 +++--------
>  kernel/dma/direct.c     | 16 +++++++--------
>  kernel/dma/swiotlb.c    | 43 +++++++++++++++++++++++------------------
>  3 files changed, 34 insertions(+), 36 deletions(-)
> 
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index cde3dc18e21a..046bb94bd4d6 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -64,6 +64,9 @@ extern void swiotlb_tbl_sync_single(struct device *hwdev,
>  				    size_t size, enum dma_data_direction dir,
>  				    enum dma_sync_target target);
>  
> +dma_addr_t swiotlb_map(struct device *dev, phys_addr_t phys,
> +		size_t size, enum dma_data_direction dir, unsigned long attrs);
> +
>  #ifdef CONFIG_SWIOTLB
>  extern enum swiotlb_force swiotlb_force;
>  extern phys_addr_t io_tlb_start, io_tlb_end;
> @@ -73,8 +76,6 @@ static inline bool is_swiotlb_buffer(phys_addr_t paddr)
>  	return paddr >= io_tlb_start && paddr < io_tlb_end;
>  }
>  
> -bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
> -		size_t size, enum dma_data_direction dir, unsigned long attrs);
>  void __init swiotlb_exit(void);
>  unsigned int swiotlb_max_segment(void);
>  size_t swiotlb_max_mapping_size(struct device *dev);
> @@ -85,12 +86,6 @@ static inline bool is_swiotlb_buffer(phys_addr_t paddr)
>  {
>  	return false;
>  }
> -static inline bool swiotlb_map(struct device *dev, phys_addr_t *phys,
> -		dma_addr_t *dma_addr, size_t size, enum dma_data_direction dir,
> -		unsigned long attrs)
> -{
> -	return false;
> -}
>  static inline void swiotlb_exit(void)
>  {
>  }
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 6af7ae83c4ad..82ad50aaf42c 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -357,13 +357,6 @@ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
>  EXPORT_SYMBOL(dma_direct_unmap_sg);
>  #endif
>  
> -static inline bool dma_direct_possible(struct device *dev, dma_addr_t dma_addr,
> -		size_t size)
> -{
> -	return swiotlb_force != SWIOTLB_FORCE &&
> -		dma_capable(dev, dma_addr, size, true);
> -}
> -
>  dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
>  		unsigned long offset, size_t size, enum dma_data_direction dir,
>  		unsigned long attrs)
> @@ -371,8 +364,13 @@ dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
>  	phys_addr_t phys = page_to_phys(page) + offset;
>  	dma_addr_t dma_addr = phys_to_dma(dev, phys);
>  
> -	if (unlikely(!dma_direct_possible(dev, dma_addr, size)) &&
> -	    !swiotlb_map(dev, &phys, &dma_addr, size, dir, attrs)) {
> +	if (unlikely(swiotlb_force == SWIOTLB_FORCE))
> +		return swiotlb_map(dev, phys, size, dir, attrs);
> +
> +	if (unlikely(!dma_capable(dev, dma_addr, size, true))) {
> +		if (swiotlb_force != SWIOTLB_NO_FORCE)
> +			return swiotlb_map(dev, phys, size, dir, attrs);
> +
>  		report_addr(dev, dma_addr, size);
>  		return DMA_MAPPING_ERROR;
>  	}
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 9280d6f8271e..589bb9a40f21 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -22,6 +22,7 @@
>  
>  #include <linux/cache.h>
>  #include <linux/dma-direct.h>
> +#include <linux/dma-noncoherent.h>
>  #include <linux/mm.h>
>  #include <linux/export.h>
>  #include <linux/spinlock.h>
> @@ -656,35 +657,39 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
>  }
>  
>  /*
> - * Create a swiotlb mapping for the buffer at @phys, and in case of DMAing
> + * Create a swiotlb mapping for the buffer at @paddr, and in case of DMAing
>   * to the device copy the data into it as well.
>   */
> -bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
> -		size_t size, enum dma_data_direction dir, unsigned long attrs)
> +dma_addr_t swiotlb_map(struct device *dev, phys_addr_t paddr, size_t size,
> +		enum dma_data_direction dir, unsigned long attrs)
>  {
> -	trace_swiotlb_bounced(dev, *dma_addr, size, swiotlb_force);
> +	phys_addr_t swiotlb_addr;
> +	dma_addr_t dma_addr;
>  
> -	if (unlikely(swiotlb_force == SWIOTLB_NO_FORCE)) {
> -		dev_warn_ratelimited(dev,
> -			"Cannot do DMA to address %pa\n", phys);
> -		return false;
> -	}
> +	trace_swiotlb_bounced(dev, phys_to_dma(dev, paddr), size,
> +			      swiotlb_force);
>  
> -	/* 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, size, dir, attrs);
> -	if (*phys == (phys_addr_t)DMA_MAPPING_ERROR)
> -		return false;
> +	swiotlb_addr = swiotlb_tbl_map_single(dev,
> +			__phys_to_dma(dev, io_tlb_start),
> +			paddr, size, size, dir, attrs);
> +	if (swiotlb_addr == (phys_addr_t)DMA_MAPPING_ERROR)
> +		return DMA_MAPPING_ERROR;
>  
>  	/* Ensure that the address returned is DMA'ble */
> -	*dma_addr = __phys_to_dma(dev, *phys);
> -	if (unlikely(!dma_capable(dev, *dma_addr, size, true))) {
> -		swiotlb_tbl_unmap_single(dev, *phys, size, size, dir,
> +	dma_addr = __phys_to_dma(dev, swiotlb_addr);
> +	if (unlikely(!dma_capable(dev, dma_addr, size, true))) {
> +		swiotlb_tbl_unmap_single(dev, swiotlb_addr, size, size, dir,
>  			attrs | DMA_ATTR_SKIP_CPU_SYNC);
> -		return false;
> +		dev_err_once(dev,
> +			"swiotlb addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
> +			&dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
> +		WARN_ON_ONCE(1);
> +		return DMA_MAPPING_ERROR;
>  	}
>  
> -	return true;
> +	if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> +		arch_sync_dma_for_device(swiotlb_addr, size, dir);
> +	return dma_addr;
>  }
>  
>  size_t swiotlb_max_mapping_size(struct device *dev)
> -- 
> 2.24.1
> 
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