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Date:   Tue, 10 Sep 2019 11:15:44 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To:     Lu Baolu <baolu.lu@linux.intel.com>
Cc:     David Woodhouse <dwmw2@infradead.org>,
        Joerg Roedel <joro@8bytes.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Christoph Hellwig <hch@lst.de>, ashok.raj@intel.com,
        jacob.jun.pan@intel.com, alan.cox@intel.com, kevin.tian@intel.com,
        mika.westerberg@linux.intel.com, Ingo Molnar <mingo@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        pengfei.xu@intel.com, Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v9 1/5] swiotlb: Split size parameter to map/unmap APIs
Message-ID: <20190910151544.GA7585@char.us.oracle.com>
References: <20190906061452.30791-1-baolu.lu@linux.intel.com>
 <20190906061452.30791-2-baolu.lu@linux.intel.com>
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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 <hch@lst.de>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> Reviewed-by: Christoph Hellwig <hch@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
>