Re: [PATCH v5 12/13] swiotlb-xen: use xen_alloc/free_coherent_pages

[Konrad Rzeszutek Wilk]

On Thu, Aug 29, 2013 at 07:32:33PM +0100, Stefano Stabellini wrote:
> Use xen_alloc_coherent_pages and xen_free_coherent_pages to allocate or
> free coherent pages.
> 
> We need to be careful handling the pointer returned by
> xen_alloc_coherent_pages, because on ARM the pointer is not equal to
> phys_to_virt(*dma_handle). In fact virt_to_phys on the returned pointer
> doesn't return a valid physical address.

Why is it called 'virt_to_phys'? What does it return then?

> 
> Make xen_create_contiguous_region take a phys_addr_t as start parameter to
> avoid the virt_to_phys calls which would be incorrect.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> ---
>  arch/arm/xen/mm.c         |    7 +++----
>  arch/x86/xen/mmu.c        |    7 +++++--
>  drivers/xen/swiotlb-xen.c |   24 +++++++++++++++---------
>  include/xen/xen-ops.h     |    4 ++--
>  4 files changed, 25 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
> index 1477ace..9163d4c 100644
> --- a/arch/arm/xen/mm.c
> +++ b/arch/arm/xen/mm.c
> @@ -55,11 +55,10 @@ static int xen_exchange_memory(xen_ulong_t extents_in,
>  	return success;
>  }
>  
> -int xen_create_contiguous_region(unsigned long vstart, unsigned int order,
> +int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
>  				 unsigned int address_bits,
>  				 dma_addr_t *dma_handle)
>  {
> -	phys_addr_t pstart = __pa(vstart);
>  	xen_pfn_t in_frame, out_frame;
>  	int success;
>  
> @@ -78,9 +77,9 @@ int xen_create_contiguous_region(unsigned long vstart, unsigned int order,
>  }
>  EXPORT_SYMBOL_GPL(xen_create_contiguous_region);
>  
> -void xen_destroy_contiguous_region(unsigned long vstart, unsigned int order)
> +void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
>  {
> -	xen_pfn_t in_frame = __pa(vstart) >> PAGE_SHIFT;
> +	xen_pfn_t in_frame = pstart >> PAGE_SHIFT;
>  	struct xen_unpin unpin = {
>  		.in = {
>  			.nr_extents   = 1,
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index 6c34d7c..07ee0e8 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -2328,13 +2328,14 @@ static int xen_exchange_memory(unsigned long extents_in, unsigned int order_in,
>  	return success;
>  }
>  
> -int xen_create_contiguous_region(unsigned long vstart, unsigned int order,
> +int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
>  				 unsigned int address_bits,
>  				 dma_addr_t *dma_handle)
>  {
>  	unsigned long *in_frames = discontig_frames, out_frame;
>  	unsigned long  flags;
>  	int            success;
> +	unsigned long vstart = (unsigned long) phys_to_virt(pstart);

Extra space.
>  
>  	/*
>  	 * Currently an auto-translated guest will not perform I/O, nor will
> @@ -2374,11 +2375,12 @@ int xen_create_contiguous_region(unsigned long vstart, unsigned int order,
>  }
>  EXPORT_SYMBOL_GPL(xen_create_contiguous_region);
>  
> -void xen_destroy_contiguous_region(unsigned long vstart, unsigned int order)
> +void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
>  {
>  	unsigned long *out_frames = discontig_frames, in_frame;
>  	unsigned long  flags;
>  	int success;
> +	unsigned long vstart;
>  
>  	if (xen_feature(XENFEAT_auto_translated_physmap))
>  		return;
> @@ -2386,6 +2388,7 @@ void xen_destroy_contiguous_region(unsigned long vstart, unsigned int order)
>  	if (unlikely(order > MAX_CONTIG_ORDER))
>  		return;
>  
> +	vstart = (unsigned long) phys_to_virt(pstart);

Ditto
>  	memset((void *) vstart, 0, PAGE_SIZE << order);
>  
>  	spin_lock_irqsave(&xen_reservation_lock, flags);
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 010da31..c96b928 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -46,6 +46,7 @@
>  #include <xen/hvc-console.h>
>  #include <xen/features.h>
>  #include <asm/dma-mapping.h>
> +#include <asm/xen/page-coherent.h>
>  
>  /*
>   * Used to do a quick range check in swiotlb_tbl_unmap_single and
> @@ -244,6 +245,7 @@ xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs)
>  {
>  	int i, j, rc;
>  	int dma_bits;
> +	phys_addr_t p = virt_to_phys(buf);
>  
>  	dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;
>  
> @@ -253,7 +255,7 @@ xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs)
>  
>  		do {
>  			rc = xen_create_contiguous_region(
> -				(unsigned long)buf + (i << IO_TLB_SHIFT),
> +				p + (i << IO_TLB_SHIFT),
>  				get_order(slabs << IO_TLB_SHIFT),
>  				dma_bits, &xen_dma_seg[j].dma_addr);
>  		} while (rc && dma_bits++ < max_dma_bits);
> @@ -389,7 +391,6 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
>  	void *ret;
>  	int order = get_order(size);
>  	u64 dma_mask = DMA_BIT_MASK(32);
> -	unsigned long vstart;
>  	phys_addr_t phys;
>  	dma_addr_t dev_addr;
>  
> @@ -404,8 +405,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
>  	if (dma_alloc_from_coherent(hwdev, size, dma_handle, &ret))
>  		return ret;
>  
> -	vstart = __get_free_pages(flags, order);
> -	ret = (void *)vstart;
> +	ret = xen_alloc_coherent_pages(hwdev, size, dma_handle, flags, attrs);
>  
>  	if (!ret)
>  		return ret;
> @@ -413,16 +413,20 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
>  	if (hwdev && hwdev->coherent_dma_mask)
>  		dma_mask = dma_alloc_coherent_mask(hwdev, flags);
>  
> -	phys = virt_to_phys(ret);
> +	/* At this point dma_handle is the physical address, next we are
> +	 * going to set it to the machine address.
> +	 * Do not use virt_to_phys(ret) because on ARM it doesn't correspond
> +	 * to *dma_handle. */
> +	phys = *dma_handle;
>  	dev_addr = xen_phys_to_bus(phys);
>  	if (!xen_feature(XENFEAT_auto_translated_physmap) &&
>  	    ((dev_addr + size - 1 <= dma_mask)) &&
>  	    !range_straddles_page_boundary(phys, size))
>  		*dma_handle = dev_addr;
>  	else {
> -		if (xen_create_contiguous_region(vstart, order,
> +		if (xen_create_contiguous_region(phys, order,
>  						 fls64(dma_mask), dma_handle) != 0) {
> -			free_pages(vstart, order);
> +			xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs);
>  			return NULL;
>  		}
>  	}
> @@ -445,14 +449,16 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
>  	if (hwdev && hwdev->coherent_dma_mask)
>  		dma_mask = hwdev->coherent_dma_mask;
>  
> -	phys = virt_to_phys(vaddr);
> +	/* do not use virt_to_phys because on ARM it doesn't return you the
> +	 * physical address */
> +	phys = xen_bus_to_phys(dev_addr);
>  
>  	if (xen_feature(XENFEAT_auto_translated_physmap) ||
>  		(((dev_addr + size - 1 > dma_mask)) ||
>  		 range_straddles_page_boundary(phys, size)))
>  		xen_destroy_contiguous_region((unsigned long)vaddr, order);
>  
> -	free_pages((unsigned long)vaddr, order);
> +	xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
>  }
>  EXPORT_SYMBOL_GPL(xen_swiotlb_free_coherent);
>  
> diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
> index 9ef704d..fb2ea8f 100644
> --- a/include/xen/xen-ops.h
> +++ b/include/xen/xen-ops.h
> @@ -19,11 +19,11 @@ void xen_arch_resume(void);
>  int xen_setup_shutdown_event(void);
>  
>  extern unsigned long *xen_contiguous_bitmap;
> -int xen_create_contiguous_region(unsigned long vstart, unsigned int order,
> +int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
>  				unsigned int address_bits,
>  				dma_addr_t *dma_handle);
>  
> -void xen_destroy_contiguous_region(unsigned long vstart, unsigned int order);
> +void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order);
>  
>  struct vm_area_struct;
>  int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
> -- 
> 1.7.2.5
> 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/