linux-kernel - Re: [PATCH 08/10] swiotlb-xen: introduce phys_to_dma/dma_to

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Date:   Thu, 21 May 2020 18:59:28 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Stefano Stabellini <sstabellini@...nel.org>, jgross@...e.com,
        konrad.wilk@...cle.com
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        Stefano Stabellini <stefano.stabellini@...inx.com>
Subject: Re: [PATCH 08/10] swiotlb-xen: introduce phys_to_dma/dma_to_phys
 translations

On 5/20/20 7:45 PM, Stefano Stabellini wrote:
> From: Stefano Stabellini <stefano.stabellini@...inx.com>
>
> Call dma_to_phys in is_xen_swiotlb_buffer.
> Call phys_to_dma in xen_phys_to_bus.
> Call dma_to_phys in xen_bus_to_phys.
>
> Everything is taken care of by these changes except for
> xen_swiotlb_alloc_coherent and xen_swiotlb_free_coherent, which need a
> few explicit phys_to_dma/dma_to_phys calls.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...inx.com>
> ---
>  drivers/xen/swiotlb-xen.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index c50448fd9b75..d011c4c7aa72 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -64,14 +64,16 @@ static inline dma_addr_t xen_phys_to_bus(struct device *dev, phys_addr_t paddr)
>  
>  	dma |= paddr & ~XEN_PAGE_MASK;
>  
> -	return dma;
> +	return phys_to_dma(dev, dma);
>  }
>  
> -static inline phys_addr_t xen_bus_to_phys(struct device *dev, dma_addr_t baddr)
> +static inline phys_addr_t xen_bus_to_phys(struct device *dev,
> +					  dma_addr_t dma_addr)


Since now dma address != bus address this is no longer
xen_bus_to_phys(). (And I guess the same is rue for xen_phys_to_bus()).


>  {
> +	phys_addr_t baddr = dma_to_phys(dev, dma_addr);
>  	unsigned long xen_pfn = bfn_to_pfn(XEN_PFN_DOWN(baddr));
> -	dma_addr_t dma = (dma_addr_t)xen_pfn << XEN_PAGE_SHIFT;
> -	phys_addr_t paddr = dma;
> +	phys_addr_t paddr = (xen_pfn << XEN_PAGE_SHIFT) |
> +			    (baddr & ~XEN_PAGE_MASK);
>  
>  	paddr |= baddr & ~XEN_PAGE_MASK;


This line needs to go, no?


-boris