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Subject: Re: [PATCH v3 09/11] swiotlb-xen: introduce phys_to_dma/dma_to_phys
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To:     Stefano Stabellini <sstabellini@kernel.org>,
        boris.ostrovsky@oracle.com, konrad.wilk@oracle.com
Cc:     xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
        hch@infradead.org,
        Stefano Stabellini <stefano.stabellini@xilinx.com>
References: <alpine.DEB.2.21.2007101521290.4124@sstabellini-ThinkPad-T480s>
 <20200710223427.6897-9-sstabellini@kernel.org>
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Date:   Tue, 4 Aug 2020 07:34:28 +0200
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On 11.07.20 00:34, Stefano Stabellini wrote:
> From: Stefano Stabellini <stefano.stabellini@xilinx.com>
> 
> With some devices physical addresses are different than dma addresses.
> To be able to deal with these cases, we need to call phys_to_dma on
> physical addresses (including machine addresses in Xen terminology)
> before returning them from xen_swiotlb_alloc_coherent and
> xen_swiotlb_map_page.
> 
> We also need to convert dma addresses back to physical addresses using
> dma_to_phys in xen_swiotlb_free_coherent and xen_swiotlb_unmap_page if
> we want to do any operations on them.
> 
> Call dma_to_phys in is_xen_swiotlb_buffer.
> Introduce xen_phys_to_dma and call phys_to_dma in its implementation.
> Introduce xen_dma_to_phys and call dma_to_phys in its implementation.
> Call xen_phys_to_dma/xen_dma_to_phys instead of
> xen_phys_to_bus/xen_bus_to_phys through swiotlb-xen.c.
> 
> 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@xilinx.com>
> Tested-by: Corey Minyard <cminyard@mvista.com>
> Tested-by: Roman Shaposhnik <roman@zededa.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen