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Date: Tue, 11 Nov 2014 11:07:32 +0000
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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To: Catalin Marinas <catalin.marinas@arm.com>
CC: Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
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	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v8 03/13] xen/arm: if(pfn_valid(pfn)) call native
 dma_ops
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On Mon, 10 Nov 2014, Catalin Marinas wrote:
> On Mon, Nov 10, 2014 at 04:13:55PM +0000, Stefano Stabellini wrote:
> >  void xen_dma_unmap_page(struct device *hwdev, dma_addr_t handle,
> >  		size_t size, enum dma_data_direction dir,
> > -		struct dma_attrs *attrs);
> > +		struct dma_attrs *attrs)
> > +{
> > +	unsigned long pfn = PFN_DOWN(handle);
> > +	/* Dom0 is mapped 1:1, so calling pfn_valid on a foreign mfn will
> > +	 * always return false. If the page is local we can safely call the
> > +	 * native dma_ops function, otherwise we call the xen specific
> > +	 * function. */
> > +	if (pfn_valid(pfn)) {
> > +		if (__generic_dma_ops(hwdev)->unmap_page)
> > +			__generic_dma_ops(hwdev)->unmap_page(hwdev, handle, size, dir, attrs);
> 
> Similarly here, do we need the unmap_page check? dma_map_page() does not
> do it.

I think we do not need the map_page check, because that's always
implemented, but we need the unmap_page check. In fact
arm_coherent_dma_ops doesn't have unmap_page for example.