linux-kernel - Re: [PATCH v8 10/13] xen/arm/arm64: introduce xen_arch_need

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Date:	Tue, 11 Nov 2014 11:52:25 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
	"Ian.Campbell@...rix.com" <Ian.Campbell@...rix.com>,
	"david.vrabel@...rix.com" <david.vrabel@...rix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v8 10/13] xen/arm/arm64: introduce
 xen_arch_need_swiotlb

On Mon, 10 Nov 2014, Catalin Marinas wrote:
> On Mon, Nov 10, 2014 at 04:14:02PM +0000, Stefano Stabellini wrote:
> > --- a/arch/arm/include/asm/xen/page.h
> > +++ b/arch/arm/include/asm/xen/page.h
> > @@ -107,4 +107,8 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
> >  #define xen_remap(cookie, size) ioremap_cache((cookie), (size))
> >  #define xen_unmap(cookie) iounmap((cookie))
> >  
> > +bool xen_arch_need_swiotlb(struct device *dev,
> > +			   unsigned long pfn,
> > +			   unsigned long mfn);
> > +
> >  #endif /* _ASM_ARM_XEN_PAGE_H */
> > diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
> > index 0e96023..1b087cd 100644
> > --- a/arch/arm/xen/mm.c
> > +++ b/arch/arm/xen/mm.c
> > @@ -102,6 +102,13 @@ void __xen_dma_sync_single_for_device(struct device *hwdev,
> >  	__xen_dma_page_cpu_to_dev(hwdev, handle, size, dir);
> >  }
> >  
> > +bool xen_arch_need_swiotlb(struct device *dev,
> > +			   unsigned long pfn,
> > +			   unsigned long mfn)
> > +{
> > +	return ((pfn != mfn) && !is_device_dma_coherent(dev));
> > +}
> 
> Why not a static inline? It doesn't look like a big function.

Because the next patch is going to make this change:

-   return ((pfn != mfn) && !is_device_dma_coherent(dev));
+   return (!hypercall_cflush && (pfn != mfn) && !is_device_dma_coherent(dev));

and I think it makes sense to keep hypercall_cflush as a static variable
within arch/arm/xen/mm.c (avoid exporting it in page.h).
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