linux-kernel - Re: [PATCH RFC 5/6] arm64/xen: implement xen

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Date:	Fri, 31 May 2013 16:56:13 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Will Deacon <Will.Deacon@....com>,
	"Ian.Campbell@...rix.com" <Ian.Campbell@...rix.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>
Subject: Re: [PATCH RFC 5/6] arm64/xen: implement xen_remap on arm64

On Fri, May 31, 2013 at 04:23:20PM +0100, Stefano Stabellini wrote:
> On Fri, 31 May 2013, Stefano Stabellini wrote:
> > On Fri, 31 May 2013, Catalin Marinas wrote:
> > > On Fri, May 31, 2013 at 02:21:16PM +0100, Stefano Stabellini wrote:
> > > > On Fri, 31 May 2013, Catalin Marinas wrote:
> > > > > On Thu, May 30, 2013 at 05:18:32PM +0100, Stefano Stabellini wrote:
> > > > > > --- a/arch/arm/include/asm/xen/page.h
> > > > > > +++ b/arch/arm/include/asm/xen/page.h
> > > > > > @@ -90,6 +90,10 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
> > > > > >  	return __set_phys_to_machine(pfn, mfn);
> > > > > >  }
> > > > > >  
> > > > > > +#ifdef CONFIG_ARM64
> > > > > > +#define xen_remap(cookie, size) __ioremap((cookie), (size), __pgprot(PROT_NORMAL))
> > > > > > +#else
> > > > > >  #define xen_remap(cookie, size) __arm_ioremap((cookie), (size), MT_MEMORY);
> > > > > > +#endif
> > > > > 
> > > > > Now I saw the ARM-specific part. Can you not use something like
> > > > > ioremap_cached() which would give normal cacheable memory (at least on
> > > > > ARMv7).
> > > > 
> > > > No, I cannot because ioremap_cached uses MT_DEVICE_CACHED, while this
> > > > needs to be MT_MEMORY. It is used for normal memory pages, not device
> > > > memory.
> > > 
> > > MT_DEVICE_CACHED is Normal memory for ARMv7.
> > 
> > I didn't realize that MT_DEVICE_CACHED and MT_MEMORY end up having the
> > same AttrIndx encoding!
> > In that case yes, I should be able to use it.
> > I take that I should just implement ioremap_cached on arm64 as well?
> > 
> 
> Should just use MT_MEMORY and call it PROT_NORMAL?
> 
> #define PROT_NORMAL     (PROT_DEFAULT | PTE_ATTRINDX(MT_NORMAL))
> #define ioremap_cached(addr, size)     __ioremap((addr), (size), __pgprot(PROT_NORMAL))

Looks fine.

-- 
Catalin
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