__va() vs phys_to_virt()

__va() vs phys_to_virt()

[Hollis Blanchard]

Can someone explain where it's appropriate to use __va() and where 
phys_to_virt() should be used instead? Or are they truly synonymous, and we 
should phase out one or the other?

-- 
Hollis Blanchard
IBM Linux Technology Center


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Re: __va() vs phys_to_virt()

[Xin Zhao]

I thought they are the same. phys_to_virt() essentially calls __va().

Xin


On Fri, 18 Mar 2005, Hollis Blanchard wrote:

> Can someone explain where it's appropriate to use __va() and where
> phys_to_virt() should be used instead? Or are they truly synonymous, and we
> should phase out one or the other?
>
> --
> Hollis Blanchard
> IBM Linux Technology Center
>
>
> -------------------------------------------------------
> SF email is sponsored by - The IT Product Guide
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> _______________________________________________
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> Xen-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/xen-devel
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Re: __va() vs phys_to_virt()

[Hollis Blanchard]

On Friday 18 March 2005 12:45, Xin Zhao wrote:
> I thought they are the same. phys_to_virt() essentially calls __va().

They are implemented the same on x86, but that does not imply they mean the 
same thing.

> On Fri, 18 Mar 2005, Hollis Blanchard wrote:
> > Can someone explain where it's appropriate to use __va() and where
> > phys_to_virt() should be used instead? Or are they truly synonymous, and
> > we should phase out one or the other?
> >
> > --
> > Hollis Blanchard
> > IBM Linux Technology Center
> >
> >
> > -------------------------------------------------------
> > SF email is sponsored by - The IT Product Guide
> > Read honest & candid reviews on hundreds of IT Products from real users.
> > Discover which products truly live up to the hype. Start reading now.
> > http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/xen-devel

-- 
Hollis Blanchard
IBM Linux Technology Center


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Re: __va() vs phys_to_virt()

[Jesse Barnes]

On Friday, March 18, 2005 10:46 am, Hollis Blanchard wrote:
> On Friday 18 March 2005 12:45, Xin Zhao wrote:
> > I thought they are the same. phys_to_virt() essentially calls __va().
>
> They are implemented the same on x86, but that does not imply they mean the
> same thing.

A quick grep shows that most platforms implement __va and phys_to_virt the 
same way, as addr + PAGE_OFFSET.  But alpha seems to do phys_to_virt a little 
differently.  There may be others though, it was only a quick scan.

Jesse


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Re: __va() vs phys_to_virt()

[Hollis Blanchard]

On Friday 18 March 2005 12:59, Jesse Barnes wrote:
> On Friday, March 18, 2005 10:46 am, Hollis Blanchard wrote:
> > On Friday 18 March 2005 12:45, Xin Zhao wrote:
> > > I thought they are the same. phys_to_virt() essentially calls __va().
> >
> > They are implemented the same on x86, but that does not imply they mean
> > the same thing.
>
> A quick grep shows that most platforms implement __va and phys_to_virt the
> same way, as addr + PAGE_OFFSET.  But alpha seems to do phys_to_virt a
> little differently.  There may be others though, it was only a quick scan.

I should clarify that I'm not talking about Linux, but rather the Xen core. 
Linux's use is obviously related, as Xen was a copy-and-paste job, but I'm 
asking specifically how/if the meanings of these functions differ in Xen.

-- 
Hollis Blanchard
IBM Linux Technology Center


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Re: __va() vs phys_to_virt()

[Dave Hansen]

On Fri, 2005-03-18 at 12:32 -0600, Hollis Blanchard wrote:
> Can someone explain where it's appropriate to use __va() and where 
> phys_to_virt() should be used instead? Or are they truly synonymous, and we 
> should phase out one or the other?

One minor thing on some Linux arches is that virt_to_phys() is volatile,
__pa() is just a macro, so they have different optimization rules.

-- Dave



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