Re: [Xen-devel] [PATCH v1 00/47] mtrr/x86/drivers: bury MTRR

[Andy Lutomirski <luto@xxxxxxxxxxxxxx>]

On Fri, Mar 20, 2015 at 4:17 PM, Luis R. Rodriguez
<mcgrof@xxxxxxxxxxxxxxxx> wrote:
> From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx>
>
> When a system has PAT support enabled you don't need to be
> using MTRRs. Andy had added arch_phys_wc_add() long ago to
> help with this but not all drivers were converted over. We
> have to take care to only convert drivers where we know that
> the proper ioremap_wc() API has been used. Doing this requires
> a bit of work on verifying the driver split out the ioremap'd
> areas -- and if not doing that ourselves. Verifying a driver
> uses the same areas can be hard but with a bit of love Coccinelle
> can help with that.
>
> We're motivated to change drivers for a few reasons:
>
> 1) Take advantage of PAT when available
>
> 2) Help with the goal of eventually using _PAGE_CACHE_UC over
>    _PAGE_CACHE_UC_MINUS on x86 on ioremap_nocache() (de33c442e)

Nice!

--Andy

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