Re: [Xen-devel] early_cpu_init() and identify_cpu()

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> Keir Fraser <keir@xxxxxxxxxxxxx> 17.07.07 09:55 >>>
>On 16/7/07 10:23, "Alan Cox" <alan@xxxxxxxxxxxxxxxxxxx> wrote:
>
>>> significant (though I assume WC would at best help a little, I'm considering
>>> other approaches, too): Scrolling a 1280x1024x16 screen takes, on the test
>>> system I'm primarily trying this out on, on the order of a second. This is
>> 
>> A lot of work on this has been done in X by the X and Gnome developers
>> including producing some routines which use the largest possible aligned
>> loads to reduce the big cost (which is PCI reads). Having a write
>> combining video memory can help (but some cards also put stuff like
>> command queues there which X cannot WC).
>
>Does this mean that defaulting to setting up WC on a power-of-two-sized
>region starting at the framebuffer address is not really safe on a fair
>number of systems?

So I suppose, also based on the fact that Linux is defensive here too in
defaulting to not touching the MTRRs at all. I implemented this in a similar
fashion for Xen now.

Jan


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