Re: [Xen-devel] CONFIG_XEN_COMPAT_030002 broken?

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 13/11/06 16:47, "Gerd Hoffmann" <kraxel@xxxxxxx> wrote:

>> To fix this we'd need to make all the KERNPG_XXX macros into variables and
>> poke in PAGE_USER if running on an older version of Xen.
> 
> As xen must be able to deal with PAGE_USER being set anyway (to deal
> with old guests) I'd simply make that a compile time option depending on
> CONFIG_XEN_COMPAT_030002, so we can avoid the extra cost of checking
> some variable at runtime ...
> 
> What was the reason for that change btw?  Just make the differences
> between native and paravirtualized smaller?

Yes, and to allow fewer TLB entries to be flushed when switching between
guest kernel and guest user. That optimisation is foiled if PAGE_USER is set
everywhere.

 -- Keir



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