Re: i386 PAE support (Patches)

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

On 22.12.09 00:19, Jeremy Morse wrote:
> On 21/12/2009 21:21, Joerg Sonnenberger wrote:
>> On Mon, Dec 21, 2009 at 10:17:12PM +0100, Jean-Yves Migeon wrote:
>>> BTW, given that all mainstream x86 CPUs support PAE today, shouldn't
>>> PAE support be made more dynamic, by checking if feature is present
>>> (through CPUID for example), and adapt accordingly?
>>
>> That would mean switching the pmap at run time or using a more dynamic
>> pmap, both could cost performance. Using PAE really only makes sense if
>> high memory is present or NX on AMD cpus is desired.
> 
> In addition paddr_t's would be needlessly large for systems without PAE.
> As far as I know, no operating system currently supports both modes in
> one kernel.

Solaris is able to switch between 32bit and 32bit PAE at runtime.

Christoph