Re: [PATCH] x86: simplify HIGHMEM-related Kconfig entries

From: Jan Beulich
Date: Fri Jan 16 2009 - 06:56:42 EST


>>> "H. Peter Anvin" <hpa@xxxxxxxxx> 15.01.09 18:10 >>>
>Ingo Molnar wrote:
>>>>
>>>> No highmem - No highmem, no PAE
>>>> HIGHMEM4G - Highmem, no PAE
>>>> HIGHMEM64G - Highmem, PAE
>>>>
>>>> So X86_PAE and HIGHMEM4G is a bit of a contradiction. I haven't looked
>>>> at the logic in detail, or remember offhand if there have been any
>>>> weakening of the definitions above; e.g. someone could have implemented
>>>> a way to do PAE without highmem, to get access to the NX bits.
>>> Exactly - .23 made PAE an independently selectable option (in
>>> particular, the no-highmem+PAE combination is now valid), but I can't
>>> see why it added the !HIGHMEM4G dependency.
>>
>> There's no deep reason, it just has never really been tested that way. I
>> think we should try it.
>
>If so, what would be the difference between HIGHMEM4G and HIGHMEM64G in
>that case at all?

For example being able to select the DMADEVICES config option.

Jan

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