Re: [PATCH 10/28] i386: map enough initial memory to create lowmemmappings

[Chuck Ebbert]

Jeremy Fitzhardinge wrote:
> head.S creates the very initial pagetable for the kernel.  This just
> maps enough space for the kernel itself, and an allocation bitmap.
> The amount of mapped memory is rounded up to 4Mbytes, and so this
> typically ends up mapping 8Mbytes of memory.
> 
> When booting, pagetable_init() needs to create mappings for all
> lowmem, and the pagetables for these mappings are allocated from the
> free pages around the kernel in low memory.  If the number of
> pagetable pages + kernel size exceeds head.S's initial mapping, it
> will end up faulting on an unmapped page.  This will only happen with
> specific combinations of kernel size and memory size.
> 
> This patch makes sure that head.S also maps enough space to fit the
> kernel pagetables as well as the kernel itself.  It ends up using an
> additional two pages of unreclaimable memory.
> 
> Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
> Acked-by: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Andi Kleen <ak@xxxxxxx>
> Cc: Zachary Amsden <zach@xxxxxxxxxx>
> Cc: Chris Wright <chrisw@xxxxxxxxxxxx>
> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>,

Is some version of this going in for 2.6.21, or is it not a real problem?
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