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SubjectRe: [PATCH 10/28] i386: map enough initial memory to create lowmem mappings
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 <>
> Acked-by: "H. Peter Anvin" <>
> Cc: Andi Kleen <>
> Cc: Zachary Amsden <>
> Cc: Chris Wright <>
> Cc: "Eric W. Biederman" <>
> Cc: Linus Torvalds <>,

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