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Commit 499a5f1e authored by Jan Beulich's avatar Jan Beulich Committed by Ingo Molnar
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x86: Lift restriction on the location of FIX_BTMAP_* 



The early ioremap fixmap entries cover half (or for 32-bit
non-PAE, a quarter) of a page table, yet they got
uncondtitionally aligned so far to a 256-entry boundary. This is
not necessary if the range of page table entries anyway falls
into a single page table.

This buys back, for (theoretically) 50% of all configurations
(25% of all non-PAE ones), at least some of the lowmem
necessarily lost with commit e621bd18.

Signed-off-by: default avatarJan Beulich <jbeulich@novell.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <4B2BB66F0200007800026AD6@vpn.id2.novell.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 39d997b5

arch/x86/include/asm/fixmap.h

+11 −5
Original line number Diff line number Diff line
@@ -118,14 +118,20 @@ enum fixed_addresses { 
	 * 256 temporary boot-time mappings, used by early_ioremap(),

	 * before ioremap() is functional.

	 *

	 * We round it up to the next 256 pages boundary so that we

	 * can have a single pgd entry and a single pte table:

	 * If necessary we round it up to the next 256 pages boundary so

	 * that we can have a single pgd entry and a single pte table:

	 */

#define NR_FIX_BTMAPS		64

#define FIX_BTMAPS_SLOTS	4

	FIX_BTMAP_END = __end_of_permanent_fixed_addresses + 256 -

			(__end_of_permanent_fixed_addresses & 255),

	FIX_BTMAP_BEGIN = FIX_BTMAP_END + NR_FIX_BTMAPS*FIX_BTMAPS_SLOTS - 1,

#define TOTAL_FIX_BTMAPS	(NR_FIX_BTMAPS * FIX_BTMAPS_SLOTS)

	FIX_BTMAP_END =

	 (__end_of_permanent_fixed_addresses ^

	  (__end_of_permanent_fixed_addresses + TOTAL_FIX_BTMAPS - 1)) &

	 -PTRS_PER_PTE

	 ? __end_of_permanent_fixed_addresses + TOTAL_FIX_BTMAPS -

	   (__end_of_permanent_fixed_addresses & (TOTAL_FIX_BTMAPS - 1))

	 : __end_of_permanent_fixed_addresses,

	FIX_BTMAP_BEGIN = FIX_BTMAP_END + TOTAL_FIX_BTMAPS - 1,

#ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT

	FIX_OHCI1394_BASE,

#endif

arch/x86/mm/ioremap.c

+4 −0
Original line number Diff line number Diff line
@@ -422,6 +422,10 @@ void __init early_ioremap_init(void) 
	 * The boot-ioremap range spans multiple pmds, for which

	 * we are not prepared:

	 */

#define __FIXADDR_TOP (-PAGE_SIZE)

	BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)

		     != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));

#undef __FIXADDR_TOP

	if (pmd != early_ioremap_pmd(fix_to_virt(FIX_BTMAP_END))) {

		WARN_ON(1);

		printk(KERN_WARNING "pmd %p != %p\n",