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 e621bd18958ef5dbace3129ebe17a0a475e127d9.
Signed-off-by: Jan 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: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
index 14f9890..635f03b 100644
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -118,14 +118,20 @@
* 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
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index c246d25..03c75ff 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -422,6 +422,10 @@
* 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",