[PATCH] Proper fix for highmem kmap_atomic functions for VMI for 2.6.21

Since lazy MMU batching mode still allows interrupts to enter, it is
possible for interrupt handlers to try to use kmap_atomic, which fails when
lazy mode is active, since the PTE update to highmem will be delayed.  The
best workaround is to issue an explicit flush in kmap_atomic_functions
case; this is the only way nested PTE updates can happen in the interrupt
handler.

Thanks to Jeremy Fitzhardinge for noting the bug and suggestions on a fix.

This patch gets reverted again when we start 2.6.22 and the bug gets fixed
differently.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Cc: Andi Kleen <ak@muc.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 00c23433b39f..6d7e279b1490 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -180,6 +180,7 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
 #ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
 #define arch_enter_lazy_mmu_mode()      do {} while (0)
 #define arch_leave_lazy_mmu_mode()      do {} while (0)
+#define arch_flush_lazy_mmu_mode()      do {} while (0)
 #endif
 
 /*
@@ -193,6 +194,7 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
 #ifndef __HAVE_ARCH_ENTER_LAZY_CPU_MODE
 #define arch_enter_lazy_cpu_mode()      do {} while (0)
 #define arch_leave_lazy_cpu_mode()      do {} while (0)
+#define arch_flush_lazy_cpu_mode()      do {} while (0)
 #endif
 
 /*