patch-2.3.11 linux/include/asm-i386/mmu_context.h

• Lines: 31
• Date: Mon Jul 19 16:18:57 1999
• Orig file: v2.3.10/linux/include/asm-i386/mmu_context.h
• Orig date: Tue May 5 21:33:33 1998

diff -u --recursive --new-file v2.3.10/linux/include/asm-i386/mmu_context.h linux/include/asm-i386/mmu_context.h
@@ -1,13 +1,27 @@
 #ifndef __I386_MMU_CONTEXT_H
 #define __I386_MMU_CONTEXT_H
 
+#include <asm/desc.h>
+
 /*
- * get a new mmu context.. x86's don't know about contexts.
+ * get a new mmu context.. x86's don't know much about contexts,
+ * but we have to reload the new LDT in exec().
+ *
+ * We implement lazy MMU context-switching on x86 to optimize context
+ * switches done to/from kernel threads. Kernel threads 'inherit' the
+ * previous MM, so Linux doesnt have to flush the TLB. In most cases
+ * we switch back to the same process so we preserve the TLB cache.
+ * This all means that kernel threads have about as much overhead as
+ * a function call ...
  */
-#define get_mmu_context(x) do { } while (0)
+#define get_mmu_context(next) do { } while (0)
+#define set_mmu_context(prev,next) do { next->thread.cr3 = prev->thread.cr3; } while(0)
 
 #define init_new_context(mm)	do { } while(0)
+/*
+ * possibly do the LDT unload here?
+ */
 #define destroy_context(mm)	do { } while(0)
-#define activate_context(tsk)	do { } while(0)
+#define activate_context(x)	load_LDT((x)->mm)
 
 #endif