powerpc/mm: Split mmu_context handling

This splits the mmu_context handling between 32-bit hash based
processors, 64-bit hash based processors and everybody else.  This is
preliminary work for adding SMP support for BookE processors.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/asm-offsets.c

@@ -60,6 +60,7 @@ int main(void)
 {
 	DEFINE(THREAD, offsetof(struct task_struct, thread));
 	DEFINE(MM, offsetof(struct task_struct, mm));
+	DEFINE(MMCONTEXTID, offsetof(struct mm_struct, context.id));
 #ifdef CONFIG_PPC64
 	DEFINE(AUDITCONTEXT, offsetof(struct task_struct, audit_context));
 #else

arch/powerpc/kernel/head_32.S

@@ -31,6 +31,7 @@
 #include <asm/ppc_asm.h>
 #include <asm/asm-offsets.h>
 #include <asm/ptrace.h>
+#include <asm/bug.h>
 
 /* 601 only have IBAT; cr0.eq is set on 601 when using this macro */
 #define LOAD_BAT(n, reg, RA, RB)	\
@@ -1070,9 +1071,14 @@ start_here:
 	RFI
 
 /*
+ * void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next);
+ *
  * Set up the segment registers for a new context.
  */
-_ENTRY(set_context)
+_ENTRY(switch_mmu_context)
+	lwz	r3,MMCONTEXTID(r4)
+	cmpwi	cr0,r3,0
+	blt-	4f
 	mulli	r3,r3,897	/* multiply context by skew factor */
 	rlwinm	r3,r3,4,8,27	/* VSID = (context & 0xfffff) << 4 */
 	addis	r3,r3,0x6000	/* Set Ks, Ku bits */
@@ -1083,6 +1089,7 @@ _ENTRY(set_context)
 	/* Context switch the PTE pointer for the Abatron BDI2000.
 	 * The PGDIR is passed as second argument.
 	 */
+	lwz	r4,MM_PGD(r4)
 	lis	r5, KERNELBASE@h
 	lwz	r5, 0xf0(r5)
 	stw	r4, 0x4(r5)
@@ -1098,6 +1105,9 @@ _ENTRY(set_context)
 	sync
 	isync
 	blr
+4:	trap
+	EMIT_BUG_ENTRY 4b,__FILE__,__LINE__,0
+	blr
 
 /*
  * An undocumented "feature" of 604e requires that the v bit

arch/powerpc/kernel/ppc_ksyms.c

@@ -174,8 +174,7 @@ EXPORT_SYMBOL(cacheable_memcpy);
 #endif
 
 #ifdef CONFIG_PPC32
-EXPORT_SYMBOL(next_mmu_context);
-EXPORT_SYMBOL(set_context);
+EXPORT_SYMBOL(switch_mmu_context);
 #endif
 
 #ifdef CONFIG_PPC_STD_MMU_32

arch/powerpc/kernel/swsusp.c

@@ -34,6 +34,6 @@ void save_processor_state(void)
 void restore_processor_state(void)
 {
 #ifdef CONFIG_PPC32
-	set_context(current->active_mm->context.id, current->active_mm->pgd);
+	switch_mmu_context(NULL, current->active_mm);
 #endif
 }