powerpc: Add function to copy mm_context_t to the paca

This adds a function to copy the mm->context to the paca.  This is
only a basic conversion for now but will be used more extensively in
the next patch.

This also adds #ifdef CONFIG_PPC_BOOK3S around this code since it's
not used elsewhere.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/paca.h

@@ -131,7 +131,9 @@ struct paca_struct {
 	struct tlb_core_data tcd;
 #endif /* CONFIG_PPC_BOOK3E */
 
+#ifdef CONFIG_PPC_BOOK3S
 	mm_context_t context;
+#endif
 
 	/*
 	 * then miscellaneous read-write fields
@@ -194,6 +196,15 @@ struct paca_struct {
 #endif
 };
 
+#ifdef CONFIG_PPC_BOOK3S
+static inline void copy_mm_to_paca(mm_context_t *context)
+{
+	get_paca()->context = *context;
+}
+#else
+static inline void copy_mm_to_paca(mm_context_t *context){}
+#endif
+
 extern struct paca_struct *paca;
 extern void initialise_paca(struct paca_struct *new_paca, int cpu);
 extern void setup_paca(struct paca_struct *new_paca);

arch/powerpc/kernel/asm-offsets.c

@@ -185,6 +185,7 @@ int main(void)
 	DEFINE(PACAKMSR, offsetof(struct paca_struct, kernel_msr));
 	DEFINE(PACASOFTIRQEN, offsetof(struct paca_struct, soft_enabled));
 	DEFINE(PACAIRQHAPPENED, offsetof(struct paca_struct, irq_happened));
+#ifdef CONFIG_PPC_BOOK3S
 	DEFINE(PACACONTEXTID, offsetof(struct paca_struct, context.id));
 #ifdef CONFIG_PPC_MM_SLICES
 	DEFINE(PACALOWSLICESPSIZE, offsetof(struct paca_struct,
@@ -193,6 +194,7 @@ int main(void)
 					    context.high_slices_psize));
 	DEFINE(MMUPSIZEDEFSIZE, sizeof(struct mmu_psize_def));
 #endif /* CONFIG_PPC_MM_SLICES */
+#endif
 
 #ifdef CONFIG_PPC_BOOK3E
 	DEFINE(PACAPGD, offsetof(struct paca_struct, pgd));

arch/powerpc/mm/hash_utils_64.c

@@ -882,7 +882,8 @@ void demote_segment_4k(struct mm_struct *mm, unsigned long addr)
 	slice_set_range_psize(mm, addr, 1, MMU_PAGE_4K);
 	copro_flush_all_slbs(mm);
 	if ((get_paca_psize(addr) != MMU_PAGE_4K) && (current->mm == mm)) {
-		get_paca()->context = mm->context;
+
+		copy_mm_to_paca(&mm->context);
 		slb_flush_and_rebolt();
 	}
 }
@@ -949,7 +950,7 @@ static void check_paca_psize(unsigned long ea, struct mm_struct *mm,
 {
 	if (user_region) {
 		if (psize != get_paca_psize(ea)) {
-			get_paca()->context = mm->context;
+			copy_mm_to_paca(&mm->context);
 			slb_flush_and_rebolt();
 		}
 	} else if (get_paca()->vmalloc_sllp !=

arch/powerpc/mm/slb.c

@@ -228,7 +228,7 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
 		asm volatile("slbie %0" : : "r" (slbie_data));
 
 	get_paca()->slb_cache_ptr = 0;
-	get_paca()->context = mm->context;
+	copy_mm_to_paca(&mm->context);
 
 	/*
 	 * preload some userspace segments into the SLB.

arch/powerpc/mm/slice.c

@@ -185,8 +185,7 @@ static void slice_flush_segments(void *parm)
 	if (mm != current->active_mm)
 		return;
 
-	/* update the paca copy of the context struct */
-	get_paca()->context = current->active_mm->context;
+	copy_mm_to_paca(&current->active_mm->context);
 
 	local_irq_save(flags);
 	slb_flush_and_rebolt();