powerpc/mm/hash: Store addr_limit in PACA

We optmize the slice page size array copy to paca by copying only the
range based on addr_limit. This will require us to not look at page size
array beyond addr_limit in PACA on slb fault. To enable that copy task
size to paca which will be used during slb fault.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
[mpe: Rename from task_size to addr_limit, consolidate #ifdefs]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/paca.h

@@ -139,6 +139,7 @@ struct paca_struct {
 #ifdef CONFIG_PPC_MM_SLICES
 	u64 mm_ctx_low_slices_psize;
 	unsigned char mm_ctx_high_slices_psize[SLICE_ARRAY_SIZE];
+	unsigned long addr_limit;
 #else
 	u16 mm_ctx_user_psize;
 	u16 mm_ctx_sllp;

arch/powerpc/kernel/asm-offsets.c

@@ -185,6 +185,7 @@ int main(void)
 #ifdef CONFIG_PPC_MM_SLICES
 	OFFSET(PACALOWSLICESPSIZE, paca_struct, mm_ctx_low_slices_psize);
 	OFFSET(PACAHIGHSLICEPSIZE, paca_struct, mm_ctx_high_slices_psize);
+	DEFINE(PACA_ADDR_LIMIT, offsetof(struct paca_struct, addr_limit));
 	DEFINE(MMUPSIZEDEFSIZE, sizeof(struct mmu_psize_def));
 #endif /* CONFIG_PPC_MM_SLICES */
 #endif

arch/powerpc/kernel/paca.c

@@ -254,6 +254,7 @@ void copy_mm_to_paca(struct mm_struct *mm)
 	get_paca()->mm_ctx_id = context->id;
 #ifdef CONFIG_PPC_MM_SLICES
 	VM_BUG_ON(!mm->context.addr_limit);
+	get_paca()->addr_limit = mm->context.addr_limit;
 	get_paca()->mm_ctx_low_slices_psize = context->low_slices_psize;
 	memcpy(&get_paca()->mm_ctx_high_slices_psize,
 	       &context->high_slices_psize, TASK_SLICE_ARRAY_SZ(mm));

arch/powerpc/mm/slb_low.S

@@ -149,7 +149,13 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_1T_SEGMENT)
 	 * For userspace addresses, make sure this is region 0.
 	 */
 	cmpdi	r9, 0
-	bne	8f
+	bne-	8f
+        /*
+         * user space make sure we are within the allowed limit
+	 */
+	ld	r11,PACA_ADDR_LIMIT(r13)
+	cmpld	r3,r11
+	bge-	8f
 
 	/* when using slices, we extract the psize off the slice bitmaps
 	 * and then we need to get the sllp encoding off the mmu_psize_defs