powerpc: Pull out ksp_vsid logic into a helper

The previous patch left a bit of a wart in copy_process(). Clean it up a
bit by moving the logic out into a helper.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/process.c

@@ -1095,6 +1095,23 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 	return 0;
 }
 
+static void setup_ksp_vsid(struct task_struct *p, unsigned long sp)
+{
+#ifdef CONFIG_PPC_STD_MMU_64
+	unsigned long sp_vsid;
+	unsigned long llp = mmu_psize_defs[mmu_linear_psize].sllp;
+
+	if (mmu_has_feature(MMU_FTR_1T_SEGMENT))
+		sp_vsid = get_kernel_vsid(sp, MMU_SEGSIZE_1T)
+			<< SLB_VSID_SHIFT_1T;
+	else
+		sp_vsid = get_kernel_vsid(sp, MMU_SEGSIZE_256M)
+			<< SLB_VSID_SHIFT;
+	sp_vsid |= SLB_VSID_KERNEL | llp;
+	p->thread.ksp_vsid = sp_vsid;
+#endif
+}
+
 /*
  * Copy a thread..
  */
@@ -1174,21 +1191,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 	p->thread.vr_save_area = NULL;
 #endif
 
-#ifdef CONFIG_PPC_STD_MMU_64
-	{
-		unsigned long sp_vsid;
-		unsigned long llp = mmu_psize_defs[mmu_linear_psize].sllp;
+	setup_ksp_vsid(p, sp);
 
-		if (mmu_has_feature(MMU_FTR_1T_SEGMENT))
-			sp_vsid = get_kernel_vsid(sp, MMU_SEGSIZE_1T)
-				<< SLB_VSID_SHIFT_1T;
-		else
-			sp_vsid = get_kernel_vsid(sp, MMU_SEGSIZE_256M)
-				<< SLB_VSID_SHIFT;
-		sp_vsid |= SLB_VSID_KERNEL | llp;
-		p->thread.ksp_vsid = sp_vsid;
-	}
-#endif /* CONFIG_PPC_STD_MMU_64 */
 #ifdef CONFIG_PPC64 
 	if (cpu_has_feature(CPU_FTR_DSCR)) {
 		p->thread.dscr_inherit = current->thread.dscr_inherit;