powerpc/32s: Fix boot failure with DEBUG_PAGEALLOC without KASAN.

When KASAN is selected, the definitive hash table has to be
set up later, but there is already an early temporary one.

When KASAN is not selected, there is no early hash table,
so the setup of the definitive hash table cannot be delayed.

Fixes: 72f208c6 ("powerpc/32s: move hash code patching out of MMU_init_hw()")
Cc: stable@vger.kernel.org # v5.2+
Reported-by: Jonathan Neuschafer <j.neuschaefer@gmx.net>
Tested-by: Jonathan Neuschafer <j.neuschaefer@gmx.net>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b7860c5e1e784d6b96ba67edf47dd6cbc2e78ab6.1565776892.git.christophe.leroy@c-s.fr

arch/powerpc/kernel/head_32.S

@@ -897,9 +897,11 @@ start_here:
 	bl	machine_init
 	bl	__save_cpu_setup
 	bl	MMU_init
+#ifdef CONFIG_KASAN
 BEGIN_MMU_FTR_SECTION
 	bl	MMU_init_hw_patch
 END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
+#endif
 
 /*
  * Go back to running unmapped so we can load up new values

arch/powerpc/mm/book3s32/mmu.c

@@ -358,6 +358,15 @@ void __init MMU_init_hw(void)
 	hash_mb2 = hash_mb = 32 - LG_HPTEG_SIZE - lg_n_hpteg;
 	if (lg_n_hpteg > 16)
 		hash_mb2 = 16 - LG_HPTEG_SIZE;
+
+	/*
+	 * When KASAN is selected, there is already an early temporary hash
+	 * table and the switch to the final hash table is done later.
+	 */
+	if (IS_ENABLED(CONFIG_KASAN))
+		return;
+
+	MMU_init_hw_patch();
 }
 
 void __init MMU_init_hw_patch(void)