WIP: powerpc: Fix kfence for book3s64 radix mmu

The existing patch uses the DEBUG_PAGEALLOC logic to implement kfence's
mapping/unmapping callback. However DEBUG_PAGEALLOC is only available
for hash MMU on book3s64 systems, leading to a crash when running under
radix.

The ppc32 implementation calls generic page handling code that appears
to be ok to call for hash. If we let hash use this code we can pass the
kfence kunit test suite.

However we sometimes crash soon after (under qemu), so something is not
quite right.

Signed-off-by: Joel Stanley <joel@jms.id.au>

arch/powerpc/include/asm/kfence.h

@@ -15,18 +15,20 @@
 #define ARCH_FUNC_PREFIX "."
 #endif
 
+bool hash__kfence_protect_page(unsigned long addr, bool protect);
+
 static inline bool arch_kfence_init_pool(void)
 {
 	return true;
 }
 
-#ifdef CONFIG_PPC64
-bool kfence_protect_page(unsigned long addr, bool protect);
-#else
 static inline bool kfence_protect_page(unsigned long addr, bool protect)
 {
 	pte_t *kpte = virt_to_kpte(addr);
 
+	if (IS_ENABLED(CONFIG_BOOK3S_64) && !radix_enabled())
+		return hash__kfence_protect_page(addr, protect);
+
 	if (protect) {
 		pte_update(&init_mm, addr, kpte, _PAGE_PRESENT, 0, 0);
 		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
@@ -36,6 +38,5 @@ static inline bool kfence_protect_page(unsigned long addr, bool protect)
 
 	return true;
 }
-#endif
 
 #endif /* __ASM_POWERPC_KFENCE_H */

arch/powerpc/mm/book3s64/hash_utils.c

@@ -1983,7 +1983,7 @@ static void kernel_unmap_linear_page(unsigned long vaddr, unsigned long lmi)
 }
 
 #ifdef CONFIG_KFENCE
-bool kfence_protect_page(unsigned long addr, bool protect)
+bool hash__kfence_protect_page(unsigned long addr, bool protect)
 {
 	unsigned long lmi = __pa(addr) >> PAGE_SHIFT;