powerpc/8xx: Prepare handlers for _PAGE_HUGE for 512k pages.

Prepare ITLB handler to handle _PAGE_HUGE when CONFIG_HUGETLBFS
is enabled. This means that the L1 entry has to be kept in r11
until L2 entry is read, in order to insert _PAGE_HUGE into it.

Also move pgd_offset helpers before pte_update() as they
will be needed there in next patch.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/21fd1de8fba781bededa9474a5a9374aefb1f849.1589866984.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/nohash/32/pgtable.h

@@ -206,6 +206,12 @@ static inline void pmd_clear(pmd_t *pmdp)
 }
 
 
+/* to find an entry in a kernel page-table-directory */
+#define pgd_offset_k(address) pgd_offset(&init_mm, address)
+
+/* to find an entry in a page-table-directory */
+#define pgd_index(address)	 ((address) >> PGDIR_SHIFT)
+#define pgd_offset(mm, address)	 ((mm)->pgd + pgd_index(address))
 
 /*
  * PTE updates. This function is called whenever an existing
@@ -348,13 +354,6 @@ static inline int pte_young(pte_t pte)
 	pfn_to_page((__pa(pmd_val(pmd)) >> PAGE_SHIFT))
 #endif
 
-/* to find an entry in a kernel page-table-directory */
-#define pgd_offset_k(address) pgd_offset(&init_mm, address)
-
-/* to find an entry in a page-table-directory */
-#define pgd_index(address)	 ((address) >> PGDIR_SHIFT)
-#define pgd_offset(mm, address)	 ((mm)->pgd + pgd_index(address))
-
 /* Find an entry in the third-level page table.. */
 #define pte_index(address)		\
 	(((address) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))

arch/powerpc/kernel/head_8xx.S

@@ -196,7 +196,7 @@ SystemCall:
 
 InstructionTLBMiss:
 	mtspr	SPRN_SPRG_SCRATCH0, r10
-#if defined(ITLB_MISS_KERNEL) || defined(CONFIG_SWAP)
+#if defined(ITLB_MISS_KERNEL) || defined(CONFIG_SWAP) || defined(CONFIG_HUGETLBFS)
 	mtspr	SPRN_SPRG_SCRATCH1, r11
 #endif
 
@@ -235,16 +235,19 @@ InstructionTLBMiss:
 	rlwinm	r10, r10, 0, 20, 31
 	oris	r10, r10, (swapper_pg_dir - PAGE_OFFSET)@ha
 3:
+	mtcr	r11
 #endif
+#ifdef CONFIG_HUGETLBFS
+	lwz	r11, (swapper_pg_dir-PAGE_OFFSET)@l(r10)	/* Get level 1 entry */
+	mtspr	SPRN_MI_TWC, r11	/* Set segment attributes */
+	mtspr	SPRN_MD_TWC, r11
+#else
 	lwz	r10, (swapper_pg_dir-PAGE_OFFSET)@l(r10)	/* Get level 1 entry */
 	mtspr	SPRN_MI_TWC, r10	/* Set segment attributes */
-
 	mtspr	SPRN_MD_TWC, r10
+#endif
 	mfspr	r10, SPRN_MD_TWC
 	lwz	r10, 0(r10)	/* Get the pte */
-#ifdef ITLB_MISS_KERNEL
-	mtcr	r11
-#endif
 #ifdef CONFIG_SWAP
 	rlwinm	r11, r10, 32-5, _PAGE_PRESENT
 	and	r11, r11, r10
@@ -263,7 +266,7 @@ InstructionTLBMiss:
 
 	/* Restore registers */
 0:	mfspr	r10, SPRN_SPRG_SCRATCH0
-#if defined(ITLB_MISS_KERNEL) || defined(CONFIG_SWAP)
+#if defined(ITLB_MISS_KERNEL) || defined(CONFIG_SWAP) || defined(CONFIG_HUGETLBFS)
 	mfspr	r11, SPRN_SPRG_SCRATCH1
 #endif
 	rfi