Revert "powerpc/32s: reorder Linux PTE bits to better match Hash PTE bits."

This reverts commit 697ece78.

The implementation of SWAP on powerpc requires page protection
bits to not be one of the least significant PTE bits.

Until the SWAP implementation is changed and this requirement voids,
we have to keep at least _PAGE_RW outside of the 3 last bits.

For now, revert to previous PTE bits order. A further rework
may come later.

Fixes: 697ece78 ("powerpc/32s: reorder Linux PTE bits to better match Hash PTE bits.")
Reported-by: Rui Salvaterra <rsalvaterra@gmail.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b34706f8de87f84d135abb5f3ede6b6f16fb1f41.1589969799.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/book3s/32/hash.h

@@ -17,9 +17,9 @@
  * updating the accessed and modified bits in the page table tree.
  */
 
-#define _PAGE_USER	0x001	/* usermode access allowed */
-#define _PAGE_RW	0x002	/* software: user write access allowed */
-#define _PAGE_PRESENT	0x004	/* software: pte contains a translation */
+#define _PAGE_PRESENT	0x001	/* software: pte contains a translation */
+#define _PAGE_HASHPTE	0x002	/* hash_page has made an HPTE for this pte */
+#define _PAGE_USER	0x004	/* usermode access allowed */
 #define _PAGE_GUARDED	0x008	/* G: prohibit speculative access */
 #define _PAGE_COHERENT	0x010	/* M: enforce memory coherence (SMP systems) */
 #define _PAGE_NO_CACHE	0x020	/* I: cache inhibit */
@@ -27,7 +27,7 @@
 #define _PAGE_DIRTY	0x080	/* C: page changed */
 #define _PAGE_ACCESSED	0x100	/* R: page referenced */
 #define _PAGE_EXEC	0x200	/* software: exec allowed */
-#define _PAGE_HASHPTE	0x400	/* hash_page has made an HPTE for this pte */
+#define _PAGE_RW	0x400	/* software: user write access allowed */
 #define _PAGE_SPECIAL	0x800	/* software: Special page */
 
 #ifdef CONFIG_PTE_64BIT

arch/powerpc/kernel/head_32.S

@@ -348,7 +348,7 @@ BEGIN_MMU_FTR_SECTION
 	andis.	r0, r5, (DSISR_BAD_FAULT_32S | DSISR_DABRMATCH)@h
 #endif
 	bne	handle_page_fault_tramp_2	/* if not, try to put a PTE */
-	rlwinm	r3, r5, 32 - 24, 30, 30		/* DSISR_STORE -> _PAGE_RW */
+	rlwinm	r3, r5, 32 - 15, 21, 21		/* DSISR_STORE -> _PAGE_RW */
 	bl	hash_page
 	b	handle_page_fault_tramp_1
 FTR_SECTION_ELSE
@@ -497,6 +497,7 @@ InstructionTLBMiss:
 	andc.	r1,r1,r0		/* check access & ~permission */
 	bne-	InstructionAddressInvalid /* return if access not permitted */
 	/* Convert linux-style PTE to low word of PPC-style PTE */
+	rlwimi	r0,r0,32-2,31,31	/* _PAGE_USER -> PP lsb */
 	ori	r1, r1, 0xe06		/* clear out reserved bits */
 	andc	r1, r0, r1		/* PP = user? 1 : 0 */
 BEGIN_FTR_SECTION
@@ -564,8 +565,9 @@ DataLoadTLBMiss:
 	 * we would need to update the pte atomically with lwarx/stwcx.
 	 */
 	/* Convert linux-style PTE to low word of PPC-style PTE */
-	rlwinm	r1,r0,0,30,30		/* _PAGE_RW -> PP msb */
-	rlwimi	r0,r0,1,30,30		/* _PAGE_USER -> PP msb */
+	rlwinm	r1,r0,32-9,30,30	/* _PAGE_RW -> PP msb */
+	rlwimi	r0,r0,32-1,30,30	/* _PAGE_USER -> PP msb */
+	rlwimi	r0,r0,32-1,31,31	/* _PAGE_USER -> PP lsb */
 	ori	r1,r1,0xe04		/* clear out reserved bits */
 	andc	r1,r0,r1		/* PP = user? rw? 1: 3: 0 */
 BEGIN_FTR_SECTION
@@ -643,6 +645,7 @@ DataStoreTLBMiss:
 	 * we would need to update the pte atomically with lwarx/stwcx.
 	 */
 	/* Convert linux-style PTE to low word of PPC-style PTE */
+	rlwimi	r0,r0,32-2,31,31	/* _PAGE_USER -> PP lsb */
 	li	r1,0xe06		/* clear out reserved bits & PP msb */
 	andc	r1,r0,r1		/* PP = user? 1: 0 */
 BEGIN_FTR_SECTION

arch/powerpc/mm/book3s32/hash_low.S

@@ -35,7 +35,7 @@ mmu_hash_lock:
 /*
  * Load a PTE into the hash table, if possible.
  * The address is in r4, and r3 contains an access flag:
- * _PAGE_RW (0x002) if a write.
+ * _PAGE_RW (0x400) if a write.
  * r9 contains the SRR1 value, from which we use the MSR_PR bit.
  * SPRG_THREAD contains the physical address of the current task's thread.
  *
@@ -69,7 +69,7 @@ _GLOBAL(hash_page)
 	blt+	112f			/* assume user more likely */
 	lis	r5, (swapper_pg_dir - PAGE_OFFSET)@ha	/* if kernel address, use */
 	addi	r5 ,r5 ,(swapper_pg_dir - PAGE_OFFSET)@l	/* kernel page table */
-	rlwimi	r3,r9,32-14,31,31	/* MSR_PR -> _PAGE_USER */
+	rlwimi	r3,r9,32-12,29,29	/* MSR_PR -> _PAGE_USER */
 112:
 #ifndef CONFIG_PTE_64BIT
 	rlwimi	r5,r4,12,20,29		/* insert top 10 bits of address */
@@ -94,7 +94,7 @@ _GLOBAL(hash_page)
 #else
 	rlwimi	r8,r4,23,20,28		/* compute pte address */
 #endif
-	rlwinm	r0,r3,6,24,24		/* _PAGE_RW access -> _PAGE_DIRTY */
+	rlwinm	r0,r3,32-3,24,24	/* _PAGE_RW access -> _PAGE_DIRTY */
 	ori	r0,r0,_PAGE_ACCESSED|_PAGE_HASHPTE
 
 	/*
@@ -310,9 +310,11 @@ Hash_msk = (((1 << Hash_bits) - 1) * 64)
 
 _GLOBAL(create_hpte)
 	/* Convert linux-style PTE (r5) to low word of PPC-style PTE (r8) */
+	rlwinm	r8,r5,32-9,30,30	/* _PAGE_RW -> PP msb */
 	rlwinm	r0,r5,32-6,30,30	/* _PAGE_DIRTY -> PP msb */
-	and	r8,r5,r0		/* writable if _RW & _DIRTY */
-	rlwimi	r5,r5,1,30,30		/* _PAGE_USER -> PP msb */
+	and	r8,r8,r0		/* writable if _RW & _DIRTY */
+	rlwimi	r5,r5,32-1,30,30	/* _PAGE_USER -> PP msb */
+	rlwimi	r5,r5,32-2,31,31	/* _PAGE_USER -> PP lsb */
 	ori	r8,r8,0xe04		/* clear out reserved bits */
 	andc	r8,r5,r8		/* PP = user? (rw&dirty? 1: 3): 0 */
 BEGIN_FTR_SECTION
@@ -564,7 +566,7 @@ _GLOBAL(flush_hash_pages)
 33:	lwarx	r8,0,r5			/* fetch the pte flags word */
 	andi.	r0,r8,_PAGE_HASHPTE
 	beq	8f			/* done if HASHPTE is already clear */
-	rlwinm	r8,r8,0,~_PAGE_HASHPTE	/* clear HASHPTE bit */
+	rlwinm	r8,r8,0,31,29		/* clear HASHPTE bit */
 	stwcx.	r8,0,r5			/* update the pte */
 	bne-	33b