Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Message-Id: <3ad4c8a52bb1f21da9acff41375ed098fcfdf0ee.1548419273.git.christophe.leroy@c-s.fr>
In-Reply-To: <cover.1548419273.git.christophe.leroy@c-s.fr>
References: <cover.1548419273.git.christophe.leroy@c-s.fr>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [PATCH 09/10] powerpc/603: don't handle PAGE_ACCESSED in TLB miss
 handlers.
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        joakim.tjernlund@infinera.com
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Date:   Fri, 25 Jan 2019 12:34:18 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

PAGE_ACCESSED is only needed for CONFIG_SWAP. When CONFIG_SWAP
is not set, just ignore it. If CONFIG_SWAP is set and PAGE_ACCESSED
is not, let's take a minor fault.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/head_32.S | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 44cc84857520..9f25f44b6448 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -505,7 +505,11 @@ InstructionTLBMiss:
 	cmplw	0,r1,r3
 #endif
 	mfspr	r2, SPRN_SPRG_603_PGDIR
+#ifdef CONFIG_SWAP
+	li	r1,_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_EXEC
+#else
 	li	r1,_PAGE_PRESENT | _PAGE_EXEC
+#endif
 #if defined(CONFIG_MODULES) || defined(CONFIG_DEBUG_PAGEALLOC)
 	bge-	112f
 	lis	r2, (swapper_pg_dir - PAGE_OFFSET)@ha	/* if kernel address, use */
@@ -519,12 +523,6 @@ InstructionTLBMiss:
 	lwz	r0,0(r2)		/* get linux-style pte */
 	andc.	r1,r1,r0		/* check access & ~permission */
 	bne-	InstructionAddressInvalid /* return if access not permitted */
-	ori	r0,r0,_PAGE_ACCESSED	/* set _PAGE_ACCESSED in pte */
-	/*
-	 * NOTE! We are assuming this is not an SMP system, otherwise
-	 * we would need to update the pte atomically with lwarx/stwcx.
-	 */
-	stw	r0,0(r2)		/* update PTE (accessed bit) */
 	/* Convert linux-style PTE to low word of PPC-style PTE */
 	rlwimi	r0,r0,32-1,30,30	/* _PAGE_USER -> PP msb */
 	ori	r1, r1, 0xe05		/* clear out reserved bits */
@@ -573,7 +571,11 @@ DataLoadTLBMiss:
 	lis	r1,PAGE_OFFSET@h		/* check if kernel address */
 	cmplw	0,r1,r3
 	mfspr	r2, SPRN_SPRG_603_PGDIR
+#ifdef CONFIG_SWAP
+	li	r1, _PAGE_PRESENT | _PAGE_ACCESSED
+#else
 	li	r1, _PAGE_PRESENT
+#endif
 	bge-	112f
 	lis	r2, (swapper_pg_dir - PAGE_OFFSET)@ha	/* if kernel address, use */
 	addi	r2, r2, (swapper_pg_dir - PAGE_OFFSET)@l	/* kernel page table */
@@ -585,12 +587,10 @@ DataLoadTLBMiss:
 	lwz	r0,0(r2)		/* get linux-style pte */
 	andc.	r1,r1,r0		/* check access & ~permission */
 	bne-	DataAddressInvalid	/* return if access not permitted */
-	ori	r0,r0,_PAGE_ACCESSED	/* set _PAGE_ACCESSED in pte */
 	/*
 	 * NOTE! We are assuming this is not an SMP system, otherwise
 	 * we would need to update the pte atomically with lwarx/stwcx.
 	 */
-	stw	r0,0(r2)		/* update PTE (accessed bit) */
 	/* Convert linux-style PTE to low word of PPC-style PTE */
 	rlwinm	r1,r0,32-10,31,31	/* _PAGE_RW -> PP lsb */
 	rlwimi	r0,r0,32-1,30,30	/* _PAGE_USER -> PP msb */
@@ -651,7 +651,11 @@ DataStoreTLBMiss:
 	lis	r1,PAGE_OFFSET@h		/* check if kernel address */
 	cmplw	0,r1,r3
 	mfspr	r2, SPRN_SPRG_603_PGDIR
-	li	r1, _PAGE_RW | _PAGE_PRESENT /* access flags */
+#ifdef CONFIG_SWAP
+	li	r1, _PAGE_RW | _PAGE_PRESENT | _PAGE_ACCESSED
+#else
+	li	r1, _PAGE_RW | _PAGE_PRESENT
+#endif
 	bge-	112f
 	lis	r2, (swapper_pg_dir - PAGE_OFFSET)@ha	/* if kernel address, use */
 	addi	r2, r2, (swapper_pg_dir - PAGE_OFFSET)@l	/* kernel page table */
@@ -663,12 +667,10 @@ DataStoreTLBMiss:
 	lwz	r0,0(r2)		/* get linux-style pte */
 	andc.	r1,r1,r0		/* check access & ~permission */
 	bne-	DataAddressInvalid	/* return if access not permitted */
-	ori	r0,r0,_PAGE_ACCESSED
 	/*
 	 * NOTE! We are assuming this is not an SMP system, otherwise
 	 * we would need to update the pte atomically with lwarx/stwcx.
 	 */
-	stw	r0,0(r2)		/* update PTE (accessed/dirty bits) */
 	/* Convert linux-style PTE to low word of PPC-style PTE */
 	rlwimi	r0,r0,32-1,30,30	/* _PAGE_USER -> PP msb */
 	li	r1,0xe05		/* clear out reserved bits & PP lsb */
-- 
2.13.3