linux-kernel - [RFC PATCH v1 14/41] powerpc/32: Tag DAR in EXCEPTION_PROLOG

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Message-Id: <0b745d361b3c4891c6f23e80f7e629b3354f8671.1612864003.git.christophe.leroy@csgroup.eu>
Date:   Tue,  9 Feb 2021 09:56:38 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, npiggin@...il.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [RFC PATCH v1 14/41] powerpc/32: Tag DAR in EXCEPTION_PROLOG_2 for
 the 8xx

8xx requires to tag the DAR with a magic value in order to
detect fixup DAR on faults generated by 'dcbX', as the 8xx
forgets to update the DAR for those faults.

Do the tagging as early as possible, that is before enabling MMU.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/kernel/head_32.h  |  6 ++++++
 arch/powerpc/kernel/head_8xx.S | 18 ++++++------------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 1b707755c68e..910f86642eec 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -57,6 +57,12 @@
 .endm
 
 .macro EXCEPTION_PROLOG_2 handle_dar_dsisr=0
+#ifdef CONFIG_PPC_8xx
+	.if	\handle_dar_dsisr
+	li	r11, RPN_PATTERN
+	mtspr	SPRN_DAR, r11	/* Tag DAR, to be used in DTLB Error */
+	.endif
+#endif
 	LOAD_REG_IMMEDIATE(r11, MSR_KERNEL & ~(MSR_IR | MSR_RI)) /* can take DTLB miss */
 	mtmsr	r11
 	isync
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 792e2fd86479..cdbfa9d41353 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -30,6 +30,12 @@
 #include <asm/export.h>
 #include <asm/code-patching-asm.h>
 
+/*
+ * Value for the bits that have fixed value in RPN entries.
+ * Also used for tagging DAR for DTLBerror.
+ */
+#define RPN_PATTERN	0x00f0
+
 #include "head_32.h"
 
 .macro compare_to_kernel_boundary scratch, addr
@@ -42,12 +48,6 @@
 #endif
 .endm
 
-/*
- * Value for the bits that have fixed value in RPN entries.
- * Also used for tagging DAR for DTLBerror.
- */
-#define RPN_PATTERN	0x00f0
-
 #define PAGE_SHIFT_512K		19
 #define PAGE_SHIFT_8M		23
 
@@ -124,8 +124,6 @@ instruction_counter:
 	. = 0x200
 MachineCheck:
 	EXCEPTION_PROLOG handle_dar_dsisr=1
-	li	r6, RPN_PATTERN
-	mtspr	SPRN_DAR, r6	/* Tag DAR, to be used in DTLB Error */
 	addi r3,r1,STACK_FRAME_OVERHEAD
 	EXC_XFER_STD(0x200, machine_check_exception)
 
@@ -136,8 +134,6 @@ MachineCheck:
 	. = 0x600
 Alignment:
 	EXCEPTION_PROLOG handle_dar_dsisr=1
-	li	r6, RPN_PATTERN
-	mtspr	SPRN_DAR, r6	/* Tag DAR, to be used in DTLB Error */
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	b	.Lalignment_exception_ool
 
@@ -331,8 +327,6 @@ DataTLBError:
 	cmpwi	cr1, r11, RPN_PATTERN
 	beq-	cr1, FixupDAR	/* must be a buggy dcbX, icbi insn. */
 DARFixed:/* Return from dcbx instruction bug workaround */
-	li	r11, RPN_PATTERN
-	mtspr	SPRN_DAR, r11	/* Tag DAR, to be used in DTLB Error */
 	EXCEPTION_PROLOG_1
 	EXCEPTION_PROLOG_2 handle_dar_dsisr=1
 	lwz	r4, _DAR(r11)
-- 
2.25.0