Index: common/lib/libc/arch/powerpc/atomic/atomic_cas.S
===================================================================
RCS file: /home/netbsd/src/common/lib/libc/arch/powerpc/atomic/atomic_cas.S,v
retrieving revision 1.8
diff -p -u -r1.8 atomic_cas.S
--- common/lib/libc/arch/powerpc/atomic/atomic_cas.S	7 Mar 2014 07:17:54 -0000	1.8
+++ common/lib/libc/arch/powerpc/atomic/atomic_cas.S	18 Feb 2020 02:37:59 -0000
@@ -39,6 +39,7 @@ ENTRY(_atomic_cas_32)
 1:	lwarx	%r3,0,%r10
 	cmpw	%r3,%r4
 	bnelr-
+	IBM405_ERRATA77_DCBT(0,%r10)
 	stwcx.	%r5,0,%r10
 	beqlr+
 	b	1b
Index: common/lib/libc/arch/powerpc/atomic/atomic_op_asm.h
===================================================================
RCS file: /home/netbsd/src/common/lib/libc/arch/powerpc/atomic/atomic_op_asm.h,v
retrieving revision 1.6
diff -p -u -r1.6 atomic_op_asm.h
--- common/lib/libc/arch/powerpc/atomic/atomic_op_asm.h	7 Mar 2014 07:17:54 -0000	1.6
+++ common/lib/libc/arch/powerpc/atomic/atomic_op_asm.h	18 Feb 2020 02:37:59 -0000
@@ -49,6 +49,7 @@ ENTRY(_atomic_##op##_32)	; \
 	mr	%r10,%r3	; \
 1:	lwarx	%r3,0,%r10	; \
 	insn	%r5,%r3,arg	; \
+	IBM405_ERRATA77_DCBT(0,%r10) ; \
 	stwcx.	%r5,0,%r10	; \
 	beqlr+			; \
 	b	1b		; \
@@ -71,6 +72,7 @@ ENTRY(_atomic_##op##_32_nv)	; \
 	mr	%r10,%r3	; \
 1:	lwarx	%r3,0,%r10	; \
 	insn	%r3,%r3,arg	; \
+	IBM405_ERRATA77_DCBT(0,%r10) ; \
 	stwcx.	%r3,0,%r10	; \
 	beqlr+			; \
 	b	1b		; \
Index: common/lib/libc/arch/powerpc/atomic/atomic_swap.S
===================================================================
RCS file: /home/netbsd/src/common/lib/libc/arch/powerpc/atomic/atomic_swap.S,v
retrieving revision 1.7
diff -p -u -r1.7 atomic_swap.S
--- common/lib/libc/arch/powerpc/atomic/atomic_swap.S	7 Mar 2014 07:17:54 -0000	1.7
+++ common/lib/libc/arch/powerpc/atomic/atomic_swap.S	18 Feb 2020 02:37:59 -0000
@@ -37,6 +37,7 @@ __RCSID("$NetBSD: atomic_swap.S,v 1.7 20
 ENTRY(_atomic_swap_32)
 	mr	%r10,%r3
 1:	lwarx	%r3,0,%r10
+	IBM405_ERRATA77_DCBT(0,%r10)
 	stwcx.	%r4,0,%r10
 	beqlr+
 	b	1b
Index: sys/arch/evbppc/conf/std.obs200
===================================================================
RCS file: /home/netbsd/src/sys/arch/evbppc/conf/std.obs200,v
retrieving revision 1.4
diff -p -u -r1.4 std.obs200
--- sys/arch/evbppc/conf/std.obs200	18 Mar 2010 14:15:38 -0000	1.4
+++ sys/arch/evbppc/conf/std.obs200	21 Feb 2020 00:17:20 -0000
@@ -4,6 +4,8 @@
 
 include		"arch/evbppc/conf/std.obs405"
 
+options 	IBM405_ERRATA77
+
 makeoptions	PRDCTTYPE="obs200"
 makeoptions	TEXTADDR=0x450000
 options 	KERNBASE=0x450000
Index: sys/arch/evbppc/conf/std.obs266
===================================================================
RCS file: /home/netbsd/src/sys/arch/evbppc/conf/std.obs266,v
retrieving revision 1.2
diff -p -u -r1.2 std.obs266
--- sys/arch/evbppc/conf/std.obs266	4 Apr 2011 19:55:16 -0000	1.2
+++ sys/arch/evbppc/conf/std.obs266	18 Feb 2020 02:37:59 -0000
@@ -4,6 +4,8 @@
 
 include		"arch/evbppc/conf/std.obs405"
 
+options 	IBM405_ERRATA77
+
 makeoptions	PRDCTTYPE="obs266"
 makeoptions	TEXTADDR=0x25000
 options 	KERNBASE=0x25000
Index: sys/arch/evbppc/conf/std.virtex
===================================================================
RCS file: /home/netbsd/src/sys/arch/evbppc/conf/std.virtex,v
retrieving revision 1.3
diff -p -u -r1.3 std.virtex
--- sys/arch/evbppc/conf/std.virtex	20 Jun 2011 17:44:33 -0000	1.3
+++ sys/arch/evbppc/conf/std.virtex	21 Feb 2020 00:27:54 -0000
@@ -8,6 +8,10 @@ include		"conf/std"	# MI standard option
 # standard ("mandatory") kernel options.
 options 	PPC_IBM4XX	# IBM 40x family
 
+# XXX According to Linux, 405D5 (Virtex-II Pro) is affected, whereas
+# XXX 405F6 (Virtex-4) is not.
+options 	IBM405_ERRATA77
+
 # Executable support:
 options 	EXEC_ELF32	# (native) ELF32 binary support
 options 	EXEC_AOUT	# (native) a.out binary support (deprecated)
Index: sys/arch/evbppc/conf/std.walnut
===================================================================
RCS file: /home/netbsd/src/sys/arch/evbppc/conf/std.walnut,v
retrieving revision 1.8
diff -p -u -r1.8 std.walnut
--- sys/arch/evbppc/conf/std.walnut	22 Jun 2011 18:06:32 -0000	1.8
+++ sys/arch/evbppc/conf/std.walnut	21 Feb 2020 00:22:13 -0000
@@ -8,6 +8,8 @@ include		"conf/std"	# MI standard option
 # standard ("mandatory") kernel options.
 options 	PPC_IBM4XX	# IBM 40x family
 
+options 	IBM405_ERRATA77
+
 # Executable support:
 options 	EXEC_ELF32	# (native) ELF32 binary support
 options 	EXEC_AOUT	# (native) a.out binary support (deprecated)
Index: sys/arch/powerpc/ibm4xx/4xx_trap_subr.S
===================================================================
RCS file: /home/netbsd/src/sys/arch/powerpc/ibm4xx/4xx_trap_subr.S,v
retrieving revision 1.7
diff -p -u -r1.7 4xx_trap_subr.S
--- sys/arch/powerpc/ibm4xx/4xx_trap_subr.S	19 May 2011 07:51:50 -0000	1.7
+++ sys/arch/powerpc/ibm4xx/4xx_trap_subr.S	18 Feb 2020 02:37:59 -0000
@@ -55,10 +55,12 @@ _C_LABEL(pitfitwdog):
 _C_LABEL(pitfitwdogsize) = .-_C_LABEL(pitfitwdog)
 
 pithandler:
+	IBM405_ERRATA77_SYNC
 	rfi
 	ba	.	/* Protect against prefetch */
 
 wdoghandler:
+	IBM405_ERRATA77_SYNC
 	rfi
 	ba	.	/* Protect against prefetch */
 
Index: sys/arch/powerpc/ibm4xx/trap_subr.S
===================================================================
RCS file: /home/netbsd/src/sys/arch/powerpc/ibm4xx/trap_subr.S,v
retrieving revision 1.27
diff -p -u -r1.27 trap_subr.S
--- sys/arch/powerpc/ibm4xx/trap_subr.S	15 Jul 2018 05:16:43 -0000	1.27
+++ sys/arch/powerpc/ibm4xx/trap_subr.S	18 Feb 2020 02:37:59 -0000
@@ -334,6 +334,7 @@ intrleave_to_kernel:
 	mtpid	%r31
 	mfsprg3	%r31
 	mfsprg2	%r30
+	IBM405_ERRATA77_SYNC
 	rfi
 	ba	.		/* Protect against prefetch */
 
@@ -375,6 +376,7 @@ intrleave_to_user:
 	mtpid	%r31
 	mfsprg3	%r31
 	mfsprg2	%r30
+	IBM405_ERRATA77_SYNC
 	rfi
 	ba	.	/* Protect against prefetch */
 
Index: sys/arch/powerpc/include/asm.h
===================================================================
RCS file: /home/netbsd/src/sys/arch/powerpc/include/asm.h,v
retrieving revision 1.48
diff -p -u -r1.48 asm.h
--- sys/arch/powerpc/include/asm.h	12 Jan 2015 02:32:33 -0000	1.48
+++ sys/arch/powerpc/include/asm.h	21 Feb 2020 00:43:16 -0000
@@ -432,4 +432,20 @@ y:	.quad	.##y,.TOC.@tocbase,0;	\
 .endm
 #endif /* _LOCORE */
 
+#if defined(IBM405_ERRATA77) || \
+    ((defined(_MODULE) || !defined(_KERNEL)) && !defined(__LP64__))
+/*
+ * Workaround for IBM405 Errata 77 (CPU_210): interrupted stwcx. may
+ * errantly write data to memory
+ *
+ * (1) Insert dcbt before every stwcx. instruction
+ * (2) Insert sync before every rfi/rfci instruction
+ */
+#define	IBM405_ERRATA77_DCBT(ra, rb)	dcbt ra,rb
+#define	IBM405_ERRATA77_SYNC		sync
+#else
+#define	IBM405_ERRATA77_DCBT(ra, rb)	/* nothing */
+#define	IBM405_ERRATA77_SYNC		/* nothing */
+#endif
+
 #endif /* !_PPC_ASM_H_ */
Index: sys/arch/powerpc/include/lock.h
===================================================================
RCS file: /home/netbsd/src/sys/arch/powerpc/include/lock.h,v
retrieving revision 1.14
diff -p -u -r1.14 lock.h
--- sys/arch/powerpc/include/lock.h	29 Nov 2019 20:05:59 -0000	1.14
+++ sys/arch/powerpc/include/lock.h	18 Feb 2020 02:37:59 -0000
@@ -80,7 +80,11 @@ __cpu_simple_lock(__cpu_simple_lock_t *a
 2:	lwzx	%0,0,%1		\n\
 	cmpwi	%0,%2		\n\
 	beq+	1b		\n\
-	b	2b		\n\
+	b	2b		\n"
+#ifdef IBM405_ERRATA77
+	"dcbt	0,%1		\n"
+#endif
+"				\
 3:	stwcx.	%3,0,%1		\n\
 	bne-	1b		\n\
 	isync			\n\
@@ -99,9 +103,16 @@ __cpu_simple_lock_try(__cpu_simple_lock_
 				\n\
 1:	lwarx	%0,0,%1		\n\
 	cmpwi	%0,%2		\n\
-	bne	2f		\n\
-	stwcx.	%3,0,%1		\n\
-	bne-	1b		\n\
+	bne	2f		\n"
+#ifdef IBM405_ERRATA77
+	"dcbt	0,%1		\n"
+#endif
+	"stwcx.	%3,0,%1		\n\
+	bne-	1b		\n"
+#ifdef IBM405_ERRATA77
+	"dcbt	0,%4		\n"
+#endif
+"				\
 2:	stwcx.	%3,0,%4		\n\
 	isync			\n\
 				\n"
Index: sys/arch/powerpc/powerpc/lock_stubs.S
===================================================================
RCS file: /home/netbsd/src/sys/arch/powerpc/powerpc/lock_stubs.S,v
retrieving revision 1.11
diff -p -u -r1.11 lock_stubs.S
--- sys/arch/powerpc/powerpc/lock_stubs.S	21 Jan 2020 04:30:14 -0000	1.11
+++ sys/arch/powerpc/powerpc/lock_stubs.S	18 Feb 2020 02:37:59 -0000
@@ -55,6 +55,7 @@ ENTRY(_lock_cas)
 	lptrarx	%r10,0,%r3
 	cmpptr	%r10,%r4
 	bne-	2f
+	IBM405_ERRATA77_DCBT(0,%r3)
 	stptrcx. %r5,0,%r3
 	bne-	1b
 	SYNC
@@ -73,6 +74,7 @@ ENTRY(mutex_enter)
 	lptrarx	%r10,0,%r3
 	cmpptri	%r10,0
 	bne-	2f
+	IBM405_ERRATA77_DCBT(0,%r3)
 	stptrcx. %r13,0,%r3
 	bne-	1b
 	ISYNC
@@ -90,6 +92,7 @@ ENTRY(mutex_exit)
 	lptrarx	%r10,0,%r3
 	cmpptr	%r10,%r13
 	bne-	2f
+	IBM405_ERRATA77_DCBT(0,%r3)
 	stptrcx. %r7,0,%r3
 	bne-	1b
 	blr
@@ -125,6 +128,7 @@ ENTRY(rw_enter)
 2:	lptrarx	%r10,0,%r3
 	cmpptr	%r10,%r9
 	bne-	3f
+	IBM405_ERRATA77_DCBT(0,%r3)
 	stptrcx. %r7,0,%r3
 	bne-	2b
 	ISYNC
@@ -150,6 +154,7 @@ ENTRY(rw_tryenter)
 2:	lptrarx	%r10,0,%r3
 	cmpptr	%r10,%r9
 	bne-	3f
+	IBM405_ERRATA77_DCBT(0,%r3)
 	stptrcx. %r7,0,%r3
 	bne-	2b
 
@@ -181,6 +186,7 @@ ENTRY(rw_exit)
 2:	lptrarx	%r10,0,%r3
 	cmpptr	%r10,%r9
 	bne-	3f
+	IBM405_ERRATA77_DCBT(0,%r3)
 	stptrcx. %r7,0,%r3
 	bne-	2b
 
Index: sys/arch/powerpc/powerpc/locore_subr.S
===================================================================
RCS file: /home/netbsd/src/sys/arch/powerpc/powerpc/locore_subr.S,v
retrieving revision 1.59
diff -p -u -r1.59 locore_subr.S
--- sys/arch/powerpc/powerpc/locore_subr.S	8 Jan 2020 20:59:19 -0000	1.59
+++ sys/arch/powerpc/powerpc/locore_subr.S	18 Feb 2020 02:37:59 -0000
@@ -281,6 +281,7 @@ ENTRY(cpu_switchto)
  */
 	ldreg	%r31,CFRAME_R31(%r1)	/* restore saved registers */
 	ldreg	%r30,CFRAME_R30(%r1)
+	IBM405_ERRATA77_DCBT(0,%r1)
 	stwcx.	%r1,0,%r1		/* clear reservation */
 #if 1
 	addi	%r1,%r1,CALLFRAMELEN
@@ -320,6 +321,7 @@ _ENTRY(softint_cleanup)
 	mtmsr	%r0
 	isync
 #endif
+	IBM405_ERRATA77_DCBT(0,%r1)
 	stwcx.	%r1,0,%r1		/* clear reservation */
 	addi	%r1, %r1, CALLFRAMELEN
 	ldreg	%r0, CFRAME_LR(%r1)
@@ -471,6 +473,7 @@ _ENTRY(softint_fast_dispatch)
 	ldreg	%r29,SFRAME_R29(%r1)	/* R29 */
 	ldreg	%r31,SFRAMELEN+CFRAME_R31(%r1)	/* restore saved registers */
 	ldreg	%r30,SFRAMELEN+CFRAME_R30(%r1)
+	IBM405_ERRATA77_DCBT(0,%r1)
 	stwcx.	%r1,0,%r1		/* clear reservation */
 	addi	%r1,%r1,SFRAMELEN+2*CALLFRAMELEN /* remove switch & callframes */
 #endif
@@ -578,6 +581,7 @@ ENTRY(do_ucas_32)
 	lwarx	%r10,0,%r3
 	cmpw	%r10, %r4
 	bne	2f
+	IBM405_ERRATA77_DCBT(0,%r3)
 	stwcx.	%r5,0,%r3
 	bne	1b
 	mr	%r5,%r10
Index: sys/arch/powerpc/powerpc/trap_subr.S
===================================================================
RCS file: /home/netbsd/src/sys/arch/powerpc/powerpc/trap_subr.S,v
retrieving revision 1.80
diff -p -u -r1.80 trap_subr.S
--- sys/arch/powerpc/powerpc/trap_subr.S	15 Jul 2018 05:16:44 -0000	1.80
+++ sys/arch/powerpc/powerpc/trap_subr.S	18 Feb 2020 02:37:59 -0000
@@ -315,6 +315,7 @@ dsitrap_fix_dbat7:
 	ldreg	%r30,(CI_DISISAVE+CPUSAVE_R30)(%r1)	/* restore r30 */
 	ldreg	%r31,(CI_DISISAVE+CPUSAVE_R31)(%r1)	/* restore r31 */
 	mfsprg1	%r1
+	IBM405_ERRATA77_SYNC
 	RFI				/* return to trapped code */
 1:
 #endif	/* !PPC_MPC8XX */
@@ -387,6 +388,7 @@ _C_LABEL(dsi601trap):
 	ldreg	%r30,(CI_DISISAVE+CPUSAVE_R30)(%r1)	/* restore r30 */
 	ldreg	%r31,(CI_DISISAVE+CPUSAVE_R31)(%r1)	/* restore r31 */
 	mfsprg1	%r1
+	IBM405_ERRATA77_SYNC
 	RFI				/* return to trapped code */
 1:
 	mflr	%r28			/* save LR */
@@ -503,6 +505,7 @@ _C_LABEL(tlbimiss):
 	srwi	%r1,%r1,8		/* get byte 7 of pte */
 	tlbli	%r0			/* load the itlb */
 	stb	%r1,6(%r2)		/* update page table */
+	IBM405_ERRATA77_SYNC
 	RFI
 
 3:	/* not found in pteg */
@@ -562,6 +565,7 @@ _C_LABEL(tlbdlmiss):
 	srwi	%r1,%r1,8		/* get byte 7 of pte */
 	tlbld	%r0			/* load the dtlb */
 	stb	%r1,6(%r2)		/* update page table */
+	IBM405_ERRATA77_SYNC
 	RFI
 
 3:	/* not found in pteg */
@@ -618,6 +622,7 @@ _C_LABEL(tlbdsmiss):
 	mtcrf	0x80,%r3		/* and restore */
 	mtspr	SPR_RPA,%r1		/* set the pte */
 	tlbld	%r0			/* load the dtlb */
+	IBM405_ERRATA77_SYNC
 	RFI
 
 3:	/* not found in pteg */
@@ -991,6 +996,7 @@ trapleave:
 	FRAME_RESTORE_CALLEE
 intrleave:
 	FRAME_LEAVE(CI_TEMPSAVE)
+	IBM405_ERRATA77_SYNC
 	RFI
 
 /*
@@ -1214,6 +1220,7 @@ ddbtrap:
 	beq	trapagain
 	FRAME_RESTORE_CALLEE
 	FRAME_LEAVE(CI_DDBSAVE)
+	IBM405_ERRATA77_SYNC
 	RFI
 #endif /* DDB || KGDB */