diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index c2d5095..99c3c56 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -216,6 +216,7 @@ enum {
 #define CPU_FTR_PMAO_BUG		LONG_ASM_CONST(0x1000000000000000)
 #define CPU_FTR_SUBCORE			LONG_ASM_CONST(0x2000000000000000)
 #define CPU_FTR_POWER9_DD1		LONG_ASM_CONST(0x4000000000000000)
+#define CPU_FTR_LARGE_DEC		LONG_ASM_CONST(0x8000000000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -496,7 +497,8 @@ enum {
 	    (CPU_FTRS_POWER4 | CPU_FTRS_PPC970 | CPU_FTRS_POWER5 | \
 	     CPU_FTRS_POWER6 | CPU_FTRS_POWER7 | CPU_FTRS_POWER8E | \
 	     CPU_FTRS_POWER8 | CPU_FTRS_POWER8_DD1 | CPU_FTRS_CELL | \
-	     CPU_FTRS_PA6T | CPU_FTR_VSX | CPU_FTRS_POWER9 | CPU_FTRS_POWER9_DD1)
+	     CPU_FTRS_PA6T | CPU_FTR_VSX | CPU_FTRS_POWER9 | \
+	     CPU_FTRS_POWER9_DD1 | CPU_FTR_LARGE_DEC)
 #endif
 #else
 enum {
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 40c4887..987fcc5 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -259,6 +259,7 @@ static struct feature_property {
 	{"ibm,dfp", 1, 0, PPC_FEATURE_HAS_DFP},
 	{"ibm,purr", 1, CPU_FTR_PURR, 0},
 	{"ibm,spurr", 1, CPU_FTR_SPURR, 0},
+	{"ibm,dec-bits", 32, CPU_FTR_LARGE_DEC, 0},
 #endif /* CONFIG_PPC64 */
 };
 
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 2b33cfa..5d13f06 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -946,10 +946,7 @@ static void register_decrementer_clockevent(int cpu)
 
 static void enable_large_decrementer(void)
 {
-	if (!cpu_has_feature(CPU_FTR_ARCH_300))
-		return;
-
-	if (decrementer_max <= DECREMENTER_DEFAULT_MAX)
+	if (!cpu_has_feature(CPU_FTR_LARGE_DEC))
 		return;
 
 	/*
@@ -966,7 +963,7 @@ static void __init set_decrementer_max(void)
 	u32 bits = 32;
 
 	/* Prior to ISAv3 the decrementer is always 32 bit */
-	if (!cpu_has_feature(CPU_FTR_ARCH_300))
+	if (!cpu_has_feature(CPU_FTR_LARGE_DEC))
 		return;
 
 	cpu = of_find_node_by_type(NULL, "cpu");
diff --git a/arch/powerpc/kvm/book3s_hv_interrupts.S b/arch/powerpc/kvm/book3s_hv_interrupts.S
index 0fdc4a2..6e1d75f 100644
--- a/arch/powerpc/kvm/book3s_hv_interrupts.S
+++ b/arch/powerpc/kvm/book3s_hv_interrupts.S
@@ -124,7 +124,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 	mfspr	r8,SPRN_DEC
 	mftb	r7
 	mtspr	SPRN_HDEC,r8
+BEGIN_FTR_SECTION
 	extsw	r8,r8
+END_FTR_SECTION_IFCLR(CPU_FTR_LARGE_DEC)
 	add	r8,r8,r7
 	std	r8,HSTATE_DECEXP(r13)
 
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index bdb3f76..bcb5401 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -214,6 +214,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 kvmppc_primary_no_guest:
 	/* We handle this much like a ceded vcpu */
 	/* put the HDEC into the DEC, since HDEC interrupts don't wake us */
+	/* HDEC may be larger than DEC for arch >= v3.00, but since the */
+	/* HDEC value came from DEC in the first place, it will fit */
 	mfspr	r3, SPRN_HDEC
 	mtspr	SPRN_DEC, r3
 	/*
@@ -295,8 +297,11 @@ kvm_novcpu_wakeup:
 
 	/* See if our timeslice has expired (HDEC is negative) */
 	mfspr	r0, SPRN_HDEC
+BEGIN_FTR_SECTION
+	extsw	r0, r0
+END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
 	li	r12, BOOK3S_INTERRUPT_HV_DECREMENTER
-	cmpwi	r0, 0
+	cmpdi	r0, 0
 	blt	kvm_novcpu_exit
 
 	/* Got an IPI but other vcpus aren't yet exiting, must be a latecomer */
@@ -390,8 +395,8 @@ kvm_secondary_got_guest:
 	lbz	r4, HSTATE_PTID(r13)
 	cmpwi	r4, 0
 	bne	63f
-	lis	r6, 0x7fff
-	ori	r6, r6, 0xffff
+	LOAD_REG_ADDR(r6, decrementer_max)
+	ld	r6, 0(r6)
 	mtspr	SPRN_HDEC, r6
 	/* and set per-LPAR registers, if doing dynamic micro-threading */
 	ld	r6, HSTATE_SPLIT_MODE(r13)
@@ -968,7 +973,10 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300)
 
 	/* Check if HDEC expires soon */
 	mfspr	r3, SPRN_HDEC
-	cmpwi	r3, 512		/* 1 microsecond */
+BEGIN_FTR_SECTION
+	extsw	r3, r3
+END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
+	cmpdi	r3, 512		/* 1 microsecond */
 	blt	hdec_soon
 
 #ifdef CONFIG_KVM_XICS
@@ -2366,12 +2374,15 @@ END_FTR_SECTION_IFSET(CPU_FTR_TM)
 	mfspr	r3, SPRN_DEC
 	mfspr	r4, SPRN_HDEC
 	mftb	r5
-	cmpw	r3, r4
+	extsw	r3, r3
+BEGIN_FTR_SECTION
+	extsw	r4, r4
+END_FTR_SECTION_IFSET(CPU_FTR_LARGE_DEC)
+	cmpd	r3, r4
 	ble	67f
 	mtspr	SPRN_DEC, r4
 67:
 	/* save expiry time of guest decrementer */
-	extsw	r3, r3
 	add	r3, r3, r5
 	ld	r4, HSTATE_KVM_VCPU(r13)
 	ld	r5, HSTATE_KVM_VCORE(r13)
