diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 02f11018e2df1f99cfb4772088ec805be9c609cf..c6cf338c932704dd13a95af4e64ce2d50d940c13 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -189,10 +189,6 @@ ENTRY(__switch_to)
 	stg	%r3,__LC_CURRENT		# store task struct of next
 	stg	%r15,__LC_KERNEL_STACK		# store end of kernel stack
 	lg	%r15,__THREAD_ksp(%r1)		# load kernel stack of next
-	/* c4 is used in guest detection: arch/s390/kernel/perf_cpum_sf.c */
-	xc	__SF_EMPTY(8,%r15),__SF_EMPTY(%r15)
-	mvc	__SF_EMPTY+4(4,%r15),__TASK_pid(%r3)
-	lctlg	%c4,%c4,__SF_EMPTY(%r15)	# load pid to control reg. 4
 	mvc	__LC_CURRENT_PID(4,%r0),__TASK_pid(%r3) # store pid of next
 	lmg	%r6,%r15,__SF_GPRS(%r15)	# load gprs of next task
 	TSTMSK	__LC_MACHINE_FLAGS,MACHINE_FLAG_LPP
diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index 482d3526e32b290311151a17954f2c55ce41e15b..31c91f24e5624389b34017c45fd44dad3b11114f 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -52,7 +52,7 @@ ENTRY(startup_continue)
 	.quad	0			# cr1: primary space segment table
 	.quad	.Lduct			# cr2: dispatchable unit control table
 	.quad	0			# cr3: instruction authorization
-	.quad	0			# cr4: instruction authorization
+	.quad	0xffff			# cr4: instruction authorization
 	.quad	.Lduct			# cr5: primary-aste origin
 	.quad	0			# cr6:	I/O interrupts
 	.quad	0			# cr7:	secondary space segment table
diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index 1c0b58545c04d6f5c44e0f07838fcc35901e0cf5..9a4f279d25ca9675a711d604f0a9ec7c633cae7b 100644
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -1009,8 +1009,8 @@ static int perf_push_sample(struct perf_event *event, struct sf_raw_sample *sfr)
 	 * sample. Some early samples or samples from guests without
 	 * lpp usage would be misaccounted to the host. We use the asn
 	 * value as an addon heuristic to detect most of these guest samples.
-	 * If the value differs from the host hpp value, we assume to be a
-	 * KVM guest.
+	 * If the value differs from 0xffff (the host value), we assume to
+	 * be a KVM guest.
 	 */
 	switch (sfr->basic.CL) {
 	case 1: /* logical partition */
@@ -1020,8 +1020,7 @@ static int perf_push_sample(struct perf_event *event, struct sf_raw_sample *sfr)
 		sde_regs->in_guest = 1;
 		break;
 	default: /* old machine, use heuristics */
-		if (sfr->basic.gpp ||
-		    sfr->basic.prim_asn != (u16)sfr->basic.hpp)
+		if (sfr->basic.gpp || sfr->basic.prim_asn != 0xffff)
 			sde_regs->in_guest = 1;
 		break;
 	}