diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
index 78b257b7..b0052848 100644
--- a/lib/s390x/asm/arch_def.h
+++ b/lib/s390x/asm/arch_def.h
@@ -46,9 +46,10 @@ struct psw {
 #define AS_SECN				2
 #define AS_HOME				3
 
-#define PSW_MASK_EXT			0x0100000000000000UL
-#define PSW_MASK_IO			0x0200000000000000UL
 #define PSW_MASK_DAT			0x0400000000000000UL
+#define PSW_MASK_IO			0x0200000000000000UL
+#define PSW_MASK_EXT			0x0100000000000000UL
+#define PSW_MASK_KEY			0x00F0000000000000UL
 #define PSW_MASK_WAIT			0x0002000000000000UL
 #define PSW_MASK_PSTATE			0x0001000000000000UL
 #define PSW_MASK_EA			0x0000000100000000UL
@@ -313,6 +314,53 @@ static inline void load_psw_mask(uint64_t mask)
 		: "+r" (tmp) :  "a" (&psw) : "memory", "cc" );
 }
 
+/**
+ * psw_mask_set_clear_bits - sets and clears bits from the current PSW mask
+ * @clear: bitmask of bits that will be cleared
+ * @set: bitmask of bits that will be set
+ *
+ * Bits will be cleared first, and then set, so if (@clear & @set != 0) then
+ * the bits in the intersection will be set.
+ */
+static inline void psw_mask_set_clear_bits(uint64_t clear, uint64_t set)
+{
+	load_psw_mask((extract_psw_mask() & ~clear) | set);
+}
+
+/**
+ * psw_mask_clear_bits - clears bits from the current PSW mask
+ * @clear: bitmask of bits that will be cleared
+ */
+static inline void psw_mask_clear_bits(uint64_t clear)
+{
+	load_psw_mask(extract_psw_mask() & ~clear);
+}
+
+/**
+ * psw_mask_set_bits - sets bits on the current PSW mask
+ * @set: bitmask of bits that will be set
+ */
+static inline void psw_mask_set_bits(uint64_t set)
+{
+	load_psw_mask(extract_psw_mask() | set);
+}
+
+/**
+ * enable_dat - enable the DAT bit in the current PSW
+ */
+static inline void enable_dat(void)
+{
+	psw_mask_set_bits(PSW_MASK_DAT);
+}
+
+/**
+ * disable_dat - disable the DAT bit in the current PSW
+ */
+static inline void disable_dat(void)
+{
+	psw_mask_clear_bits(PSW_MASK_DAT);
+}
+
 static inline void wait_for_interrupt(uint64_t irq_mask)
 {
 	uint64_t psw_mask = extract_psw_mask();
@@ -327,11 +375,7 @@ static inline void wait_for_interrupt(uint64_t irq_mask)
 
 static inline void enter_pstate(void)
 {
-	uint64_t mask;
-
-	mask = extract_psw_mask();
-	mask |= PSW_MASK_PSTATE;
-	load_psw_mask(mask);
+	psw_mask_set_bits(PSW_MASK_PSTATE);
 }
 
 static inline void leave_pstate(void)
diff --git a/lib/s390x/asm/pgtable.h b/lib/s390x/asm/pgtable.h
index f166dcc6..7b556ad9 100644
--- a/lib/s390x/asm/pgtable.h
+++ b/lib/s390x/asm/pgtable.h
@@ -247,6 +247,4 @@ static inline void idte_pgdp(unsigned long vaddr, pgdval_t *pgdp)
 	idte((unsigned long)(pgdp - pgd_index(vaddr)) | ASCE_DT_REGION1, vaddr);
 }
 
-void configure_dat(int enable);
-
 #endif /* _ASMS390X_PGTABLE_H_ */
diff --git a/lib/s390x/mmu.c b/lib/s390x/mmu.c
index c9f8754c..b474d702 100644
--- a/lib/s390x/mmu.c
+++ b/lib/s390x/mmu.c
@@ -29,18 +29,6 @@
 
 static pgd_t *table_root;
 
-void configure_dat(int enable)
-{
-	uint64_t mask;
-
-	if (enable)
-		mask = extract_psw_mask() | PSW_MASK_DAT;
-	else
-		mask = extract_psw_mask() & ~PSW_MASK_DAT;
-
-	load_psw_mask(mask);
-}
-
 static void mmu_enable(pgd_t *pgtable)
 {
 	const uint64_t asce = __pa(pgtable) | ASCE_DT_REGION1 |
@@ -51,7 +39,7 @@ static void mmu_enable(pgd_t *pgtable)
 	assert(stctg(1) == asce);
 
 	/* enable dat (primary == 0 set as default) */
-	configure_dat(1);
+	enable_dat();
 
 	/* we can now also use DAT unconditionally in our PGM handler */
 	lowcore.pgm_new_psw.mask |= PSW_MASK_DAT;
diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
index b8204c5f..a806cdb3 100644
--- a/lib/s390x/sclp.c
+++ b/lib/s390x/sclp.c
@@ -48,13 +48,8 @@ static void mem_init(phys_addr_t mem_end)
 
 void sclp_setup_int(void)
 {
-	uint64_t mask;
-
 	ctl_set_bit(0, CTL0_SERVICE_SIGNAL);
-
-	mask = extract_psw_mask();
-	mask |= PSW_MASK_EXT;
-	load_psw_mask(mask);
+	psw_mask_set_bits(PSW_MASK_EXT);
 }
 
 void sclp_handle_ext(void)
diff --git a/s390x/diag288.c b/s390x/diag288.c
index e414865b..46dc0ed8 100644
--- a/s390x/diag288.c
+++ b/s390x/diag288.c
@@ -78,16 +78,14 @@ static void test_priv(void)
 
 static void test_bite(void)
 {
-	uint64_t mask, time;
+	uint64_t time;
 
 	/* If watchdog doesn't bite, the cpu timer does */
 	asm volatile("stck %0" : "=Q" (time) : : "cc");
 	time += (uint64_t)(16000 * 1000) << 12;
 	asm volatile("sckc %0" : : "Q" (time));
 	ctl_set_bit(0, CTL0_CLOCK_COMPARATOR);
-	mask = extract_psw_mask();
-	mask |= PSW_MASK_EXT;
-	load_psw_mask(mask);
+	psw_mask_set_bits(PSW_MASK_EXT);
 
 	/* Arm watchdog */
 	lowcore.restart_new_psw.mask = extract_psw_mask() & ~PSW_MASK_EXT;
diff --git a/s390x/selftest.c b/s390x/selftest.c
index 239bc5e3..13fd36bc 100644
--- a/s390x/selftest.c
+++ b/s390x/selftest.c
@@ -64,9 +64,9 @@ static void test_malloc(void)
 	report(tmp != tmp2, "allocated memory addresses differ");
 
 	expect_pgm_int();
-	configure_dat(0);
+	disable_dat();
 	*tmp = 987654321;
-	configure_dat(1);
+	enable_dat();
 	check_pgm_int_code(PGM_INT_CODE_ADDRESSING);
 
 	free(tmp);
diff --git a/s390x/skrf.c b/s390x/skrf.c
index 1a811894..26f70b4e 100644
--- a/s390x/skrf.c
+++ b/s390x/skrf.c
@@ -63,11 +63,9 @@ static void test_pfmf(void)
 
 static void test_psw_key(void)
 {
-	uint64_t psw_mask = extract_psw_mask() | 0xF0000000000000UL;
-
 	report_prefix_push("psw key");
 	expect_pgm_int();
-	load_psw_mask(psw_mask);
+	psw_mask_set_bits(PSW_MASK_KEY);
 	check_pgm_int_code(PGM_INT_CODE_SPECIAL_OPERATION);
 	report_prefix_pop();
 }
@@ -140,17 +138,13 @@ static void ecall_cleanup(void)
 /* Set a key into the external new psw mask and open external call masks */
 static void ecall_setup(void)
 {
-	uint64_t mask;
-
 	register_pgm_cleanup_func(ecall_cleanup);
 	expect_pgm_int();
 	/* Put a skey into the ext new psw */
-	lowcore.ext_new_psw.mask = 0x00F0000000000000UL | PSW_MASK_64;
+	lowcore.ext_new_psw.mask = PSW_MASK_KEY | PSW_MASK_64;
 	/* Open up ext masks */
 	ctl_set_bit(0, CTL0_EXTERNAL_CALL);
-	mask = extract_psw_mask();
-	mask |= PSW_MASK_EXT;
-	load_psw_mask(mask);
+	psw_mask_set_bits(PSW_MASK_EXT);
 	/* Tell cpu 0 that we're ready */
 	set_flag(1);
 }
diff --git a/s390x/smp.c b/s390x/smp.c
index 6d474d0d..0df4751f 100644
--- a/s390x/smp.c
+++ b/s390x/smp.c
@@ -288,13 +288,9 @@ static void test_set_prefix(void)
 
 static void ecall(void)
 {
-	unsigned long mask;
-
 	expect_ext_int();
 	ctl_set_bit(0, CTL0_EXTERNAL_CALL);
-	mask = extract_psw_mask();
-	mask |= PSW_MASK_EXT;
-	load_psw_mask(mask);
+	psw_mask_set_bits(PSW_MASK_EXT);
 	set_flag(1);
 	while (lowcore.ext_int_code != 0x1202) { mb(); }
 	report_pass("received");
@@ -321,13 +317,9 @@ static void test_ecall(void)
 
 static void emcall(void)
 {
-	unsigned long mask;
-
 	expect_ext_int();
 	ctl_set_bit(0, CTL0_EMERGENCY_SIGNAL);
-	mask = extract_psw_mask();
-	mask |= PSW_MASK_EXT;
-	load_psw_mask(mask);
+	psw_mask_set_bits(PSW_MASK_EXT);
 	set_flag(1);
 	while (lowcore.ext_int_code != 0x1201) { mb(); }
 	report_pass("received");
@@ -466,14 +458,10 @@ static void test_reset_initial(void)
 
 static void test_local_ints(void)
 {
-	unsigned long mask;
-
 	/* Open masks for ecall and emcall */
 	ctl_set_bit(0, CTL0_EXTERNAL_CALL);
 	ctl_set_bit(0, CTL0_EMERGENCY_SIGNAL);
-	mask = extract_psw_mask();
-	mask |= PSW_MASK_EXT;
-	load_psw_mask(mask);
+	psw_mask_set_bits(PSW_MASK_EXT);
 	set_flag(1);
 }
 
