diff --git a/lib/s390x/smp.h b/lib/s390x/smp.h
index a2609f11..1e69a7de 100644
--- a/lib/s390x/smp.h
+++ b/lib/s390x/smp.h
@@ -37,15 +37,19 @@ struct cpu_status {
 
 int smp_query_num_cpus(void);
 struct cpu *smp_cpu_from_addr(uint16_t addr);
-bool smp_cpu_stopped(uint16_t addr);
-bool smp_sense_running_status(uint16_t addr);
-int smp_cpu_restart(uint16_t addr);
-int smp_cpu_start(uint16_t addr, struct psw psw);
-int smp_cpu_stop(uint16_t addr);
-int smp_cpu_stop_store_status(uint16_t addr);
-int smp_cpu_destroy(uint16_t addr);
-int smp_cpu_setup(uint16_t addr, struct psw psw);
+struct cpu *smp_cpu_from_idx(uint16_t idx);
+uint16_t smp_cpu_addr(uint16_t idx);
+bool smp_cpu_stopped(uint16_t idx);
+bool smp_sense_running_status(uint16_t idx);
+int smp_cpu_restart(uint16_t idx);
+int smp_cpu_start(uint16_t idx, struct psw psw);
+int smp_cpu_stop(uint16_t idx);
+int smp_cpu_stop_store_status(uint16_t idx);
+int smp_cpu_destroy(uint16_t idx);
+int smp_cpu_setup(uint16_t idx, struct psw psw);
 void smp_teardown(void);
 void smp_setup(void);
+int smp_sigp(uint16_t idx, uint8_t order, unsigned long parm, uint32_t *status);
+int smp_sigp_retry(uint16_t idx, uint8_t order, unsigned long parm, uint32_t *status);
 
 #endif
diff --git a/lib/s390x/smp.c b/lib/s390x/smp.c
index eae742d2..dde79274 100644
--- a/lib/s390x/smp.c
+++ b/lib/s390x/smp.c
@@ -29,11 +29,28 @@ static struct spinlock lock;
 
 extern void smp_cpu_setup_state(void);
 
+static void check_idx(uint16_t idx)
+{
+	assert(idx < smp_query_num_cpus());
+}
+
 int smp_query_num_cpus(void)
 {
 	return sclp_get_cpu_num();
 }
 
+int smp_sigp(uint16_t idx, uint8_t order, unsigned long parm, uint32_t *status)
+{
+	check_idx(idx);
+	return sigp(cpus[idx].addr, order, parm, status);
+}
+
+int smp_sigp_retry(uint16_t idx, uint8_t order, unsigned long parm, uint32_t *status)
+{
+	check_idx(idx);
+	return sigp_retry(cpus[idx].addr, order, parm, status);
+}
+
 struct cpu *smp_cpu_from_addr(uint16_t addr)
 {
 	int i, num = smp_query_num_cpus();
@@ -45,174 +62,183 @@ struct cpu *smp_cpu_from_addr(uint16_t addr)
 	return NULL;
 }
 
-bool smp_cpu_stopped(uint16_t addr)
+struct cpu *smp_cpu_from_idx(uint16_t idx)
+{
+	check_idx(idx);
+	return &cpus[idx];
+}
+
+uint16_t smp_cpu_addr(uint16_t idx)
+{
+	check_idx(idx);
+	return cpus[idx].addr;
+}
+
+bool smp_cpu_stopped(uint16_t idx)
 {
 	uint32_t status;
 
-	if (sigp(addr, SIGP_SENSE, 0, &status) != SIGP_CC_STATUS_STORED)
+	if (smp_sigp(idx, SIGP_SENSE, 0, &status) != SIGP_CC_STATUS_STORED)
 		return false;
 	return !!(status & (SIGP_STATUS_CHECK_STOP|SIGP_STATUS_STOPPED));
 }
 
-bool smp_sense_running_status(uint16_t addr)
+bool smp_sense_running_status(uint16_t idx)
 {
-	if (sigp(addr, SIGP_SENSE_RUNNING, 0, NULL) != SIGP_CC_STATUS_STORED)
+	if (smp_sigp(idx, SIGP_SENSE_RUNNING, 0, NULL) != SIGP_CC_STATUS_STORED)
 		return true;
 	/* Status stored condition code is equivalent to cpu not running. */
 	return false;
 }
 
-static int smp_cpu_stop_nolock(uint16_t addr, bool store)
+static int smp_cpu_stop_nolock(uint16_t idx, bool store)
 {
-	struct cpu *cpu;
 	uint8_t order = store ? SIGP_STOP_AND_STORE_STATUS : SIGP_STOP;
 
-	cpu = smp_cpu_from_addr(addr);
-	if (!cpu || addr == cpus[0].addr)
+	/* refuse to work on the boot CPU */
+	if (idx == 0)
 		return -1;
 
-	if (sigp_retry(addr, order, 0, NULL))
+	if (smp_sigp_retry(idx, order, 0, NULL))
 		return -1;
 
-	while (!smp_cpu_stopped(addr))
+	while (!smp_cpu_stopped(idx))
 		mb();
-	cpu->active = false;
+	/* idx has been already checked by the smp_* functions called above */
+	cpus[idx].active = false;
 	return 0;
 }
 
-int smp_cpu_stop(uint16_t addr)
+int smp_cpu_stop(uint16_t idx)
 {
 	int rc;
 
 	spin_lock(&lock);
-	rc = smp_cpu_stop_nolock(addr, false);
+	rc = smp_cpu_stop_nolock(idx, false);
 	spin_unlock(&lock);
 	return rc;
 }
 
-int smp_cpu_stop_store_status(uint16_t addr)
+int smp_cpu_stop_store_status(uint16_t idx)
 {
 	int rc;
 
 	spin_lock(&lock);
-	rc = smp_cpu_stop_nolock(addr, true);
+	rc = smp_cpu_stop_nolock(idx, true);
 	spin_unlock(&lock);
 	return rc;
 }
 
-static int smp_cpu_restart_nolock(uint16_t addr, struct psw *psw)
+static int smp_cpu_restart_nolock(uint16_t idx, struct psw *psw)
 {
 	int rc;
-	struct cpu *cpu = smp_cpu_from_addr(addr);
 
-	if (!cpu)
-		return -1;
+	check_idx(idx);
 	if (psw) {
-		cpu->lowcore->restart_new_psw.mask = psw->mask;
-		cpu->lowcore->restart_new_psw.addr = psw->addr;
+		cpus[idx].lowcore->restart_new_psw.mask = psw->mask;
+		cpus[idx].lowcore->restart_new_psw.addr = psw->addr;
 	}
 	/*
 	 * Stop the cpu, so we don't have a race between a running cpu
 	 * and the restart in the test that checks if the cpu is
 	 * running after the restart.
 	 */
-	smp_cpu_stop_nolock(addr, false);
-	rc = sigp(addr, SIGP_RESTART, 0, NULL);
+	smp_cpu_stop_nolock(idx, false);
+	rc = sigp(cpus[idx].addr, SIGP_RESTART, 0, NULL);
 	if (rc)
 		return rc;
 	/*
 	 * The order has been accepted, but the actual restart may not
 	 * have been performed yet, so wait until the cpu is running.
 	 */
-	while (smp_cpu_stopped(addr))
+	while (smp_cpu_stopped(idx))
 		mb();
-	cpu->active = true;
+	cpus[idx].active = true;
 	return 0;
 }
 
-int smp_cpu_restart(uint16_t addr)
+int smp_cpu_restart(uint16_t idx)
 {
 	int rc;
 
 	spin_lock(&lock);
-	rc = smp_cpu_restart_nolock(addr, NULL);
+	rc = smp_cpu_restart_nolock(idx, NULL);
 	spin_unlock(&lock);
 	return rc;
 }
 
-int smp_cpu_start(uint16_t addr, struct psw psw)
+int smp_cpu_start(uint16_t idx, struct psw psw)
 {
 	int rc;
 
 	spin_lock(&lock);
-	rc = smp_cpu_restart_nolock(addr, &psw);
+	rc = smp_cpu_restart_nolock(idx, &psw);
 	spin_unlock(&lock);
 	return rc;
 }
 
-int smp_cpu_destroy(uint16_t addr)
+int smp_cpu_destroy(uint16_t idx)
 {
-	struct cpu *cpu;
 	int rc;
 
 	spin_lock(&lock);
-	rc = smp_cpu_stop_nolock(addr, false);
+	rc = smp_cpu_stop_nolock(idx, false);
 	if (!rc) {
-		cpu = smp_cpu_from_addr(addr);
-		free_pages(cpu->lowcore);
-		free_pages(cpu->stack);
-		cpu->lowcore = (void *)-1UL;
-		cpu->stack = (void *)-1UL;
+		free_pages(cpus[idx].lowcore);
+		free_pages(cpus[idx].stack);
+		cpus[idx].lowcore = (void *)-1UL;
+		cpus[idx].stack = (void *)-1UL;
 	}
 	spin_unlock(&lock);
 	return rc;
 }
 
-int smp_cpu_setup(uint16_t addr, struct psw psw)
+static int smp_cpu_setup_nolock(uint16_t idx, struct psw psw)
 {
 	struct lowcore *lc;
-	struct cpu *cpu;
-	int rc = -1;
-
-	spin_lock(&lock);
-
-	if (!cpus)
-		goto out;
 
-	cpu = smp_cpu_from_addr(addr);
-
-	if (!cpu || cpu->active)
-		goto out;
+	if (cpus[idx].active)
+		return -1;
 
-	sigp_retry(cpu->addr, SIGP_INITIAL_CPU_RESET, 0, NULL);
+	sigp_retry(cpus[idx].addr, SIGP_INITIAL_CPU_RESET, 0, NULL);
 
 	lc = alloc_pages_flags(1, AREA_DMA31);
-	cpu->lowcore = lc;
-	memset(lc, 0, PAGE_SIZE * 2);
-	sigp_retry(cpu->addr, SIGP_SET_PREFIX, (unsigned long )lc, NULL);
+	cpus[idx].lowcore = lc;
+	sigp_retry(cpus[idx].addr, SIGP_SET_PREFIX, (unsigned long )lc, NULL);
 
 	/* Copy all exception psws. */
 	memcpy(lc, cpus[0].lowcore, 512);
 
 	/* Setup stack */
-	cpu->stack = (uint64_t *)alloc_pages(2);
+	cpus[idx].stack = (uint64_t *)alloc_pages(2);
 
 	/* Start without DAT and any other mask bits. */
-	cpu->lowcore->sw_int_psw.mask = psw.mask;
-	cpu->lowcore->sw_int_psw.addr = psw.addr;
-	cpu->lowcore->sw_int_grs[14] = psw.addr;
-	cpu->lowcore->sw_int_grs[15] = (uint64_t)cpu->stack + (PAGE_SIZE * 4);
+	lc->sw_int_psw.mask = psw.mask;
+	lc->sw_int_psw.addr = psw.addr;
+	lc->sw_int_grs[14] = psw.addr;
+	lc->sw_int_grs[15] = (uint64_t)cpus[idx].stack + (PAGE_SIZE * 4);
 	lc->restart_new_psw.mask = PSW_MASK_64;
 	lc->restart_new_psw.addr = (uint64_t)smp_cpu_setup_state;
 	lc->sw_int_crs[0] = BIT_ULL(CTL0_AFP);
 
 	/* Start processing */
-	smp_cpu_restart_nolock(addr, NULL);
+	smp_cpu_restart_nolock(idx, NULL);
 	/* Wait until the cpu has finished setup and started the provided psw */
 	while (lc->restart_new_psw.addr != psw.addr)
 		mb();
-	rc = 0;
-out:
+
+	return 0;
+}
+
+int smp_cpu_setup(uint16_t idx, struct psw psw)
+{
+	int rc = -1;
+
+	spin_lock(&lock);
+	if (cpus) {
+		check_idx(idx);
+		rc = smp_cpu_setup_nolock(idx, psw);
+	}
 	spin_unlock(&lock);
 	return rc;
 }
