[S390] smp: always reboot on cpu 0

Always reboot on logical cpu 0. This makes sure that the IPL cpu is
always the same and usually avoids strange numbering schemes between
physical and logical cpus.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 35 insertions, 1 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 384a6846a65e..b39f596d71bd 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -90,6 +90,39 @@ static int cpu_stopped(int cpu)
         return 0;
 }
 
+void smp_switch_to_ipl_cpu(void (*func)(void *), void *data)
+{
+        struct _lowcore *lc, *current_lc;
+        struct stack_frame *sf;
+        struct pt_regs *regs;
+        unsigned long sp;
+
+        if (smp_processor_id() == 0)
+                func(data);
+        __load_psw_mask(PSW_BASE_BITS | PSW_DEFAULT_KEY);
+        /* Disable lowcore protection */
+        __ctl_clear_bit(0, 28);
+        current_lc = lowcore_ptr[smp_processor_id()];
+        lc = lowcore_ptr[0];
+        if (!lc)
+                lc = current_lc;
+        lc->restart_psw.mask = PSW_BASE_BITS | PSW_DEFAULT_KEY;
+        lc->restart_psw.addr = PSW_ADDR_AMODE | (unsigned long) smp_restart_cpu;
+        if (!cpu_online(0))
+                smp_switch_to_cpu(func, data, 0, stap(), __cpu_logical_map[0]);
+        while (signal_processor(0, sigp_stop_and_store_status) == sigp_busy)
+                cpu_relax();
+        sp = lc->panic_stack;
+        sp -= sizeof(struct pt_regs);
+        regs = (struct pt_regs *) sp;
+        memcpy(&regs->gprs, &current_lc->gpregs_save_area, sizeof(regs->gprs));
+        memcpy(&regs->psw, &current_lc->st_status_fixed_logout, sizeof(psw_t));
+        sp -= STACK_FRAME_OVERHEAD;
+        sf = (struct stack_frame *) sp;
+        sf->back_chain = regs->gprs[15];
+        smp_switch_to_cpu(func, data, sp, stap(), __cpu_logical_map[0]);
+}
+
 void smp_send_stop(void)
 {
         int cpu, rc;
@@ -752,7 +785,8 @@ static ssize_t cpu_configure_store(struct sys_device *dev,
         get_online_cpus();
         mutex_lock(&smp_cpu_state_mutex);
         rc = -EBUSY;
-        if (cpu_online(cpu))
+        /* disallow configuration changes of online cpus and cpu 0 */
+        if (cpu_online(cpu) || cpu == 0)
                 goto out;
         rc = 0;
         switch (val) {