s390 update with bug fixes for 5.0-rc4

- Do not claim to run under z/VM if the hypervisor can not be identified
 
  - Fix crashes due to outdated ASCEs in CR1
 
  - Avoid a deadlock in regard to CPU hotplug
 
  - Really fix the vdso mapping issue for compat tasks
 
  - Avoid crash on restart due to an incorrect stack address
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Merge tag 's390-5.0-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

Pull s390 fixes from Martin Schwidefsky:

 - Do not claim to run under z/VM if the hypervisor can not be
   identified

 - Fix crashes due to outdated ASCEs in CR1

 - Avoid a deadlock in regard to CPU hotplug

 - Really fix the vdso mapping issue for compat tasks

 - Avoid crash on restart due to an incorrect stack address

* tag 's390-5.0-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/smp: Fix calling smp_call_ipl_cpu() from ipl CPU
  s390/vdso: correct vdso mapping for compat tasks
  s390/smp: fix CPU hotplug deadlock with CPU rescan
  s390/mm: always force a load of the primary ASCE on context switch
  s390/early: improve machine detection

arch/s390/include/asm/mmu_context.h

@@ -25,7 +25,7 @@ static inline int init_new_context(struct task_struct *tsk,
 	atomic_set(&mm->context.flush_count, 0);
 	mm->context.gmap_asce = 0;
 	mm->context.flush_mm = 0;
-	mm->context.compat_mm = 0;
+	mm->context.compat_mm = test_thread_flag(TIF_31BIT);
 #ifdef CONFIG_PGSTE
 	mm->context.alloc_pgste = page_table_allocate_pgste ||
 		test_thread_flag(TIF_PGSTE) ||
@@ -90,8 +90,6 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 {
 	int cpu = smp_processor_id();
 
-	if (prev == next)
-		return;
 	S390_lowcore.user_asce = next->context.asce;
 	cpumask_set_cpu(cpu, &next->context.cpu_attach_mask);
 	/* Clear previous user-ASCE from CR1 and CR7 */
@@ -103,6 +101,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 		__ctl_load(S390_lowcore.vdso_asce, 7, 7);
 		clear_cpu_flag(CIF_ASCE_SECONDARY);
 	}
+	if (prev != next)
 		cpumask_clear_cpu(cpu, &prev->context.cpu_attach_mask);
 }
 

arch/s390/kernel/early.c

@@ -63,10 +63,10 @@ static noinline __init void detect_machine_type(void)
 	if (stsi(vmms, 3, 2, 2) || !vmms->count)
 		return;
 
-	/* Running under KVM? If not we assume z/VM */
+	/* Detect known hypervisors */
 	if (!memcmp(vmms->vm[0].cpi, "\xd2\xe5\xd4", 3))
 		S390_lowcore.machine_flags |= MACHINE_FLAG_KVM;
-	else
+	else if (!memcmp(vmms->vm[0].cpi, "\xa9\x61\xe5\xd4", 4))
 		S390_lowcore.machine_flags |= MACHINE_FLAG_VM;
 }
 

arch/s390/kernel/setup.c

@@ -1006,6 +1006,8 @@ void __init setup_arch(char **cmdline_p)
 		pr_info("Linux is running under KVM in 64-bit mode\n");
 	else if (MACHINE_IS_LPAR)
 		pr_info("Linux is running natively in 64-bit mode\n");
+	else
+		pr_info("Linux is running as a guest in 64-bit mode\n");
 
 	/* Have one command line that is parsed and saved in /proc/cmdline */
 	/* boot_command_line has been already set up in early.c */

arch/s390/kernel/smp.c

@@ -381,8 +381,13 @@ void smp_call_online_cpu(void (*func)(void *), void *data)
  */
 void smp_call_ipl_cpu(void (*func)(void *), void *data)
 {
+	struct lowcore *lc = pcpu_devices->lowcore;
+
+	if (pcpu_devices[0].address == stap())
+		lc = &S390_lowcore;
+
 	pcpu_delegate(&pcpu_devices[0], func, data,
-		      pcpu_devices->lowcore->nodat_stack);
+		      lc->nodat_stack);
 }
 
 int smp_find_processor_id(u16 address)
@@ -1166,7 +1171,11 @@ static ssize_t __ref rescan_store(struct device *dev,
 {
 	int rc;
 
+	rc = lock_device_hotplug_sysfs();
+	if (rc)
+		return rc;
 	rc = smp_rescan_cpus();
+	unlock_device_hotplug();
 	return rc ? rc : count;
 }
 static DEVICE_ATTR_WO(rescan);

arch/s390/kernel/vdso.c

@@ -224,10 +224,9 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 
 	vdso_pages = vdso64_pages;
 #ifdef CONFIG_COMPAT
-	if (is_compat_task()) {
+	mm->context.compat_mm = is_compat_task();
+	if (mm->context.compat_mm)
 		vdso_pages = vdso32_pages;
-		mm->context.compat_mm = 1;
-	}
 #endif
 	/*
 	 * vDSO has a problem and was disabled, just don't "enable" it for

drivers/s390/char/sclp_config.c

@@ -60,7 +60,9 @@ static void sclp_cpu_capability_notify(struct work_struct *work)
 
 static void __ref sclp_cpu_change_notify(struct work_struct *work)
 {
+	lock_device_hotplug();
 	smp_rescan_cpus();
+	unlock_device_hotplug();
 }
 
 static void sclp_conf_receiver_fn(struct evbuf_header *evbuf)