s390/smp: enable DAT before CPU restart callback is called

The restart interrupt is triggered whenever a secondary CPU is
brought online, a remote function call dispatched from another
CPU or a manual PSW restart is initiated and causes the system
to kdump. The handling routine is always called with DAT turned
off. It then initializes the stack frame and invokes a callback.

The existing callbacks handle DAT as follows:

  * __do_restart() and __machine_kexec() turn in on upon entry;
  * __ipl_run(), __reipl_run() and __dump_run() do not turn it
    right away, but all of them call diag308() - which turns DAT
    on, but only if kasan is enabled;

In addition to the described complexity all callbacks (and the
functions they call) should avoid kasan instrumentation while
DAT is off.

This update enables DAT in the assembler restart handler and
relieves any callbacks (which are mostly C functions) from
dealing with DAT altogether.

There are four types of CPU restart that initialize control
registers in different ways:

  1. Start of secondary CPU on boot - control registers are
     inherited from the IPL CPU;
  2. Restart of online CPU - control registers of the CPU being
     restarted are kept;
  3. Hotplug of offline CPU - control registers are inherited
     from the starting CPU;
  4. Start of offline CPU triggered by manual PSW restart -
     the control registers are read from the absolute lowcore
     and contain the boot time IPL CPU values updated with all
     follow-up calls of smp_ctl_set_bit() and smp_ctl_clear_bit()
     routines;

In first three cases contents of the control registers is the
most recent. In the latter case control registers are good
enough to facilitate successful completion of kdump operation.

Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 22 insertions, 9 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 09dc13a8d390..e4190bc8cb36 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -252,6 +252,7 @@ static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)
 	cpumask_set_cpu(cpu, &init_mm.context.cpu_attach_mask);
 	cpumask_set_cpu(cpu, mm_cpumask(&init_mm));
 	lc->cpu_nr = cpu;
+	lc->restart_flags = RESTART_FLAG_CTLREGS;
 	lc->spinlock_lockval = arch_spin_lockval(cpu);
 	lc->spinlock_index = 0;
 	lc->percpu_offset = __per_cpu_offset[cpu];
@@ -297,7 +298,7 @@ static void pcpu_start_fn(struct pcpu *pcpu, void (*func)(void *), void *data)
 	lc->restart_stack = lc->nodat_stack;
 	lc->restart_fn = (unsigned long) func;
 	lc->restart_data = (unsigned long) data;
-	lc->restart_source = -1UL;
+	lc->restart_source = -1U;
 	pcpu_sigp_retry(pcpu, SIGP_RESTART, 0);
 }
 
@@ -311,12 +312,12 @@ static void __pcpu_delegate(pcpu_delegate_fn *func, void *data)
 	func(data);	/* should not return */
 }
 
-static void __no_sanitize_address pcpu_delegate(struct pcpu *pcpu,
-						pcpu_delegate_fn *func,
-						void *data, unsigned long stack)
+static void pcpu_delegate(struct pcpu *pcpu,
+			  pcpu_delegate_fn *func,
+			  void *data, unsigned long stack)
 {
 	struct lowcore *lc = lowcore_ptr[pcpu - pcpu_devices];
-	unsigned long source_cpu = stap();
+	unsigned int source_cpu = stap();
 
 	__load_psw_mask(PSW_KERNEL_BITS | PSW_MASK_DAT);
 	if (pcpu->address == source_cpu) {
@@ -569,6 +570,9 @@ static void smp_ctl_bit_callback(void *info)
 	__ctl_load(cregs, 0, 15);
 }
 
+static DEFINE_SPINLOCK(ctl_lock);
+static unsigned long ctlreg;
+
 /*
  * Set a bit in a control register of all cpus
  */
@@ -576,6 +580,11 @@ void smp_ctl_set_bit(int cr, int bit)
 {
 	struct ec_creg_mask_parms parms = { 1UL << bit, -1UL, cr };
 
+	spin_lock(&ctl_lock);
+	memcpy_absolute(&ctlreg, &S390_lowcore.cregs_save_area[cr], sizeof(ctlreg));
+	__set_bit(bit, &ctlreg);
+	memcpy_absolute(&S390_lowcore.cregs_save_area[cr], &ctlreg, sizeof(ctlreg));
+	spin_unlock(&ctl_lock);
 	on_each_cpu(smp_ctl_bit_callback, &parms, 1);
 }
 EXPORT_SYMBOL(smp_ctl_set_bit);
@@ -587,6 +596,11 @@ void smp_ctl_clear_bit(int cr, int bit)
 {
 	struct ec_creg_mask_parms parms = { 0, ~(1UL << bit), cr };
 
+	spin_lock(&ctl_lock);
+	memcpy_absolute(&ctlreg, &S390_lowcore.cregs_save_area[cr], sizeof(ctlreg));
+	__clear_bit(bit, &ctlreg);
+	memcpy_absolute(&S390_lowcore.cregs_save_area[cr], &ctlreg, sizeof(ctlreg));
+	spin_unlock(&ctl_lock);
 	on_each_cpu(smp_ctl_bit_callback, &parms, 1);
 }
 EXPORT_SYMBOL(smp_ctl_clear_bit);
@@ -895,14 +909,13 @@ static void smp_init_secondary(void)
 /*
  *	Activate a secondary processor.
  */
-static void __no_sanitize_address smp_start_secondary(void *cpuvoid)
+static void smp_start_secondary(void *cpuvoid)
 {
 	S390_lowcore.restart_stack = (unsigned long) restart_stack;
 	S390_lowcore.restart_fn = (unsigned long) do_restart;
 	S390_lowcore.restart_data = 0;
-	S390_lowcore.restart_source = -1UL;
-	__ctl_load(S390_lowcore.cregs_save_area, 0, 15);
-	__load_psw_mask(PSW_KERNEL_BITS | PSW_MASK_DAT);
+	S390_lowcore.restart_source = -1U;
+	S390_lowcore.restart_flags = 0;
 	call_on_stack_noreturn(smp_init_secondary, S390_lowcore.kernel_stack);
 }