[RFC PATCH 2/2] powerpc/powernv: implement NMI IPIs with OPAL_SIGNAL_SYSTEM_RESET
Nicholas Piggin
npiggin at gmail.com
Thu Sep 14 21:26:03 AEST 2017
On Wed, 13 Sep 2017 02:05:53 +1000
Nicholas Piggin <npiggin at gmail.com> wrote:
> There are two complications. The first is that sreset from stop states
> come in with SRR1 set to do a powersave wakeup, with an sreset reason
> encoded.
>
> The second is that threads on the same core can't be signalled directly
> so we must designate a bounce CPU to reflect the IPI back.
This is a revised patch with only DD2 enablement. DD2 allows threads on
the same core to be IPIed. It's much simpler, and most of the code is
fixing the watchdog and preventing it from triggering from xmon (which
will be split into other patches of course).
It's probably a better starting point to get this working and merged
first, then revisiting bouncing.
---
arch/powerpc/include/asm/opal-api.h | 1 +
arch/powerpc/include/asm/opal.h | 2 ++
arch/powerpc/kernel/irq.c | 20 ++++++++++++++++++
arch/powerpc/kernel/watchdog.c | 29 +++++++++++++++-----------
arch/powerpc/platforms/powernv/opal-wrappers.S | 1 +
arch/powerpc/platforms/powernv/powernv.h | 1 +
arch/powerpc/platforms/powernv/setup.c | 3 +++
arch/powerpc/platforms/powernv/smp.c | 24 +++++++++++++++++++++
arch/powerpc/xmon/xmon.c | 17 +++++++++++----
9 files changed, 82 insertions(+), 16 deletions(-)
diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h
index 450a60b81d2a..9d191ebea706 100644
--- a/arch/powerpc/include/asm/opal-api.h
+++ b/arch/powerpc/include/asm/opal-api.h
@@ -188,6 +188,7 @@
#define OPAL_XIVE_DUMP 142
#define OPAL_XIVE_RESERVED3 143
#define OPAL_XIVE_RESERVED4 144
+#define OPAL_SIGNAL_SYSTEM_RESET 145
#define OPAL_NPU_INIT_CONTEXT 146
#define OPAL_NPU_DESTROY_CONTEXT 147
#define OPAL_NPU_MAP_LPAR 148
diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 726c23304a57..7d7613c49f2b 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -281,6 +281,8 @@ int opal_get_power_shift_ratio(u32 handle, int token, u32 *psr);
int opal_set_power_shift_ratio(u32 handle, int token, u32 psr);
int opal_sensor_group_clear(u32 group_hndl, int token);
+int64_t opal_signal_system_reset(int32_t cpu);
+
/* Internal functions */
extern int early_init_dt_scan_opal(unsigned long node, const char *uname,
int depth, void *data);
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 4e65bf82f5e0..8ffebb9437e5 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -407,11 +407,31 @@ static const u8 srr1_to_lazyirq[0x10] = {
PACA_IRQ_HMI,
0, 0, 0, 0, 0 };
+static noinline void replay_system_reset(void)
+{
+ struct pt_regs regs;
+
+ ppc_save_regs(®s);
+
+ get_paca()->in_nmi = 1;
+ system_reset_exception(®s);
+ get_paca()->in_nmi = 0;
+}
+
void irq_set_pending_from_srr1(unsigned long srr1)
{
unsigned int idx = (srr1 & SRR1_WAKEMASK_P8) >> 18;
/*
+ * 0100b SRR1 reason is system reset. Take it now,
+ * which is immediately after registers are restored
+ * from idle. It's an NMI, so interrupts needn't be
+ * re-enabled.
+ */
+ if (unlikely(idx == 4))
+ replay_system_reset();
+
+ /*
* The 0 index (SRR1[42:45]=b0000) must always evaluate to 0,
* so this can be called unconditionally with srr1 wake reason.
*/
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 2f6eadd9408d..1fb9379dc683 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -97,8 +97,7 @@ static void wd_lockup_ipi(struct pt_regs *regs)
else
dump_stack();
- if (hardlockup_panic)
- nmi_panic(regs, "Hard LOCKUP");
+ /* Do not panic from here because that can recurse into NMI IPI layer */
}
static void set_cpumask_stuck(const struct cpumask *cpumask, u64 tb)
@@ -134,15 +133,18 @@ static void watchdog_smp_panic(int cpu, u64 tb)
pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
cpu, cpumask_pr_args(&wd_smp_cpus_pending));
- /*
- * Try to trigger the stuck CPUs.
- */
- for_each_cpu(c, &wd_smp_cpus_pending) {
- if (c == cpu)
- continue;
- smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
+ if (!sysctl_hardlockup_all_cpu_backtrace) {
+ /*
+ * Try to trigger the stuck CPUs, unless we are going to
+ * get a backtrace on all of them anyway.
+ */
+ for_each_cpu(c, &wd_smp_cpus_pending) {
+ if (c == cpu)
+ continue;
+ smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
+ }
+ smp_flush_nmi_ipi(1000000);
}
- smp_flush_nmi_ipi(1000000);
/* Take the stuck CPUs out of the watch group */
set_cpumask_stuck(&wd_smp_cpus_pending, tb);
@@ -275,9 +277,12 @@ void arch_touch_nmi_watchdog(void)
{
unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000;
int cpu = smp_processor_id();
+ u64 tb = get_tb();
- if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks)
- watchdog_timer_interrupt(cpu);
+ if (tb - per_cpu(wd_timer_tb, cpu) >= ticks) {
+ per_cpu(wd_timer_tb, cpu) = tb;
+ wd_smp_clear_cpu_pending(cpu, tb);
+ }
}
EXPORT_SYMBOL(arch_touch_nmi_watchdog);
diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
index 8c1ede2d3f7e..37cd170201a2 100644
--- a/arch/powerpc/platforms/powernv/opal-wrappers.S
+++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
@@ -307,6 +307,7 @@ OPAL_CALL(opal_xive_get_vp_info, OPAL_XIVE_GET_VP_INFO);
OPAL_CALL(opal_xive_set_vp_info, OPAL_XIVE_SET_VP_INFO);
OPAL_CALL(opal_xive_sync, OPAL_XIVE_SYNC);
OPAL_CALL(opal_xive_dump, OPAL_XIVE_DUMP);
+OPAL_CALL(opal_signal_system_reset, OPAL_SIGNAL_SYSTEM_RESET);
OPAL_CALL(opal_npu_init_context, OPAL_NPU_INIT_CONTEXT);
OPAL_CALL(opal_npu_destroy_context, OPAL_NPU_DESTROY_CONTEXT);
OPAL_CALL(opal_npu_map_lpar, OPAL_NPU_MAP_LPAR);
diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
index a159d48573d7..49add2037e0d 100644
--- a/arch/powerpc/platforms/powernv/powernv.h
+++ b/arch/powerpc/platforms/powernv/powernv.h
@@ -3,6 +3,7 @@
#ifdef CONFIG_SMP
extern void pnv_smp_init(void);
+extern int pnv_system_reset_exception(struct pt_regs *regs);
#else
static inline void pnv_smp_init(void) { }
#endif
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 897aa1400eb8..4fdaa1d7c4cd 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -282,6 +282,9 @@ static void __init pnv_setup_machdep_opal(void)
ppc_md.restart = pnv_restart;
pm_power_off = pnv_power_off;
ppc_md.halt = pnv_halt;
+#ifdef CONFIG_SMP
+ ppc_md.system_reset_exception = pnv_system_reset_exception;
+#endif
ppc_md.machine_check_exception = opal_machine_check;
ppc_md.mce_check_early_recovery = opal_mce_check_early_recovery;
ppc_md.hmi_exception_early = opal_hmi_exception_early;
diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
index c17f81e433f7..83343832e07e 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c
@@ -290,6 +290,28 @@ static void __init pnv_smp_probe(void)
}
}
+int pnv_system_reset_exception(struct pt_regs *regs)
+{
+ if (smp_handle_nmi_ipi(regs))
+ return 1;
+ return 0;
+}
+
+static int pnv_cause_nmi_ipi(int cpu)
+{
+ int64_t rc;
+
+ rc = opal_signal_system_reset(cpu);
+ if (rc == OPAL_SUCCESS)
+ return 1;
+
+ /*
+ * Don't cope with OPAL_PARTIAL yet (just punt to regular IPI)
+ */
+
+ return 0;
+}
+
static struct smp_ops_t pnv_smp_ops = {
.message_pass = NULL, /* Use smp_muxed_ipi_message_pass */
.cause_ipi = NULL, /* Filled at runtime by pnv_smp_probe() */
@@ -308,6 +330,8 @@ static struct smp_ops_t pnv_smp_ops = {
/* This is called very early during platform setup_arch */
void __init pnv_smp_init(void)
{
+ if (opal_check_token(OPAL_SIGNAL_SYSTEM_RESET))
+ pnv_smp_ops.cause_nmi_ipi = pnv_cause_nmi_ipi;
smp_ops = &pnv_smp_ops;
#ifdef CONFIG_HOTPLUG_CPU
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 33351c6704b1..d9a12102b111 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -530,14 +530,19 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
waiting:
secondary = 1;
+ spin_begin();
while (secondary && !xmon_gate) {
if (in_xmon == 0) {
- if (fromipi)
+ if (fromipi) {
+ spin_end();
goto leave;
+ }
secondary = test_and_set_bit(0, &in_xmon);
}
- barrier();
+ spin_cpu_relax();
+ touch_nmi_watchdog();
}
+ spin_end();
if (!secondary && !xmon_gate) {
/* we are the first cpu to come in */
@@ -568,21 +573,25 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
mb();
xmon_gate = 1;
barrier();
+ touch_nmi_watchdog();
}
cmdloop:
while (in_xmon) {
if (secondary) {
+ spin_begin();
if (cpu == xmon_owner) {
if (!test_and_set_bit(0, &xmon_taken)) {
secondary = 0;
+ spin_end();
continue;
}
/* missed it */
while (cpu == xmon_owner)
- barrier();
+ spin_cpu_relax();
}
- barrier();
+ spin_cpu_relax();
+ touch_nmi_watchdog();
} else {
cmd = cmds(regs);
if (cmd != 0) {
--
2.13.3
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