[PATCH V5 2/2] riscv: kexec: Fixup crash_smp_send_stop without multi cores

From: guoren
Date: Thu Oct 20 2022 - 10:17:07 EST

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From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>

Current crash_smp_send_stop is the same as the generic one in
kernel/panic and misses crash_save_cpu in percpu. This patch is inspired
by 78fd584cdec0 ("arm64: kdump: implement machine_crash_shutdown()")
and adds the same mechanism for riscv.

Before this patch, test result:
crash> help -r
CPU 0: [OFFLINE]

CPU 1:
epc : ffffffff80009ff0 ra : ffffffff800b789a sp : ff2000001098bb40
gp : ffffffff815fca60 tp : ff60000004680000 t0 : 6666666666663c5b
t1 : 0000000000000000 t2 : 666666666666663c s0 : ff2000001098bc90
s1 : ffffffff81600798 a0 : ff2000001098bb48 a1 : 0000000000000000
a2 : 0000000000000000 a3 : 0000000000000001 a4 : 0000000000000000
a5 : ff60000004690800 a6 : 0000000000000000 a7 : 0000000000000000
s2 : ff2000001098bb48 s3 : ffffffff81093ec8 s4 : ffffffff816004ac
s5 : 0000000000000000 s6 : 0000000000000007 s7 : ffffffff80e7f720
s8 : 00fffffffffff3f0 s9 : 0000000000000007 s10: 00aaaaaaaab98700
s11: 0000000000000001 t3 : ffffffff819a8097 t4 : ffffffff819a8097
t5 : ffffffff819a8098 t6 : ff2000001098b9a8

CPU 2: [OFFLINE]

CPU 3: [OFFLINE]

After this patch, test result:
crash> help -r
CPU 0:
epc : ffffffff80003f34 ra : ffffffff808caa7c sp : ffffffff81403eb0
gp : ffffffff815fcb48 tp : ffffffff81413400 t0 : 0000000000000000
t1 : 0000000000000000 t2 : 0000000000000000 s0 : ffffffff81403ec0
s1 : 0000000000000000 a0 : 0000000000000000 a1 : 0000000000000000
a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000
s2 : ffffffff816001c8 s3 : ffffffff81600370 s4 : ffffffff80c32e18
s5 : ffffffff819d3018 s6 : ffffffff810e2110 s7 : 0000000000000000
s8 : 0000000000000000 s9 : 0000000080039eac s10: 0000000000000000
s11: 0000000000000000 t3 : 0000000000000000 t4 : 0000000000000000
t5 : 0000000000000000 t6 : 0000000000000000

CPU 1:
epc : ffffffff80003f34 ra : ffffffff808caa7c sp : ff2000000068bf30
gp : ffffffff815fcb48 tp : ff6000000240d400 t0 : 0000000000000000
t1 : 0000000000000000 t2 : 0000000000000000 s0 : ff2000000068bf40
s1 : 0000000000000001 a0 : 0000000000000000 a1 : 0000000000000000
a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000
s2 : ffffffff816001c8 s3 : ffffffff81600370 s4 : ffffffff80c32e18
s5 : ffffffff819d3018 s6 : ffffffff810e2110 s7 : 0000000000000000
s8 : 0000000000000000 s9 : 0000000080039ea8 s10: 0000000000000000
s11: 0000000000000000 t3 : 0000000000000000 t4 : 0000000000000000
t5 : 0000000000000000 t6 : 0000000000000000

CPU 2:
epc : ffffffff80003f34 ra : ffffffff808caa7c sp : ff20000000693f30
gp : ffffffff815fcb48 tp : ff6000000240e900 t0 : 0000000000000000
t1 : 0000000000000000 t2 : 0000000000000000 s0 : ff20000000693f40
s1 : 0000000000000002 a0 : 0000000000000000 a1 : 0000000000000000
a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000
s2 : ffffffff816001c8 s3 : ffffffff81600370 s4 : ffffffff80c32e18
s5 : ffffffff819d3018 s6 : ffffffff810e2110 s7 : 0000000000000000
s8 : 0000000000000000 s9 : 0000000080039eb0 s10: 0000000000000000
s11: 0000000000000000 t3 : 0000000000000000 t4 : 0000000000000000
t5 : 0000000000000000 t6 : 0000000000000000

CPU 3:
epc : ffffffff8000a1e4 ra : ffffffff800b7bba sp : ff200000109bbb40
gp : ffffffff815fcb48 tp : ff6000000373aa00 t0 : 6666666666663c5b
t1 : 0000000000000000 t2 : 666666666666663c s0 : ff200000109bbc90
s1 : ffffffff816007a0 a0 : ff200000109bbb48 a1 : 0000000000000000
a2 : 0000000000000000 a3 : 0000000000000001 a4 : 0000000000000000
a5 : ff60000002c61c00 a6 : 0000000000000000 a7 : 0000000000000000
s2 : ff200000109bbb48 s3 : ffffffff810941a8 s4 : ffffffff816004b4
s5 : 0000000000000000 s6 : 0000000000000007 s7 : ffffffff80e7f7a0
s8 : 00fffffffffff3f0 s9 : 0000000000000007 s10: 00aaaaaaaab98700
s11: 0000000000000001 t3 : ffffffff819a8097 t4 : ffffffff819a8097
t5 : ffffffff819a8098 t6 : ff200000109bb9a8

Fixes: ad943893d5f1 ("RISC-V: Fixup schedule out issue in machine_crash_shutdown()")
Reviewed-by: Xianting Tian <xianting.tian@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
Cc: Nick Kossifidis <mick@xxxxxxxxxxxx>
---
arch/riscv/include/asm/smp.h | 3 +
arch/riscv/kernel/machine_kexec.c | 21 ++-----
arch/riscv/kernel/smp.c | 97 ++++++++++++++++++++++++++++++-
3 files changed, 103 insertions(+), 18 deletions(-)

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index d3443be7eedc..3831b638ecab 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -50,6 +50,9 @@ void riscv_set_ipi_ops(const struct riscv_ipi_ops *ops);
/* Clear IPI for current CPU */
void riscv_clear_ipi(void);

+/* Check other CPUs stop or not */
+bool smp_crash_stop_failed(void);
+
/* Secondary hart entry */
asmlinkage void smp_callin(void);

diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
index db41c676e5a2..2d139b724bc8 100644
--- a/arch/riscv/kernel/machine_kexec.c
+++ b/arch/riscv/kernel/machine_kexec.c
@@ -140,22 +140,6 @@ void machine_shutdown(void)
#endif
}

-/* Override the weak function in kernel/panic.c */
-void crash_smp_send_stop(void)
-{
- static int cpus_stopped;
-
- /*
- * This function can be called twice in panic path, but obviously
- * we execute this only once.
- */
- if (cpus_stopped)
- return;
-
- smp_send_stop();
- cpus_stopped = 1;
-}
-
static void machine_kexec_mask_interrupts(void)
{
unsigned int i;
@@ -230,6 +214,11 @@ machine_kexec(struct kimage *image)
void *control_code_buffer = page_address(image->control_code_page);
riscv_kexec_method kexec_method = NULL;

+#ifdef CONFIG_SMP
+ WARN(smp_crash_stop_failed(),
+ "Some CPUs may be stale, kdump will be unreliable.\n");
+#endif
+
if (image->type != KEXEC_TYPE_CRASH)
kexec_method = control_code_buffer;
else
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 760a64518c58..8c3b59f1f9b8 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -12,6 +12,7 @@
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/module.h>
+#include <linux/kexec.h>
#include <linux/profile.h>
#include <linux/smp.h>
#include <linux/sched.h>
@@ -22,11 +23,13 @@
#include <asm/sbi.h>
#include <asm/tlbflush.h>
#include <asm/cacheflush.h>
+#include <asm/cpu_ops.h>

enum ipi_message_type {
IPI_RESCHEDULE,
IPI_CALL_FUNC,
IPI_CPU_STOP,
+ IPI_CPU_CRASH_STOP,
IPI_IRQ_WORK,
IPI_TIMER,
IPI_MAX
@@ -71,6 +74,32 @@ static void ipi_stop(void)
wait_for_interrupt();
}

+#ifdef CONFIG_KEXEC_CORE
+static atomic_t waiting_for_crash_ipi = ATOMIC_INIT(0);
+
+static inline void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
+{
+ crash_save_cpu(regs, cpu);
+
+ atomic_dec(&waiting_for_crash_ipi);
+
+ local_irq_disable();
+
+#ifdef CONFIG_HOTPLUG_CPU
+ if (cpu_has_hotplug(cpu))
+ cpu_ops[cpu]->cpu_stop();
+#endif
+
+ for(;;)
+ wait_for_interrupt();
+}
+#else
+static inline void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
+{
+ unreachable();
+}
+#endif
+
static const struct riscv_ipi_ops *ipi_ops __ro_after_init;

void riscv_set_ipi_ops(const struct riscv_ipi_ops *ops)
@@ -124,8 +153,9 @@ void arch_irq_work_raise(void)

void handle_IPI(struct pt_regs *regs)
{
- unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
- unsigned long *stats = ipi_data[smp_processor_id()].stats;
+ unsigned int cpu = smp_processor_id();
+ unsigned long *pending_ipis = &ipi_data[cpu].bits;
+ unsigned long *stats = ipi_data[cpu].stats;

riscv_clear_ipi();

@@ -154,6 +184,10 @@ void handle_IPI(struct pt_regs *regs)
ipi_stop();
}

+ if (ops & (1 << IPI_CPU_CRASH_STOP)) {
+ ipi_cpu_crash_stop(cpu, get_irq_regs());
+ }
+
if (ops & (1 << IPI_IRQ_WORK)) {
stats[IPI_IRQ_WORK]++;
irq_work_run();
@@ -176,6 +210,7 @@ static const char * const ipi_names[] = {
[IPI_RESCHEDULE] = "Rescheduling interrupts",
[IPI_CALL_FUNC] = "Function call interrupts",
[IPI_CPU_STOP] = "CPU stop interrupts",
+ [IPI_CPU_CRASH_STOP] = "CPU stop (for crash dump) interrupts",
[IPI_IRQ_WORK] = "IRQ work interrupts",
[IPI_TIMER] = "Timer broadcast interrupts",
};
@@ -235,6 +270,64 @@ void smp_send_stop(void)
cpumask_pr_args(cpu_online_mask));
}

+#ifdef CONFIG_KEXEC_CORE
+/*
+ * The number of CPUs online, not counting this CPU (which may not be
+ * fully online and so not counted in num_online_cpus()).
+ */
+static inline unsigned int num_other_online_cpus(void)
+{
+ unsigned int this_cpu_online = cpu_online(smp_processor_id());
+
+ return num_online_cpus() - this_cpu_online;
+}
+
+void crash_smp_send_stop(void)
+{
+ static int cpus_stopped;
+ cpumask_t mask;
+ unsigned long timeout;
+
+ /*
+ * This function can be called twice in panic path, but obviously
+ * we execute this only once.
+ */
+ if (cpus_stopped)
+ return;
+
+ cpus_stopped = 1;
+
+ /*
+ * If this cpu is the only one alive at this point in time, online or
+ * not, there are no stop messages to be sent around, so just back out.
+ */
+ if (num_other_online_cpus() == 0)
+ return;
+
+ cpumask_copy(&mask, cpu_online_mask);
+ cpumask_clear_cpu(smp_processor_id(), &mask);
+
+ atomic_set(&waiting_for_crash_ipi, num_other_online_cpus());
+
+ pr_crit("SMP: stopping secondary CPUs\n");
+ send_ipi_mask(&mask, IPI_CPU_CRASH_STOP);
+
+ /* Wait up to one second for other CPUs to stop */
+ timeout = USEC_PER_SEC;
+ while ((atomic_read(&waiting_for_crash_ipi) > 0) && timeout--)
+ udelay(1);
+
+ if (atomic_read(&waiting_for_crash_ipi) > 0)
+ pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",
+ cpumask_pr_args(&mask));
+}
+
+bool smp_crash_stop_failed(void)
+{
+ return (atomic_read(&waiting_for_crash_ipi) > 0);
+}
+#endif
+
void smp_send_reschedule(int cpu)
{
send_ipi_single(cpu, IPI_RESCHEDULE);
--
2.36.1

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Previous message: guoren: "[PATCH V5 1/2] riscv: kexec: Fixup irq controller broken in kexec crash path"
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