On 2023/7/5 16:59, Thomas Gleixner wrote:
On Mon, Jul 03 2023 at 11:44, Baokun Li wrote:
When I manually trigger panic in a qume x86 VM with
`echo c > /proc/sysrq-trigger`,
I find that the VM will probably reboot directly, but the
PANIC_TIMEOUT is 0.
This prevents us from exporting the vmcore via panic, and even if we succeed
in panic exporting the vmcore, the processes in the vmcore are mostly
stop_this_cpu(). By dichotomizing we found the patch that introduced the
behavior change
45e34c8af58f ("x86/smp: Put CPUs into INIT on shutdown if possible"),
Bah, I missed that this is used by crash too. So if this happens to be
invoked on an AP, i.e. not on CPU 0, then the INIT will reset the
machine. Fix below.
Thanks,
tglx
---
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ed2d51960a7d..e1aa2cd7734b 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1348,6 +1348,14 @@ bool smp_park_other_cpus_in_init(void)
if (apic->wakeup_secondary_cpu_64 || apic->wakeup_secondary_cpu)
return false;
+ /*
+ * If this is a crash stop which does not execute on the boot CPU,
+ * then this cannot use the INIT mechanism because INIT to the boot
+ * CPU will reset the machine.
+ */
+ if (this_cpu)
+ return false;
+
for_each_present_cpu(cpu) {
if (cpu == this_cpu)
continue;
This patch does fix the problem of rebooting at panic, but the exported
stack
stays at stop_this_cpu() like below, instead of showing what the
corresponding
process is doing as before.
PID: 681 TASK: ffff9ac2429d3080 CPU: 2 COMMAND: "fsstress"
#0 [ffffb00200184fd0] stop_this_cpu at ffffffff89a4ffd8
#1 [ffffb00200184fe8] __sysvec_reboot at ffffffff89a94213
#2 [ffffb00200184ff0] sysvec_reboot at ffffffff8aee7491
--- <IRQ stack> ---
RIP: 0000000000000010 RSP: 0000000000000018 RFLAGS: ffffb00200f8bd08
RAX: ffff9ac256fda9d8 RBX: 0000000009973a85 RCX: ffff9ac256fda078
RDX: ffff9ac24416e300 RSI: ffff9ac256fda9e0 RDI: ffffffffffffffff
RBP: ffff9ac2443a5f88 R8: 0000000000000000 R9: ffff9ac2422eeea0
R10: ffff9ac256fda9d8 R11: 0000000000549921 R12: ffff9ac2422eeea0
R13: ffff9ac251cd23c8 R14: ffff9ac24269a800 R15: ffff9ac251cd2150
ORIG_RAX: ffffffff8a1719e4 CS: 0206 SS: ffffffff8a1719c8
bt: WARNING: possibly bogus exception frame
Do you know how this happened? I would be grateful if you could fix it.
Thanks!
--
With Best Regards,
Baokun Li
.
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