nmi isn't supported in dom0, fallback to general all cpu backtrace code.
Without fix, on xapic system, sysrq+l, no backtrace is showed.
On x2apic enabled system, got NULL pointer dereference as below.
SysRq : Show backtrace of all active CPUs
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff8125e3cb>] memcpy+0xb/0x120
Call Trace:
[<ffffffff81039633>] ? __x2apic_send_IPI_mask+0x73/0x160
[<ffffffff8103973e>] x2apic_send_IPI_all+0x1e/0x20
[<ffffffff8103498c>] arch_trigger_all_cpu_backtrace+0x6c/0xb0
[<ffffffff81501be4>] ? _raw_spin_lock_irqsave+0x34/0x50
[<ffffffff8131654e>] sysrq_handle_showallcpus+0xe/0x10
[<ffffffff8131616d>] __handle_sysrq+0x7d/0x140
[<ffffffff81316230>] ? __handle_sysrq+0x140/0x140
[<ffffffff81316287>] write_sysrq_trigger+0x57/0x60
[<ffffffff811ca996>] proc_reg_write+0x86/0xc0
[<ffffffff8116dd8e>] vfs_write+0xce/0x190
[<ffffffff8116e3e5>] sys_write+0x55/0x90
[<ffffffff8150a242>] system_call_fastpath+0x16/0x1b
Signed-off-by: Zhenzhong Duan <zhenzhong.d...@oracle.com>
Tested-by: Tamon Shiose <tamon.shi...@oracle.com>
---
include/linux/nmi.h | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index db50840..b845757 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -32,6 +32,8 @@ static inline void touch_nmi_watchdog(void)
#ifdef arch_trigger_all_cpu_backtrace
static inline bool trigger_all_cpu_backtrace(void)
{
+ if (xen_domain())
+ return false;
arch_trigger_all_cpu_backtrace();
return true;
--
1.7.3
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