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Date:   Wed, 12 Aug 2020 10:57:17 +0200
From:   peterz@infradead.org
To:     Marco Elver <elver@google.com>
Cc:     =?iso-8859-1?Q?J=FCrgen_Gro=DF?= <jgross@suse.com>,
        Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        fenghua.yu@intel.com, "H. Peter Anvin" <hpa@zytor.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Luck, Tony" <tony.luck@intel.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        yu-cheng.yu@intel.com, sdeep@vmware.com,
        virtualization@lists.linux-foundation.org,
        kasan-dev <kasan-dev@googlegroups.com>,
        syzbot <syzbot+8db9e1ecde74e590a657@syzkaller.appspotmail.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Wei Liu <wei.liu@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH] x86/paravirt: Add missing noinstr to arch_local*()
 helpers
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On Wed, Aug 12, 2020 at 10:18:32AM +0200, peterz@infradead.org wrote:
> > 	 trace_hardirqs_restore+0x59/0x80 kernel/trace/trace_preemptirq.c:106
> > 	 rcu_irq_enter_irqson+0x43/0x70 kernel/rcu/tree.c:1074
> > 	 trace_irq_enable_rcuidle+0x87/0x120 include/trace/events/preemptirq.h:40
> > 	 trace_hardirqs_restore+0x59/0x80 kernel/trace/trace_preemptirq.c:106
> > 	 rcu_irq_enter_irqson+0x43/0x70 kernel/rcu/tree.c:1074
> > 	 trace_irq_enable_rcuidle+0x87/0x120 include/trace/events/preemptirq.h:40
> > 	 trace_hardirqs_restore+0x59/0x80 kernel/trace/trace_preemptirq.c:106
> > 	 rcu_irq_enter_irqson+0x43/0x70 kernel/rcu/tree.c:1074
> > 	 trace_irq_enable_rcuidle+0x87/0x120 include/trace/events/preemptirq.h:40
> > 	 trace_hardirqs_restore+0x59/0x80 kernel/trace/trace_preemptirq.c:106
> > 	 rcu_irq_enter_irqson+0x43/0x70 kernel/rcu/tree.c:1074
> > 
> > 	<... repeated many many times ...>
> > 
> > 	 trace_irq_enable_rcuidle+0x87/0x120 include/trace/events/preemptirq.h:40
> > 	 trace_hardirqs_restore+0x59/0x80 kernel/trace/trace_preemptirq.c:106
> > 	 rcu_irq_enter_irqson+0x43/0x70 kernel/rcu/tree.c:1074
> > 	Lost 500 message(s)!
> > 	BUG: stack guard page was hit at 00000000cab483ba (stack is 00000000b1442365..00000000c26f9ad3)
> > 	BUG: stack guard page was hit at 00000000318ff8d8 (stack is 00000000fd87d656..0000000058100136)
> > 	---[ end trace 4157e0bb4a65941a ]---
> 
> Wheee... recursion! Let me try and see if I can make something of that.

All that's needed is enabling the preemptirq tracepoints. Lemme go fix.