linux-kernel - Re: [syzbot] upstream boot error: WARNING in kvm

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Message-ID: <CACT4Y+a54q=WzJU9UgzW1P6-xvJqrTJ9doXcqCgyu+MPBFFL=w@mail.gmail.com>
Date:   Sat, 6 Mar 2021 12:37:37 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+a4c8bc1d1dc7b620630d@...kaller.appspotmail.com>
Cc:     Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, KVM list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>, wanpengli@...cent.com,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [syzbot] upstream boot error: WARNING in kvm_wait

On Fri, Mar 5, 2021 at 9:56 PM syzbot
<syzbot+a4c8bc1d1dc7b620630d@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    280d542f Merge tag 'drm-fixes-2021-03-05' of git://anongit..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=138c7a92d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=dc4003509ab3fc78
> dashboard link: https://syzkaller.appspot.com/bug?extid=a4c8bc1d1dc7b620630d
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+a4c8bc1d1dc7b620630d@...kaller.appspotmail.com

+Mark, I've enabled CONFIG_DEBUG_IRQFLAGS on syzbot and it led to this breakage.
Is it a bug in kvm_wait or in the debugging code itself? If it's a
real bug, I would assume it's pretty bad as it happens all the time.


> ------------[ cut here ]------------
> raw_local_irq_restore() called with IRQs enabled
> WARNING: CPU: 2 PID: 213 at kernel/locking/irqflag-debug.c:10 warn_bogus_irq_restore+0x1d/0x20 kernel/locking/irqflag-debug.c:10
> Modules linked in:
> CPU: 2 PID: 213 Comm: kworker/u17:4 Not tainted 5.12.0-rc1-syzkaller #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
> Workqueue: events_unbound call_usermodehelper_exec_work
>
> RIP: 0010:warn_bogus_irq_restore+0x1d/0x20 kernel/locking/irqflag-debug.c:10
> Code: be ff cc cc cc cc cc cc cc cc cc cc cc 80 3d e4 38 af 04 00 74 01 c3 48 c7 c7 a0 8f 6b 89 c6 05 d3 38 af 04 01 e8 e7 b9 be ff <0f> 0b c3 48 39 77 10 0f 84 97 00 00 00 66 f7 47 22 f0 ff 74 4b 48
> RSP: 0000:ffffc90000fe7770 EFLAGS: 00010286
>
> RAX: 0000000000000000 RBX: ffffffff8c0e9c68 RCX: 0000000000000000
> RDX: ffff8880116bc3c0 RSI: ffffffff815c0cf5 RDI: fffff520001fcee0
> RBP: 0000000000000200 R08: 0000000000000000 R09: 0000000000000001
> R10: ffffffff815b9a5e R11: 0000000000000000 R12: 0000000000000003
> R13: fffffbfff181d38d R14: 0000000000000001 R15: ffff88802cc36000
> FS:  0000000000000000(0000) GS:ffff88802cc00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000000 CR3: 000000000bc8e000 CR4: 0000000000150ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  kvm_wait arch/x86/kernel/kvm.c:860 [inline]
>  kvm_wait+0xc9/0xe0 arch/x86/kernel/kvm.c:837
>  pv_wait arch/x86/include/asm/paravirt.h:564 [inline]
>  pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline]
>  __pv_queued_spin_lock_slowpath+0x8b8/0xb40 kernel/locking/qspinlock.c:508
>  pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:554 [inline]
>  queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
>  queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
>  do_raw_spin_lock+0x200/0x2b0 kernel/locking/spinlock_debug.c:113
>  spin_lock include/linux/spinlock.h:354 [inline]
>  copy_fs_struct+0x1c8/0x340 fs/fs_struct.c:123
>  copy_fs kernel/fork.c:1443 [inline]
>  copy_process+0x4dc2/0x6fd0 kernel/fork.c:2088
>  kernel_clone+0xe7/0xab0 kernel/fork.c:2462
>  kernel_thread+0xb5/0xf0 kernel/fork.c:2514
>  call_usermodehelper_exec_work kernel/umh.c:172 [inline]
>  call_usermodehelper_exec_work+0xcc/0x180 kernel/umh.c:158
>  process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
>  worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
>  kthread+0x3b1/0x4a0 kernel/kthread.c:292
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
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