linux-kernel - Re: kvm: WARNING in nested_vmx

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Date:   Wed, 1 Mar 2017 10:44:49 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        KVM list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jim Mattson <jmattson@...gle.com>,
        Steve Rutherford <srutherford@...gle.com>,
        Haozhong Zhang <haozhong.zhang@...el.com>,
        Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: kvm: WARNING in nested_vmx_vmexit

On Wed, Mar 1, 2017 at 7:13 AM, Wanpeng Li <kernellwp@...il.com> wrote:
> 2017-02-28 20:15 GMT+08:00 Dmitry Vyukov <dvyukov@...gle.com>:
>> Hello,
>>
>> The following program triggers WARNING in nested_vmx_vmexit:
>> https://gist.githubusercontent.com/dvyukov/16b946d7dc703bb07b9b933f12fb8a6e/raw/dac60506feb8dd9dd22828c486e46ee8a5e30f13/gistfile1.txt
>>
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 1 PID: 27742 at arch/x86/kvm/vmx.c:11029
>> nested_vmx_vmexit+0x5c35/0x74d0 arch/x86/kvm/vmx.c:11029
>> CPU: 1 PID: 27742 Comm: a.out Not tainted 4.10.0+ #229
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:15 [inline]
>>  dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
>>  panic+0x1fb/0x412 kernel/panic.c:179
>>  __warn+0x1c4/0x1e0 kernel/panic.c:540
>>  warn_slowpath_null+0x2c/0x40 kernel/panic.c:583
>>  nested_vmx_vmexit+0x5c35/0x74d0 arch/x86/kvm/vmx.c:11029
>>  vmx_leave_nested arch/x86/kvm/vmx.c:11136 [inline]
>>  vmx_set_msr+0x1565/0x1910 arch/x86/kvm/vmx.c:3324
>>  kvm_set_msr+0xd4/0x170 arch/x86/kvm/x86.c:1099
>>  do_set_msr+0x11e/0x190 arch/x86/kvm/x86.c:1128
>>  __msr_io arch/x86/kvm/x86.c:2577 [inline]
>>  msr_io+0x24b/0x450 arch/x86/kvm/x86.c:2614
>>  kvm_arch_vcpu_ioctl+0x35b/0x46a0 arch/x86/kvm/x86.c:3497
>>  kvm_vcpu_ioctl+0x232/0x1120 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2721
>>  vfs_ioctl fs/ioctl.c:43 [inline]
>>  do_vfs_ioctl+0x1bf/0x1790 fs/ioctl.c:683
>>  SYSC_ioctl fs/ioctl.c:698 [inline]
>>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689
>>  entry_SYSCALL_64_fastpath+0x1f/0xc2
>> RIP: 0033:0x451229
>> RSP: 002b:00007fc1e7ebec98 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000451229
>> RDX: 0000000020aecfe8 RSI: 000000004008ae89 RDI: 0000000000000008
>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
>> R13: 0000000000000000 R14: 00007fc1e7ebf9c0 R15: 00007fc1e7ebf700
>>
>>
>> On commit e5d56efc97f8240d0b5d66c03949382b6d7e5570
>
> I git checkout to this commit for linus tree, however the line number
> 11029 doesn't match any warning, and there are several warnings in the
> function nested_vmx_vmexit(), could you point out which one?

Ah sorry, I have some local diff.
So now I am on 86292b33d4b79ee03e2f43ea0381ef85f077c760 and here is my diff:
https://gist.githubusercontent.com/dvyukov/6bb88c6e3584c3fd989df01386efcb74/raw/1ae08a3a682ad9467de5eb7fb96d457db514f9d2/gistfile1.txt

The warning is:

        /* trying to cancel vmlaunch/vmresume is a bug */
        WARN_ON_ONCE(vmx->nested.nested_run_pending);