linux-kernel - Re: kvm crash on 5.7-rc1 and later

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1418b143-7563-9fd7-ad94-bfab86c0862c@gmail.com>
Date:   Sun, 12 Jul 2020 07:54:23 -0400
From:   Woody Suwalski <terraluna977@...il.com>
To:     Xiaoyao Li <xiaoyao.li@...el.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     pbonzini@...hat.com, LKML <linux-kernel@...r.kernel.org>,
        fenghua.yu@...el.com, Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: kvm crash on 5.7-rc1 and later

Xiaoyao Li wrote:
> On 7/12/2020 2:21 AM, Peter Zijlstra wrote:
>> On Fri, Jul 03, 2020 at 11:15:31AM -0400, Woody Suwalski wrote:
>>> I am observing a 100% reproducible kvm crash on kernels starting with
>>> 5.7-rc1, always with the same opcode 0000.
>>> It happens during wake up from the host suspended state. Worked OK 
>>> on 5.6
>>> and older.
>>> The host is based on Debian testing, Thinkpad T440, i5 cpu.
>>>
>>> [   61.576664] kernel BUG at arch/x86/kvm/x86.c:387!
>>> [   61.576672] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
>>> [   61.576678] CPU: 0 PID: 3851 Comm: qemu-system-x86 Not tainted 
>>> 5.7-pingu
>>> #0
>>> [   61.576680] Hardware name: LENOVO 20B6005JUS/20B6005JUS, BIOS 
>>> GJETA4WW
>>> (2.54 ) 03/27/2020
>>> [   61.576700] RIP: 0010:kvm_spurious_fault+0xa/0x10 [kvm]
>>>
>>> Crash results in a dead kvm and occasionally a very unstable system.
>>>
>>> Bisecting the problem between v5.6 and v5.7-rc1 points to
>>>
>>> commit 6650cdd9a8ccf00555dbbe743d58541ad8feb6a7
>>> Author: Peter Zijlstra (Intel) <peterz@...radead.org>
>>> Date:   Sun Jan 26 12:05:35 2020 -0800
>>>
>>>      x86/split_lock: Enable split lock detection by kernel
>>>
>>> Reversing that patch seems to actually "cure" the issue.
>>>
>>> The problem is present in all kernels past 5.7-rc1, however the 
>>> patch is not
>>> reversing directly in later source trees, so can not retest the 
>>> logic on
>>> recent kernels.
>>>
>>> Peter, would you have idea how to debug that (or even better - would 
>>> you
>>> happen to know the fix)?
>>>
>>> I have attached dmesg logs from a "good" 5.6.9 kernel, and then 
>>> "bad" 5.7.0
>>> and 5.8-rc3
>>
>> I have no clue about kvm. Nor do I actually have hardware with SLD on.
>> I've Cc'ed a bunch of folks who might have more ideas.
>>
>
> I think this bug is the same as the one found by Sean, and is already 
> fixed in 5.8-rc4.
>
> https://lore.kernel.org/kvm/20200605192605.7439-1-sean.j.christopherson@intel.com/ 
>

You are right, kvm works OK on 5.8-rc4.
The fix will need to be backported to 5.7.

Thanks, Woody