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SubjectRe: kvm crash on 5.7-rc1 and later
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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@infradead.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

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