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Subject: Re: Re: WARNING in x86_emulate_insn
To: Wanpeng Li <kernellwp@gmail.com>, Tianyu Lan <lantianyu1986@gmail.com>
Cc: Jim Mattson <jmattson@google.com>, Dmitry Vyukov <dvyukov@google.com>,
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From: "Lan, Tianyu" <tianyu.lan@intel.com>
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Date: Sat, 9 Dec 2017 13:44:02 +0800
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On 12/8/2017 5:27 PM, Wanpeng Li wrote:
> 2017-12-08 16:28 GMT+08:00 Tianyu Lan <lantianyu1986@gmail.com>:
>> Hi Jim&Wanpeng:
>>           Thanks for your help.
>>
>> 2017-12-08 5:25 GMT+08:00 Jim Mattson <jmattson@google.com>:
>>> Try disabling the module parameter, "unrestricted_guest." Make sure
>>> that the module parameter, "emulate_invalid_guest_state" is enabled.
>>> This combination allows userspace to feed invalid guest state into the
>>> in-kernel emulator.
>>
>> Yes, you are right. I need to disable unrestricted_guest to reproduce the issue.
> 
> I can observe ctxt->exception.vector == 0xff which triggers Dmitry's
> report. Do you figure out the reason?
> 

Yes, this is caused by that emulation callback returns error code while
not emulate exception and not set exception vector.
ctxt->exception.vector is default to be 0xff in emulate instruction code
path.