Re: kvm: WARNING in em_jmp_far

[Paolo Bonzini <pbonzini@redhat.com>]

On 15/11/2016 06:39, Nadav Amit wrote:
> 
>> On Nov 14, 2016, at 9:30 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
>>
>> On Tue, Nov 15, 2016 at 6:24 AM, Nadav Amit <nadav.amit@gmail.com> wrote:
>>>
>>>> On Nov 14, 2016, at 9:06 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
>>>>
>>>> Hello,
>>>>
>>>> The following program triggers WARNING in em_jmp_far:
>>>> https://gist.githubusercontent.com/dvyukov/16bfd3d68fa7d5461101ef74e07796e4/raw/e6d663980681f2c5838ff6cd361cede7d3204838/gistfile1.txt
>>>>
>>>>
>>>> WARNING: CPU: 1 PID: 15748 at arch/x86/kvm/emulate.c:2128 em_jmp_far+0x4a7/0x530
>>>
>>> I don’t know how to “read” the test, but it seems that this warning
>>> can be triggered if CS base/limit cause a #GP exception when EIP
>>> is loaded.
>>>
>>> I think it safe to remove this warning (which I introduced) as well as
>>> the redundant “return rc” that follows it. The code should handle the
>>> emulation correctly regardless of the warning.
>>
>> There was also a similar WARNING in em_ret_far:
>> https://groups.google.com/forum/#!msg/syzkaller/o5ZftARBhrs/r1ivQ-HtBgAJ
>>
>> Please mail a fix and add a test.
> 
> I am sorry, but I don’t think my current employer allows me to contribute
> to KVM in such a manner.

No problem, we can take care of it.

Paolo