Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration

Herongguang (Stephen)
2017-02-24T09:36:05Z

On 2017/2/24 10:23, Herongguang (Stephen) wrote:
>
>
> On 2017/2/22 22:43, Paolo Bonzini wrote:
>>
>>
>> On 22/02/2017 14:31, Chris Friesen wrote:
>>>>>
>>>>
>>>> Can you reproduce it with kernel 4.8+? I'm suspecting commmit
>>>> 4e59516a12a6 ("kvm: vmx: ensure VMCS is current while enabling PML",
>>>> 2016-07-14) to be the fix.
>>>
>>> I can't easily try with a newer kernel, the software package we're using
>>> has kernel patches that would have to be ported.
>>>
>>> I'm at a conference, don't really have time to set up a pair of test
>>> machines from scratch with a custom kernel.
>>
>> Hopefully Gaohuai and Rongguang can help with this too.
>>
>> Paolo
>>
>> .
>>
> Yes, we are looking into and testing this.
>
> I think this can result in any memory corruption, if VM1 writes its
> PML buffer into VM2’s VMCS (since sched_in/sched_out notifier of VM1
> is not registered yet), then VM1 is destroyed (hence its PML buffer
> is freed back to kernel), after that, VM2 starts migration, so CPU
> logs VM2’s dirty GFNS into a freed memory, results in any memory corruption.
>
> As its severity, this commit (http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4e59516a12a6ef6dcb660cb3a3f70c64bd60cfec)
> is eligible to back port to kernel stable.

Hi, Greg, can you cherry pick commit 4e59516a12a6ef6dcb660cb3a3f70c64bd60cfec to 4.4-y?