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

From Paolo Bonzini <pbonzini@redhat.com>
Newsgroups linux.kernel
Subject Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration
Date 2017-02-24 11:10 +0100
Message-ID <tekZ4-72W-17@gated-at.bofh.it> (permalink)
References (6 earlier) <tedNU-1Pt-19@gated-at.bofh.it> <tedNU-1Pt-21@gated-at.bofh.it> <tedNU-1Pt-3@gated-at.bofh.it> <tekw2-6Db-3@gated-at.bofh.it> <tekZ4-72W-15@gated-at.bofh.it>
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On 24/02/2017 10:59, Greg KH wrote:
> On Fri, Feb 24, 2017 at 05:35:17PM +0800, Herongguang (Stephen) wrote:
>>
>>
>> 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?
> 
> If the KVM maintainers say it is ok to do so, yes, I will.

Yes, he beat me by minutes. :)

Paolo

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Thread

Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration "Herongguang (Stephen)" <herongguang.he@huawei.com> - 2017-02-24 03:30 +0100
  Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration "Herongguang (Stephen)" <herongguang.he@huawei.com> - 2017-02-24 10:40 +0100
    Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration Greg KH <gregkh@linuxfoundation.org> - 2017-02-24 11:10 +0100
    Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration Greg KH <gregkh@linuxfoundation.org> - 2017-02-24 11:10 +0100
      Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration Paolo Bonzini <pbonzini@redhat.com> - 2017-02-24 11:10 +0100
  Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration Paolo Bonzini <pbonzini@redhat.com> - 2017-02-24 16:20 +0100
    Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration "Herongguang (Stephen)" <herongguang.he@huawei.com> - 2017-02-25 02:50 +0100
      Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration "Huang, Kai" <kai.huang@linux.intel.com> - 2017-02-27 08:50 +0100
  Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration Chris Friesen <chris.friesen@windriver.com> - 2017-02-24 16:20 +0100

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