OK.
On 30.05.2016 17:25, Yuanhan Liu wrote:
> Hi Ilya,
>
> Generically speaking, this patch looks good to me. But I guess still
> need more time to check this issue later; I still failed to reproduce
> it on my side after all. So, please allow a late merge.
>
> Thanks.
>
> --yliu
>
> On Mon, May 30, 2016 at 02:05:07PM +0300, Ilya Maximets wrote:
>> Ping.
>>
>> Best regards, Ilya Maximets.
>>
>> On 23.05.2016 14:04, Ilya Maximets wrote:
>>> On 23.05.2016 13:57, Yuanhan Liu wrote:
>>>> On Fri, May 20, 2016 at 03:50:04PM +0300, Ilya Maximets wrote:
>>>>> In current implementation guest application can reinitialize vrings
>>>>> by executing start after stop. In the same time host application
>>>>> can still poll virtqueue while device stopped in guest and it will
>>>>> crash with segmentation fault while vring reinitialization because
>>>>> of dereferencing of bad descriptor addresses.
>>>>>
>>>>> OVS crash for example:
>>>>> <------------------------------------------------------------------------>
>>>>> [test-pmd inside guest VM]
>>>>>
>>>>> testpmd> port stop all
>>>>> Stopping ports...
>>>>> Checking link statuses...
>>>>> Port 0 Link Up - speed 10000 Mbps - full-duplex
>>>>> Done
>>>>> testpmd> port config all rxq 2
>>>>> testpmd> port config all txq 2
>>>>> testpmd> port start all
>>>>> Configuring Port 0 (socket 0)
>>>>> Port 0: 52:54:00:CB:44:C8
>>>>> Checking link statuses...
>>>>> Port 0 Link Up - speed 10000 Mbps - full-duplex
>>>>> Done
>>>>
>>>> I actually didn't manage to reproduce it on my side, with the
>>>> vhost-example instead of OVS though. Is that all the commands
>>>> to reproduce it, and run them just after start test-pmd?
>>>
>>> Actually, I think, packet flow should be enabled while performing
>>> above actions and some traffic already should be sent through port
>>> to change last used idx on vhost side.
>>>
>>> Something like:
>>> start
>>> ..wait a while.. see that packets are flowing.
>>> stop
>>> port stop
>>> port config
>>> port config
>>> port start
>>>>
>>>>> [OVS on host]
>>>>> Program received signal SIGSEGV, Segmentation fault.
>>>>> rte_memcpy (n=2056, src=0xc, dst=0x7ff4d5247000) at rte_memcpy.h
>>>>>
>>>>> (gdb) bt
>>>>> #0 rte_memcpy (n=2056, src=0xc, dst=0x7ff4d5247000)
>>>>> #1 copy_desc_to_mbuf
>>>>> #2 rte_vhost_dequeue_burst
>>>>> #3 netdev_dpdk_vhost_rxq_recv
>>>>> ...
>>>>>
>>>>> (gdb) bt full
>>>>> #0 rte_memcpy
>>>>> ...
>>>>> #1 copy_desc_to_mbuf
>>>>> desc_addr = 0
>>>>> mbuf_offset = 0
>>>>> desc_offset = 12
>>>>> ...
>>>>> <------------------------------------------------------------------------>
>>>>>
>>>>> Fix that by checking addresses of descriptors before using them.
>>>>>
>>>>> Note: For mergeable buffers this patch checks only guest's address for
>>>>> zero, but in non-meargeable case host's address checked. This is done
>>>>> because checking of host's address in mergeable case requires additional
>>>>> refactoring to keep virtqueue in consistent state in case of error.
>>>>>
>>>>> Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
>>>>> ---
>>>>>
>>>>> Actually, current virtio implementation looks broken for me. Because
>>>>> 'virtio_dev_start' breaks virtqueue while it still available from the
>>>>> vhost
>>>>> side.
>>>>>
>>>>> There was 2 patches about this behaviour:
>>>>>
>>>>> 1. a85786dc816f ("virtio: fix states handling during initialization")
>>>>> 2. 9a0615af7746 ("virtio: fix restart")
>>>>>
>>>>> The second patch fixes somehow issue intoduced in the first patch, but
>>>>> actually
>>>>> also breaks vhost in the way described above.
>>>>> It's not pretty clear for me what to do in current situation with virtio,
>>>>> because it will be broken for guest application even if vhost will not
>>>>> crash.
>>>>>
>>>>> May be it'll be better to forbid stopping of virtio device and force user
>>>>> to
>>>>> exit and start again (may be implemented in hidden from user way)?
>>>>>
>>>>> This patch adds additional sane checks, so it should be applied anyway,
>>>>> IMHO.
>>>>
>>>> Agreed.
>>>>
>>>> --yliu
>>>>
>>>>
>
>
