From: Ilya Maximets <i.maximets@samsung.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: dev@dpdk.org, Huawei Xie <huawei.xie@intel.com>,
Dyasly Sergey <s.dyasly@samsung.com>,
Heetae Ahn <heetae82.ahn@samsung.com>,
Jianfeng Tan <jianfeng.tan@intel.com>,
Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [dpdk-dev] [PATCH] vhost: fix segfault on bad descriptor address.
Date: Mon, 11 Jul 2016 14:47:56 +0300 [thread overview]
Message-ID: <5783876C.1050103@samsung.com> (raw)
In-Reply-To: <20160711110503.GZ26521@yliu-dev.sh.intel.com>
On 11.07.2016 14:05, Yuanhan Liu wrote:
> On Mon, Jul 11, 2016 at 12:50:24PM +0300, Ilya Maximets wrote:
>> On 11.07.2016 11:38, Yuanhan Liu wrote:
>>> On Sun, Jul 10, 2016 at 09:17:31PM +0800, Yuanhan Liu wrote:
>>>> On Fri, Jul 08, 2016 at 02:48:56PM +0300, Ilya Maximets wrote:
>>>>>
>>>>> Another point is that crash constantly happens on queue_id=3 (second RX queue) in
>>>>> my scenario. It is newly allocated virtqueue while reconfiguration from rxq=1 to
>>>>> rxq=2.
>>>>
>>>> That's a valuable message: what's your DPDK HEAD commit while triggering
>>>> this issue?
>>
>> fbfd99551ca3 ("mbuf: add raw allocation function")
>>
>>>
>>> I guess I have understood what goes wrong in you case.
>>>
>>> I would guess that your vhost has 2 queues (here I mean queue-pairs,
>>> including one Tx and Rx queue; below usage is the same) configured,
>>> so does to your QEMU. However, you just enabled 1 queue while starting
>>> testpmd inside the guest, and you want to enable 2 queues by running
>>> following testpmd commands:
>>>
>>> stop
>>> port stop all
>>> port config all rxq 2
>>> port config all txq 2
>>> port start all
>>>
>>> Badly, that won't work for current virtio PMD implementation, and what's
>>> worse, it triggers a vhost crash, the one you saw.
>>>
>>> Here is how it comes. Since you just enabled 1 queue while starting
>>> testpmd, it will setup 1 queue only, meaning only one queue's **valid**
>>> information will be sent to vhost. You might see SET_VRING_ADDR
>>> (and related vhost messages) for the other queue as well, but they
>>> are just the dummy messages: they don't include any valid/real
>>> information about the 2nd queue: the driver don't setup it after all.
>>>
>>> So far, so good. It became broken when you run above commands. Those
>>> commands do setup for the 2nd queue, however, they failed to trigger
>>> the QEMU virtio device to start the vhost-user negotiation, meaning
>>> no SET_VRING_ADDR will be sent for the 2nd queue, leaving vhost
>>> untold and not updated.
>>>
>>> What's worse, above commands trigger the QEMU to send SET_VRING_ENABLE
>>> messages, to enable all the vrings. And since the vrings for the 2nd
>>> queue are not properly configured, the crash happens.
>>
>> Hmm, why 2nd queue works properly with my fix to vhost in this case?
>
> Hmm, really? You are sure that data flows in your 2nd queue after those
> commands? From what I know is that your patch just avoid a crash, but
> does not fix it.
Oh, sorry. Yes, it doesn't work. With my patch applied I have a QEMU hang.
>>> So maybe we should do virtio reset on port start?
>>
>> I guess it was removed by this patch:
>> a85786dc816f ("virtio: fix states handling during initialization").
>
> Seems yes.
>
> --yliu
>
>
next prev parent reply other threads:[~2016-07-11 11:47 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-20 12:50 Ilya Maximets
2016-05-23 10:57 ` Yuanhan Liu
2016-05-23 11:04 ` Ilya Maximets
2016-05-30 11:05 ` Ilya Maximets
2016-05-30 14:25 ` Yuanhan Liu
2016-05-31 9:12 ` Ilya Maximets
2016-05-30 12:00 ` Tan, Jianfeng
2016-05-30 12:24 ` Ilya Maximets
2016-05-31 6:53 ` Tan, Jianfeng
2016-05-31 9:10 ` Ilya Maximets
2016-05-31 22:06 ` Rich Lane
2016-06-02 10:46 ` Ilya Maximets
2016-06-02 16:22 ` Rich Lane
2016-06-03 6:01 ` Ilya Maximets
2016-07-01 7:35 ` Yuanhan Liu
2016-07-06 11:19 ` Ilya Maximets
2016-07-06 12:24 ` Yuanhan Liu
2016-07-08 11:48 ` Ilya Maximets
2016-07-10 13:17 ` Yuanhan Liu
2016-07-11 8:38 ` Yuanhan Liu
2016-07-11 9:50 ` Ilya Maximets
2016-07-11 11:05 ` Yuanhan Liu
2016-07-11 11:47 ` Ilya Maximets [this message]
2016-07-12 2:43 ` Yuanhan Liu
2016-07-12 5:53 ` Ilya Maximets
2016-07-13 7:34 ` Ilya Maximets
2016-07-13 8:47 ` Yuanhan Liu
2016-07-13 15:54 ` Rich Lane
2016-07-14 1:42 ` Yuanhan Liu
2016-07-14 4:38 ` Ilya Maximets
2016-07-14 8:18 ` [dpdk-dev] [PATCH v2] " Ilya Maximets
2016-07-15 6:17 ` Yuanhan Liu
2016-07-15 7:23 ` Ilya Maximets
2016-07-15 8:40 ` Yuanhan Liu
2016-07-15 11:15 ` [dpdk-dev] [PATCH v3 0/2] " Ilya Maximets
2016-07-15 11:15 ` [dpdk-dev] [PATCH v3 1/2] vhost: fix using of bad return value on mergeable enqueue Ilya Maximets
2016-07-15 11:15 ` [dpdk-dev] [PATCH v3 2/2] vhost: do sanity check for ring descriptor address Ilya Maximets
2016-07-15 12:14 ` [dpdk-dev] [PATCH v3 0/2] vhost: fix segfault on bad " Yuanhan Liu
2016-07-15 19:37 ` Thomas Monjalon
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