From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: "Liu, Changpeng" <changpeng.liu@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>
Cc: "Xia, Chenbo" <chenbo.xia@intel.com>
Subject: Re: [PATCH] vhost: use try_lock in rte_vhost_vring_call
Date: Tue, 20 Sep 2022 09:34:32 +0200 [thread overview]
Message-ID: <b281daaa-c07c-72cb-cb86-5c2fa3583001@redhat.com> (raw)
In-Reply-To: <PH0PR11MB5093F694F8E386CD6B5808ECEE4C9@PH0PR11MB5093.namprd11.prod.outlook.com>
On 9/20/22 09:29, Liu, Changpeng wrote:
> Hi Maxime,
>
>> -----Original Message-----
>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Sent: Tuesday, September 20, 2022 3:19 PM
>> To: Liu, Changpeng <changpeng.liu@intel.com>; dev@dpdk.org
>> Cc: Xia, Chenbo <chenbo.xia@intel.com>
>> Subject: Re: [PATCH] vhost: use try_lock in rte_vhost_vring_call
>>
>>
>>
>> On 9/6/22 04:22, Changpeng Liu wrote:
>>> Note that this function is in data path, so the thread context
>>> may not same as socket messages processing context, by using
>>> try_lock here, users can have another try in case of VQ's access
>>> lock is held by `vhost-events` thread.
>>>
>>> Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
>>> ---
>>> lib/vhost/vhost.c | 6 +++++-
>>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
>>> index 60cb05a0ff..072d2acb7b 100644
>>> --- a/lib/vhost/vhost.c
>>> +++ b/lib/vhost/vhost.c
>>> @@ -1329,7 +1329,11 @@ rte_vhost_vring_call(int vid, uint16_t vring_idx)
>>> if (!vq)
>>> return -1;
>>>
>>> - rte_spinlock_lock(&vq->access_lock);
>>> + if (!rte_spinlock_trylock(&vq->access_lock)) {
>>> + VHOST_LOG_CONFIG(dev->ifname, DEBUG,
>>> + "failed to kick guest, virtqueue busy.\n");
>>> + return -1;
>>> + }
>>>
>>> if (vq_is_packed(dev))
>>> vhost_vring_call_packed(dev, vq);
>>
>> I think that's problematic, because it will break other applications
>> that currently rely on the API to block until the call is done.
>>
>> Just some internal DPDK usage of this API:
>> ./drivers/vdpa/ifc/ifcvf_vdpa.c:871: rte_vhost_vring_call(internal->vid,
>> qid);
>> ./examples/vhost/virtio_net.c:236: rte_vhost_vring_call(dev->vid, queue_id);
>> ./examples/vhost/virtio_net.c:446: rte_vhost_vring_call(dev->vid, queue_id);
>> ./examples/vhost_blk/vhost_blk.c:99:
>> rte_vhost_vring_call(task->ctrlr->vid, vq->id);
>> ./examples/vhost_blk/vhost_blk.c:134:
>> rte_vhost_vring_call(task->ctrlr->vid, vq->id);
>>
>> This change will break all the above uses.
>>
>> And that's not counting external projects.
>>
>> ou should better introduce a new API that does not block.
> Could you add a new API to do this?
>
> I think we can use the new API in SPDK as a workaround, note that SPDK project is blocked for
> a while which can't be used with DPDK 22.05 or newer.
DPDK v22.05?
What is the commit introducing the regression?
Note that if we introduce a new API, it won't be backported to stable
branches.
> Vhost-blk and scsi devices are not same with vhost-net, we need to cover SeaBIOS and VM
> cases, so we need to start processing vrings after 1 vring is ready.
>>
>> Regards,
>> Maxime
>
next prev parent reply other threads:[~2022-09-20 7:34 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-06 2:22 Changpeng Liu
2022-09-06 21:15 ` Stephen Hemminger
2022-09-07 0:40 ` Liu, Changpeng
2022-09-20 7:12 ` Maxime Coquelin
2022-09-20 2:24 ` Xia, Chenbo
2022-09-20 2:34 ` Liu, Changpeng
2022-09-20 2:53 ` Xia, Chenbo
2022-09-20 3:00 ` Liu, Changpeng
2022-09-20 7:23 ` Maxime Coquelin
2022-09-20 7:30 ` Maxime Coquelin
2022-09-20 7:19 ` Maxime Coquelin
2022-09-20 7:29 ` Liu, Changpeng
2022-09-20 7:34 ` Maxime Coquelin [this message]
2022-09-20 7:45 ` Liu, Changpeng
2022-09-20 8:12 ` Maxime Coquelin
2022-09-20 8:43 ` Liu, Changpeng
2022-09-21 9:41 ` Maxime Coquelin
2022-09-21 9:52 ` Liu, Changpeng
2022-10-11 11:56 ` Maxime Coquelin
2022-10-12 6:40 ` [PATCH v2] vhost: add new `rte_vhost_vring_call_nonblock` API Changpeng Liu
2022-10-13 7:56 ` Maxime Coquelin
2022-10-17 6:46 ` Xia, Chenbo
2022-10-17 7:17 ` Liu, Changpeng
2022-10-17 7:14 ` [PATCH v3] " Changpeng Liu
2022-10-17 7:39 ` Xia, Chenbo
2022-10-17 7:50 ` Liu, Changpeng
2022-10-17 7:48 ` [PATCH v4] " Changpeng Liu
2022-10-19 5:27 ` Xia, Chenbo
2022-10-26 9:24 ` Xia, Chenbo
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