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Tue, 20 Sep 2022 04:12:47 -0400 X-MC-Unique: bxVL6sJTN7KVRcgN6p8H-w-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4E2CD855308; Tue, 20 Sep 2022 08:12:47 +0000 (UTC) Received: from [10.39.208.16] (unknown [10.39.208.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 88642C15BBD; Tue, 20 Sep 2022 08:12:46 +0000 (UTC) Message-ID: Date: Tue, 20 Sep 2022 10:12:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [PATCH] vhost: use try_lock in rte_vhost_vring_call To: "Liu, Changpeng" , "dev@dpdk.org" Cc: "Xia, Chenbo" References: <20220906022225.17215-1-changpeng.liu@intel.com> <2a63f996-84f4-434f-1b19-5dd035870e9d@redhat.com> From: Maxime Coquelin In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On 9/20/22 09:45, Liu, Changpeng wrote: > > >> -----Original Message----- >> From: Maxime Coquelin >> Sent: Tuesday, September 20, 2022 3:35 PM >> To: Liu, Changpeng ; dev@dpdk.org >> Cc: Xia, Chenbo >> Subject: Re: [PATCH] vhost: use try_lock in rte_vhost_vring_call >> >> >> >> On 9/20/22 09:29, Liu, Changpeng wrote: >>> Hi Maxime, >>> >>>> -----Original Message----- >>>> From: Maxime Coquelin >>>> Sent: Tuesday, September 20, 2022 3:19 PM >>>> To: Liu, Changpeng ; dev@dpdk.org >>>> Cc: Xia, Chenbo >>>> 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 >>>>> --- >>>>> 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? > Here is the commit introducing this issue > c5736998305d ("vhost: fix missing virtqueue lock protection") > Bugzilla ID: 1015 Ok, it cannot be reverted, as it prevents some undefined behaviors/crashes. >> >> Note that if we introduce a new API, it won't be backported to stable >> branches. > I understand, but do we have better idea in short time? we're planning > to release SPDK 22.09 recently. You can have another thread that sends the call? >> >> >>> 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 >>> >