From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 3B8F7A00C3; Tue, 20 Sep 2022 09:34:41 +0200 (CEST) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id C8DE740DFB; Tue, 20 Sep 2022 09:34:40 +0200 (CEST) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by mails.dpdk.org (Postfix) with ESMTP id E41B84069B for ; Tue, 20 Sep 2022 09:34:39 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1663659279; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3VPLeG2WrPNyD7bD0tDs6syI795KhIL7nLmGM/afVkM=; b=Mfx+3VbmSegl4MmNahV60j3N2GnUGdCZS1yQ+VIrqgPJ3tv+54JDoXWdEGOmJX+yalYxCP 0pE79XwXmu0cmmqRBZO28jBqj1S2y5GC8yVL0Wi9oLCUJFpb1RAAkWjepJ+VTFKeearw0x 0adwP5oE3Z41nmYQB0U69GR02noixbA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-261-yZXntw0FO56Y-_rmtf2C-w-1; Tue, 20 Sep 2022 03:34:35 -0400 X-MC-Unique: yZXntw0FO56Y-_rmtf2C-w-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id AC531803791; Tue, 20 Sep 2022 07:34:34 +0000 (UTC) Received: from [10.39.208.16] (unknown [10.39.208.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E904840C2066; Tue, 20 Sep 2022 07:34:33 +0000 (UTC) Message-ID: Date: Tue, 20 Sep 2022 09:34:32 +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 10.11.54.1 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 09:29, 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? 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 >