From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36520) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eFIub-0006MT-KT for qemu-devel@nongnu.org; Thu, 16 Nov 2017 07:04:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eFIuV-0004xY-Nf for qemu-devel@nongnu.org; Thu, 16 Nov 2017 07:04:53 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51346) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eFIuV-0004wX-FG for qemu-devel@nongnu.org; Thu, 16 Nov 2017 07:04:47 -0500 References: <5A0D27D8.6050506@huawei.com> <2e0ddd76-3903-d715-9a86-73f1286322e7@redhat.com> <33183CC9F5247A488A2544077AF19020DA46E2A6@DGGEMA505-MBS.china.huawei.com> <6aaaca2b-81ef-a1c1-4745-830d008b3770@redhat.com> <5A0D5B1B.3080708@huawei.com> From: Jason Wang Message-ID: <55f2edb1-1fe3-d03f-7f4f-418a3b15997a@redhat.com> Date: Thu, 16 Nov 2017 20:04:34 +0800 MIME-Version: 1.0 In-Reply-To: <5A0D5B1B.3080708@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [Question] why need to start all queues in vhost_net_start List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Longpeng (Mike)" Cc: "Huangweidong (C)" , "stefanha@redhat.com" , "mst@redhat.com" , "qemu-devel@nongnu.org" , "Wangjing (King, Euler)" , "Gonglei (Arei)" , "Longpeng(Mike)" On 2017=E5=B9=B411=E6=9C=8816=E6=97=A5 17:32, Longpeng (Mike) wrote: > Hi Jason, > > On 2017/11/16 17:13, Jason Wang wrote: > >> >> On 2017=E5=B9=B411=E6=9C=8816=E6=97=A5 17:01, Gonglei (Arei) wrote: >>> No, Windows guest + vhost-user/DPDK. >>> >>> BTW pls see virtio spec in : >>> >>> "If VIRTIO_NET_F_MQ is negotiated, each of receiveq1. . .receiveqN th= at will >>> be used SHOULD be populated >>> with receive buffers." >>> >>> It is not mandatory that all queues must be initialized. >> I think not, since it said we should fill receive buffers for each que= ue which >> means we should initialize all queues. May Michael can clarify on this= . >> > > I think this doesn't matter, but QEMU should consider this scenario... > > For example, if one queues isn't initialized (Windows guest), the vring= .avail=3D0, > so vq->desc_phys=3D0, then vq->desc=3D'a avail HVA'(which is the start = addr of pc.ram). > > vq->desc_size =3D s =3D l =3D virtio_queue_get_desc_size(vdev, idx= ); > vq->desc_phys =3D a =3D virtio_queue_get_desc_addr(vdev, idx); > vq->desc =3D vhost_memory_map(dev, a, &l, 0); > if (!vq->desc || l !=3D s) { > r =3D -ENOMEM; > goto fail_alloc_desc; > } > ..... > r =3D vhost_virtqueue_set_addr(dev, vq, vhost_vq_index, dev->log_e= nabled); > if (r < 0) { > r =3D -errno; > goto fail_alloc; > } > > Then the HVA is send to the vhost-user. > > I think this is wrong, because the '0' here means guest driver doesn't = init this > queues, it should not be used to calculate the HVA for this vq. Yes, workaround is not hard if windows driver won't use the left 3=20 queues any more. But we should have a complete solution. The main=20 problem is when vhost need to be started. For legacy device, there's no=20 easy way to detect whether or not a specific virtqueue is ready to be=20 used. For modern device, we can probably do this through queue_enable=20 (but this is not implemented in current code). Thanks > >> Thanks >> >>> Thanks, >>> -Gonglei >>> >> >> >> >> . >> >