From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58375) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eFVyx-00021k-7c for qemu-devel@nongnu.org; Thu, 16 Nov 2017 21:02:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eFVyu-0005bq-5U for qemu-devel@nongnu.org; Thu, 16 Nov 2017 21:02:15 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:2730) by eggs.gnu.org with esmtps (TLS1.0:RSA_ARCFOUR_SHA1:16) (Exim 4.71) (envelope-from ) id 1eFVyt-0005ZG-KH for qemu-devel@nongnu.org; Thu, 16 Nov 2017 21:02:12 -0500 Message-ID: <5A0E4310.2060803@huawei.com> Date: Fri, 17 Nov 2017 10:01:52 +0800 From: "Longpeng (Mike)" MIME-Version: 1.0 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> <55f2edb1-1fe3-d03f-7f4f-418a3b15997a@redhat.com> In-Reply-To: <55f2edb1-1fe3-d03f-7f4f-418a3b15997a@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit 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: Jason Wang Cc: "Huangweidong (C)" , "stefanha@redhat.com" , "mst@redhat.com" , "qemu-devel@nongnu.org" , "Wangjing (King, Euler)" , "Gonglei (Arei)" , "Longpeng(Mike)" On 2017/11/16 20:04, Jason Wang wrote: > > > On 2017年11月16日 17:32, Longpeng (Mike) wrote: >> Hi Jason, >> >> On 2017/11/16 17:13, Jason Wang wrote: >> >>> >>> On 2017年11月16日 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 that 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 queue 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=0, >> so vq->desc_phys=0, then vq->desc='a avail HVA'(which is the start addr of >> pc.ram). >> >> vq->desc_size = s = l = virtio_queue_get_desc_size(vdev, idx); >> vq->desc_phys = a = virtio_queue_get_desc_addr(vdev, idx); >> vq->desc = vhost_memory_map(dev, a, &l, 0); >> if (!vq->desc || l != s) { >> r = -ENOMEM; >> goto fail_alloc_desc; >> } >> ..... >> r = vhost_virtqueue_set_addr(dev, vq, vhost_vq_index, dev->log_enabled); >> if (r < 0) { >> r = -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 queues any > more. But we should have a complete solution. The main problem is when vhost > need to be started. For legacy device, there's no easy way to detect whether or > not a specific virtqueue is ready to be used. For modern device, we can probably > do this through queue_enable (but this is not implemented in current code). > Can we initialize the vring.desc/vring.avail/vring.used to -1, then we can detect whether or not a specific vq is ready to be used by check the addr of its tables is -1 or not ? Initialize to 0 is not suitable, because we don't know whether the guest set GPA 0 or the guest not initialize this vq. > Thanks > >> >>> Thanks >>> >>>> Thanks, >>>> -Gonglei >>>> >>> >>> >>> >>> . >>> >> > > > . > -- Regards, Longpeng(Mike)