From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40785) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dKczj-0006JQ-3t for qemu-devel@nongnu.org; Mon, 12 Jun 2017 23:59:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dKczg-0003da-3q for qemu-devel@nongnu.org; Mon, 12 Jun 2017 23:59:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53338) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dKczf-0003dJ-UI for qemu-devel@nongnu.org; Mon, 12 Jun 2017 23:59:52 -0400 From: Jason Wang References: <1496653049-44530-1-git-send-email-wei.w.wang@intel.com> <20170605182514-mutt-send-email-mst@kernel.org> <5937511D.5070205@intel.com> <20170608220006-mutt-send-email-mst@kernel.org> <593A0F47.5080806@intel.com> <593E5F46.5080704@intel.com> <20170612234035-mutt-send-email-mst@kernel.org> <593F57C0.9080701@intel.com> <4639c51b-32a6-3528-2ed6-c5f6296b6300@redhat.com> <593F6133.9050804@intel.com> <65faf3f9-a839-0b04-c740-6b2a60a51cf6@redhat.com> Message-ID: Date: Tue, 13 Jun 2017 11:59:34 +0800 MIME-Version: 1.0 In-Reply-To: <65faf3f9-a839-0b04-c740-6b2a60a51cf6@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [virtio-dev] Re: [PATCH v1] virtio-net: enable configurable tx queue size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wei Wang , "Michael S. Tsirkin" Cc: virtio-dev@lists.oasis-open.org, stefanha@gmail.com, armbru@redhat.com, jan.scheurich@ericsson.com, qemu-devel@nongnu.org, marcandre.lureau@gmail.com, pbonzini@redhat.com On 2017=E5=B9=B406=E6=9C=8813=E6=97=A5 11:55, Jason Wang wrote: > > > On 2017=E5=B9=B406=E6=9C=8813=E6=97=A5 11:51, Wei Wang wrote: >> On 06/13/2017 11:19 AM, Jason Wang wrote: >>> >>> >>> On 2017=E5=B9=B406=E6=9C=8813=E6=97=A5 11:10, Wei Wang wrote: >>>> On 06/13/2017 04:43 AM, Michael S. Tsirkin wrote: >>>>> On Mon, Jun 12, 2017 at 05:30:46PM +0800, Wei Wang wrote: >>>>>> Ping for comments, thanks. >>>>> This was only posted a week ago, might be a bit too short for some >>>>> people. >>>> OK, sorry for the push. >>>>> A couple of weeks is more reasonable before you ping. Also, I >>>>> sent a bunch of comments on Thu, 8 Jun 2017. You should probably >>>>> address these. >>>>> >>>> I responded to the comments. The main question is that I'm not sure >>>> why we need the vhost backend to support VIRTIO_F_MAX_CHAIN_SIZE. >>>> IMHO, that should be a feature proposed to solve the possible issue >>>> caused by the QEMU implemented backend. >>> >>> The issue is what if there's a mismatch of max #sgs between qemu and=20 >>> vhost? >>> >> >> When the vhost backend is used, QEMU is not involved in the data=20 >> path. The vhost backend >> directly gets what is offered by the guest from the vq. FYI, qemu will try to fallback to userspace if there's something wrong=20 with vhost-kernel (e.g the IOMMU support). This doesn't work for=20 vhost-user actually, but it works for vhost-kernel. Thanks >> Why would there be a mismatch of >> max #sgs between QEMU and vhost, and what is the QEMU side max #sgs=20 >> used for? Thanks. > > You need query the backend max #sgs in this case at least. no? If not=20 > how do you know the value is supported by the backend? > > Thanks > >> >> Best, >> Wei >> >> > >