From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40441) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YQx8q-0005Ag-Tp for qemu-devel@nongnu.org; Thu, 26 Feb 2015 07:02:12 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YQx8m-0001jk-1t for qemu-devel@nongnu.org; Thu, 26 Feb 2015 07:02:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37958) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YQx8l-0001jY-QH for qemu-devel@nongnu.org; Thu, 26 Feb 2015 07:02:04 -0500 Date: Thu, 26 Feb 2015 13:01:53 +0100 From: "Michael S. Tsirkin" Message-ID: <20150226120153.GA31740@redhat.com> References: <47CEA9C0E570484FBF22EF0D7EBCE5B534A4984F@szxema505-mbs.china.huawei.com> <20150226093625.GA24766@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [Question] about vhost user Interface List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Nikolay Nikolaev Cc: "pbonzini@redhat.com" , "Gaohaifeng (A)" , "qemu-devel@nongnu.org" , "Lilijun (Jerry)" On Thu, Feb 26, 2015 at 01:55:54PM +0200, Nikolay Nikolaev wrote: > On Thu, Feb 26, 2015 at 11:36 AM, Michael S. Tsirkin w= rote: > > > > On Thu, Feb 26, 2015 at 09:30:40AM +0000, Gaohaifeng (A) wrote: > > > Hi > > > > > > I want to use pxe to install a guest os whose nic type is vhost u= ser. However > > > pxe rom doesn=E2=80=99t support msi-x interrupt, so qemu won=E2=80=99= t start vhost net. > > > > > > Call relationship: > > > > > > virtio_net_vhost_status-> vhost_net_query-> vhost_dev_query-> > > > virtio_pci_query_guest_notifiers -> msix_enabled > > > > > > > > > > > > In my test, I remove the msix check for vhost user interface and su= ccessfully > > > install the guest os by pxe. > > > > > > Is it OK to do like this and will it cause other problems? > > > > > > > > > > > > Thanks. > > > > > > Haifeng Gao > > > > > > > I think we should fix it. > > As a quick hack, you should be able to just use vhostforce. >=20 >=20 > But isn't that what vhostforce is for, runnign vhost with non > MSI-enabled guests? >=20 > regards, > Nikolay Nikolaev It isn't really. kernel vhost is more or less an optimization. since it performs slowly for non msi guests, it turns itself off for them by default, and you fall back to virtio in qemu which for non msi seems to be faster. to re-enable, set force to on. vhost user doesn't work with virtio in qemu, it should ignore vhostforce and just handle non msix guests. > > > > > > -- > > MST > >