From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: Is fallback vhost_net to =?utf-8?Q?qem?= =?utf-8?Q?u_for_live_migrate_available=EF=BC=9F?= Date: Tue, 3 Sep 2013 11:55:56 +0300 Message-ID: <20130903085556.GD18901@redhat.com> References: <521C1DCF.5090202@huawei.com> <522174D7.6080903@huawei.com> <20130902075722.GZ15729@zion.uk.xensource.com> <52253B2B.6050909@huawei.com> <20130903084047.GF14104@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Qin Chuanyu , Anthony Liguori , jasowang@redhat.com, KVM list , netdev@vger.kernel.org, qianhuibin@huawei.com, "xen-devel@lists.xen.org" , wangfuhai@huawei.com, likunyun@huawei.com, liuyongan@huawei.com, liuyingdong@huawei.com To: Wei Liu Return-path: Content-Disposition: inline In-Reply-To: <20130903084047.GF14104@zion.uk.xensource.com> Sender: kvm-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, Sep 03, 2013 at 09:40:48AM +0100, Wei Liu wrote: > On Tue, Sep 03, 2013 at 09:28:11AM +0800, Qin Chuanyu wrote: > > On 2013/9/2 15:57, Wei Liu wrote: > > >On Sat, Aug 31, 2013 at 12:45:11PM +0800, Qin Chuanyu wrote: > > >>On 2013/8/30 0:08, Anthony Liguori wrote: > > >>>Hi Qin, > > >> > > >>>>By change the memory copy and notify mechanism =EF=BC=8Ccurrent= ly virtio-net with > > >>>>vhost_net could run on Xen with good performance=E3=80=82 > > >>> > > >>>I think the key in doing this would be to implement a property > > >>>ioeventfd and irqfd interface in the driver domain kernel. Just > > >>>hacking vhost_net with Xen specific knowledge would be pretty na= sty > > >>>IMHO. > > >>> > > >>Yes, I add a kernel module which persist virtio-net pio_addr and > > >>msix address as what kvm module did. Guest wake up vhost thread b= y > > >>adding a hook func in evtchn_interrupt. > > >> > > >>>Did you modify the front end driver to do grant table mapping or= is > > >>>this all being done by mapping the domain's memory? > > >>> > > >>There is nothing changed in front end driver. Currently I use > > >>alloc_vm_area to get address space=EF=BC=8C and map the domain's = memory as > > >>what what qemu did. > > >> > > > > > >You mean you're using xc_map_foreign_range and friends in the back= end to > > >map guest memory? That's not very desirable as it violates Xen's > > >security model. It would not be too hard to pass grant references > > >instead of guest physical memory address IMHO. > > > > > In fact, I did what virtio-net have done in Qemu. I think security > > is a pseudo question because Dom0 is under control. > >=20 >=20 > Consider that you might have driver domains. Not every domain is unde= r > control or trusted. I don't see anything that will prevent using driver domains here. > Also consider that security model like XSM can be > used to audit operations to enhance security so your foreign mapping > approach might not always work. It could be nice to have as an option, sure. XSM is disabled by default though so I don't think lack of support for that makes it a prototype. > In short term foreign mapping can save you some time implementing the > prototype. > In long term using grant table is the proper way to go. And > IMHO the benifit outweights the cost. >=20 > Wei. I'm guessing direct access could be quite a bit faster. But someone would have to implement your idea in order to do a cost/benefit analysis. > > Host could access memory of guest in KVM much easier than Xen, > > but I hadn't heard someone said KVM is un-secret. > >=20 > > Regards > > Qin chuanyu > >=20 > >=20 > > -- > > To unsubscribe from this list: send the line "unsubscribe netdev" i= n > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html