From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH 0/16 v6] PCI: Linux kernel SR-IOV support Date: Fri, 07 Nov 2008 16:21:33 +0100 Message-ID: <87d4h7pnnm.fsf@basil.nowhere.org> References: <20081106154351.GA30459@kroah.com> <894107.30288.qm@web45108.mail.sp1.yahoo.com> <20081106164919.GA4099@kroah.com> <0199E0D51A61344794750DC57738F58E5E26F996C4@GVW1118EXC.americas.hpqcorp.net> <20081106183630.GD11773@parisc-linux.org> <491371F0.7020805@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Matthew Wilcox , "Fischer, Anna" , Greg KH , H L , "randy.dunlap@oracle.com" , "grundler@parisc-linux.org" , "Chiang, Alexander" , "linux-pci@vger.kernel.org" , "rdreier@cisco.com" , "linux-kernel@vger.kernel.org" , "jbarnes@virtuousgeek.org" , "virtualization@lists.linux-foundation.org" , "kvm@vger.kernel.org" , "mingo@elte.hu" To: Anthony Liguori Return-path: In-Reply-To: <491371F0.7020805@codemonkey.ws> (Anthony Liguori's message of "Thu, 06 Nov 2008 16:38:40 -0600") Sender: linux-pci-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Anthony Liguori writes: > > What we would rather do in KVM, is have the VFs appear in the host as > standard network devices. We would then like to back our existing PV > driver to this VF directly bypassing the host networking stack. A key > feature here is being able to fill the VF's receive queue with guest > memory instead of host kernel memory so that you can get zero-copy > receive traffic. This will perform just as well as doing passthrough > (at least) and avoid all that ugliness of dealing with SR-IOV in the > guest. But you shift a lot of ugliness into the host network stack again. Not sure that is a good trade off. Also it would always require context switches and I believe one of the reasons for the PV/VF model is very low latency IO and having heavyweight switches to the host and back would be against that. -Andi -- ak@linux.intel.com