From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33 Date: Sun, 27 Dec 2009 11:29:54 +0200 Message-ID: <4B372912.9050704@redhat.com> References: <4B1D4F29.8020309@gmail.com> <87637zdy9g.fsf@basil.nowhere.org> <4B30E654.40702@codemonkey.ws> <200912221701.56840.bzolnier@gmail.com> <4B30F214.80206@codemonkey.ws> <20091223065129.GA19600@elte.hu> <4B3248F9.5030504@gmail.com> <4B327F3A.9020101@redhat.com> <4B3334E1.9020401@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Ingo Molnar , Anthony Liguori , Bartlomiej Zolnierkiewicz , Andi Kleen , kvm@vger.kernel.org, Andrew Morton , torvalds@linux-foundation.org, "linux-kernel@vger.kernel.org" , netdev@vger.kernel.org, "alacrityvm-devel@lists.sourceforge.net" To: Gregory Haskins Return-path: In-Reply-To: <4B3334E1.9020401@gmail.com> Sender: kvm-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 12/24/2009 11:31 AM, Gregory Haskins wrote: > On 12/23/09 3:36 PM, Avi Kivity wrote: > >> On 12/23/2009 06:44 PM, Gregory Haskins wrote: >> >>> >>>> - Are a pure software concept >>>> >>>> >>> By design. In fact, I would describe it as "software to software >>> optimized" as opposed to trying to shoehorn into something that was >>> designed as a software-to-hardware interface (and therefore has >>> assumptions about the constraints in that environment that are not >>> applicable in software-only). >>> >>> >>> >> And that's the biggest mistake you can make. >> > Sorry, that is just wrong or you wouldn't have virtio either. > Things are not black and white. I prefer not to have paravirtualization at all. When there is no alternative, I prefer to limit it to the device level and keep it off the bus level. >> Look at Xen, for >> instance. The paravirtualized the fork out of everything that moved in >> order to get x86 virt going. And where are they now? x86_64 syscalls >> are slow since they have to trap to the hypervisor and (partially) flush >> the tlb. With npt or ept capable hosts performance is better for many >> workloads on fullvirt. And paravirt doesn't support Windows. Their >> unsung hero Jeremy is still trying to upstream dom0 Xen support. And >> they get to support it forever. >> > We are only talking about PV-IO here, so not apples to apples to what > Xen is going through. > The same principles apply. >> VMware stuck with the hardware defined interfaces. Sure they had to >> implement binary translation to get there, but as a result, they only >> have to support one interface, all guests support it, and they can drop >> it on newer hosts where it doesn't give them anything. >> > Again, you are confusing PV-IO. Not relevant here. Afaict, vmware, > kvm, xen, etc, all still do PV-IO and likely will for the foreseeable > future. > They're all doing it very differently: - pure emulation (qemu e1000, etc.) - pci device (vmware, virtio/pci) - paravirt bus bridged through a pci device (Xen hvm, Hyper-V (I think), venet/vbus) - paravirt bus (Xen pv, early vbus, virtio/lguest, virtio/s390) The higher you are up this scale the easier things are, so once you get reasonable performance there is no need to descend further. -- error compiling committee.c: too many arguments to function