On 2012-05-22 13:12, Erik Rull wrote: > Jan Kiszka wrote: >> On 2012-05-22 07:34, Jan Kiszka wrote: >>> On 2012-05-22 07:04, Stefan Hajnoczi wrote: >>>> On Mon, May 21, 2012 at 5:54 PM, Erik Rull<webmas...@rdsoftware.de> wrote: >>>>> is there a summary existing that shows up the rough or actual differences >>>>> between qemu --enable-kvm and qemu-kvm? I tested both versions with the >>>>> same >>>>> compile and start options, the CPU performance results are identical, only >>>>> the bootup time of my guest system with qemu-kvm seemed to be a bit faster >>>>> (not measured, it just feeled so). >>> >>> Current upstream does not enable the in-kernel irqchip of KVM by >>> default. This should explain the difference in boot-up times. Try >>> "-machine accel=kvm,kernel_irqchip=on". But the default will be on, just >>> like in qemu-kvm, once [1] is merged. >>> >>>> >>>> For production KVM instances I think it still makes sense to use >>>> qemu-kvm packages from your distro or qemu-kvm upstream source. >>>> >>>> Jan Kiszka has reduced the delta between qemu.git and qemu-kvm.git to >>>> the point where I think the list of differences is rather small - >>>> maybe PCI passthrough stuff, irqfd for vhost-net (which is now also >>>> being upstreamed into qemu.git), and a few other things I don't know >>>> of. >>> >>> Right, the list of differences is dramatically shrinking. As stated in >>> [2], soon only PCI passthrough and legacy interface dependencies on >>> qemu-kvm will be the remaining reasons to use it. If we are lucky, PCI >>> passthrough will also make it into upstream for QEMU 1.2, we are working >>> on this. >>> >>>> >>>> For development most patches should be against qemu.git unless they >>>> have a dependency on qemu-kvm.git code. >>> >>> Yes, unless you are working on the upstream merge itself, there is >>> practically no reason anymore to develop against qemu-kvm directly. >>> >>> Jan >>> >>> [1] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/91171 >>> [2] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/91026 >>> >> >> I've added some more details on this to the QEMU wiki, see >> http://wiki.qemu.org/KVM. >> >> BTW, if someone could have a look at the VGA diffs and resolve them, >> that would be great. Gerd, what's the state of switching the BIOS? >> >> Jan >> > > Hi all, > > thanks a lot! > > I don't use PCI device assignment - so the missing irqchip-default-option > should be the biggest difference between these two versions, right?
And the lacking MSI support when irqchip is on. If that matters depends on your workload. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux