On 09/07/2012 09:13 AM, Daniel P. Berrange wrote:
On Fri, Sep 07, 2012 at 02:51:00PM +0200, Peter Krempa wrote:
When setting processor count for a domain using the API libvirt enforced a maximum processor count that was determined using an IOCTL on /dev/kvm. Unfortunately this value isn't representative enough and qemu happily accepts and starts with values greater than the reported value.
Really ? If KVM is accepting a greater vCPU count than it reports via /dev/kvm, then we should fix the latter
Why? We already allow oversubscription (you can run 3 guests with 1 vcpu each on a 2-cpu machine); we also allow pinning a 2-vcpu guest to 1 host cpu; so why can't we allow oversubscription from within a single VM? Sure, performance will be lousier, but that doesn't mean the request is invalid. -- Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org