From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:48630) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gkRGz-0002BN-Hh for qemu-devel@nongnu.org; Fri, 18 Jan 2019 05:21:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gkRGt-0007Te-U8 for qemu-devel@nongnu.org; Fri, 18 Jan 2019 05:21:13 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34876) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gkRGt-0007TC-OC for qemu-devel@nongnu.org; Fri, 18 Jan 2019 05:21:07 -0500 Date: Fri, 18 Jan 2019 10:21:02 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20190118102102.GH20660@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20190118100159.GA2483@work-vm> <8f0f7339-5f47-46d0-20a9-343badad4d0f@redhat.com> <20190118101633.GC2146@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190118101633.GC2146@work-vm> Subject: Re: [Qemu-devel] Live migration from Qemu 2.12 hosts to Qemu 3.2 hosts, with VMX flag enabled in the guest? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: Paolo Bonzini , Mark Mielke , qemu-devel@nongnu.org, christian.ehrhardt@canonical.com On Fri, Jan 18, 2019 at 10:16:34AM +0000, Dr. David Alan Gilbert wrote: > * Paolo Bonzini (pbonzini@redhat.com) wrote: > > On 18/01/19 11:02, Dr. David Alan Gilbert wrote: > > >> > > >> It fails if the flag is set, rather than if any nested virtualization has > > >> been used before. > > >> > > >> I'm concerned I will end up with a requirement for *all* guests to be > > >> restarted in order to migrate them to the new hosts, rather than just the > > >> ones that would have a problem. > > > I think you should be able to migrate from 2.12->3.1 like this, but > > > you'd hit the problem when you then try and migrate again between your > > > new QEMUs. > > > > > > I guess we could modify it to wire it to machine type, so that > > > older machine types didn't block. > > > > That would also be wrong. The old machine types _could_ be using KVM > > and they have no way to block the live migration. > > > > The solution is to restart the VM using "-cpu host,-vmx". > > The problem as Christian explained in that thread is that it was common > for them to start VMs with vmx enabled but for people not to use it > on most of the VMs, so we break migration for most VMs even though most > don't use it. > > It might not be robust, but it worked for a lot of people most of the > time. Yes, this is exactly why I said we should make the migration blocker be conditional on any L2 guest having been started. I vaguely recall someone saying there wasn't any way to detect this situation from QEMU though ? Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|