On Fri, 23 May 2014, Paul Durrant wrote: > > -----Original Message----- > > From: Stefano Stabellini [mailto:stefano.stabell...@eu.citrix.com] > > Sent: 22 May 2014 14:57 > > To: Gerd Hoffmann > > Cc: Paolo Bonzini; Stefano Stabellini; Paul Durrant; qemu-devel@nongnu.org; > > Anthony Liguori; m...@redhat.com > > Subject: Re: [PATCH] xen: make xen-platform a default device > > > > On Thu, 22 May 2014, Gerd Hoffmann wrote: > > > > > Given that libxl always passes -nodefaults to QEMU, this patch is > > > > > going > > > > > to effectively disable xen_platform_pci for all Xen users. It is not a > > > > > good idea. With the patch applied a Xen user would have no way to > > enable > > > > > xen_platform_pci except for passing some magic command line runes > > via > > > > > device_model_args_hvm. > > > > > > > > In fact this code only runs for "-M xenfv". If you use "-M pc", the > > > > xen-platform device has to be added manually. Perhaps it would be > > > > worthwhile to do the opposite, i.e. add the xen-platform device to "-M > > > > pc" if not using -nodefaults. > > > > > > /me looks at the code. Yes, all the differences between xenfv and pc > > > machine types are guarded by if (xen_enabled()) these days, except for > > > adding the platform device. > > > > > > So using the pc machine type should just work on xen, and give you a > > > machine without the platform device. So it can be added via -device, at > > > any slot, if needed. No need to patch qemu at all. Adding or not > > > adding xen-platform can easily handled by libxl then, depending on the > > > xen_platform_pci switch in the config file. > > > > I agree. Changing libxl to always use -M pc and using -device to add > > xen-platform when needed sounds like the best option. > > Really? You opposed this before: > > http://lists.xen.org/archives/html/xen-devel/2013-06/msg01946.html > > stating that you wanted a mechanism to query the running version of QEMU > before choosing the machine type.
Many QEMU releases have been made since then. I feel more comfortable with using -M pc, especially given the alternatives that have been proposed. Of course having a mechanism to query the running version of QEMU would still be the safest solution.
