On Tue, 16 Nov 2010, Anthony Liguori wrote: > On 11/16/2010 11:24 AM, Alexander Graf wrote: > > On 16.11.2010, at 18:20, Anthony Liguori wrote: > > > > > >> On 11/16/2010 10:59 AM, Alexander Graf wrote: > >> > >>> > >>>> Surely, only if it is running on a Xen Dom0. If you use -M xenpv on a KVM > >>>> host, then -M xenpv should imply -machine accel=kvm (ie it would be using > >>>> xenner) > >>>> > >>>> > >>> Actually, it should imply -machine accel=kvm,tcg :). Accelerators really > >>> are not a machine property. In an ideal world, -M pc would just work with > >>> xen hvm if -accel xen is given. > >>> > >>> > >> No, an accelerator is both a CPU selection and a machine characteristic. > >> For KVM, we overload -cpu to modify both the KVM CPU and the TCG CPU both > >> this won't work with accel=xen. We probably shouldn't do this with KVM > >> either because there's a significant different between trying to do cpuid > >> masking with KVM and modifying the TCG cpu emulation support. > >> > >> Both KVM and Xen have other impacts on the platform devices though. KVM > >> does not support SMM so it disables that in the i440fx. KVM prefers to > >> use it's own in-kernel local APIC (and IOAPIC). That makes it a property > >> of the machine. > >> > > So you're saying the machine should define an accel mask of accels it > > supports? > > > > However all this ends up internally, giving the user an easy option to > > choose accels would still be nice. Users don't use -device or -machine. > > They want shortcuts :). > > > > User's want things to just work. > > That's why -M xenpv should imply -machine accel=xen.
Actually, it works like that for qemu-xen, we just specify -M xenpv, and we don't have any --enable-xen or other -accel xen. > A user should never have to specify and accelerator option IMHO. -- Anthony PERARD
