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.
A user should never have to specify and accelerator option IMHO.
Regards,
Anthony Liguori
Alex
