On Wed, Apr 30, 2014 at 02:14:00PM -0300, Marcelo Tosatti wrote: > On Wed, Apr 30, 2014 at 10:44:33AM +0200, Paolo Bonzini wrote: > > Il 30/04/2014 03:11, Marcelo Tosatti ha scritto: > > > On Tue, Apr 29, 2014 at 06:17:17PM -0300, Eduardo Habkost wrote: > > >> KVM never supported the MONITOR flag so it doesn't make sense to have it > > >> enabled by default when KVM is enabled. > > >> > > >> The rationale here is similar to the cases where it makes sense to have > > >> a feature enabled by default on all CPU models when on KVM mode (e.g. > > >> x2apic). In this case we are having a feature disabled by default for > > >> the same reasons. > > >> > > >> In this case we don't need machine-type compat code because it is > > >> currently impossible to run a KVM VM with the MONITOR flag set. > > >> > > >> Signed-off-by: Eduardo Habkost <ehabk...@redhat.com> > > > > > > Why relying on the kernel filtering is not sufficient ? > > > > Because that would break "-cpu ...,enforce". In fact many old models > > are currently broken because they were never tested with "-cpu > > ...,enforce". For example: > > Isnt the point of enforce to fail if the provided feature cannot be > exposed ? > > That is, if the emulated CPU specifies MONITOR, and KVM can't provide > it, then enforce should fail initialization?
Exactly. But why should we have a CPU that is will never run, by default? The point here is to have reasonable defaults. -- Eduardo
