On Thu, Jun 05, 2014 at 06:58:17PM +0200, Alexander Graf wrote: > > On 05.06.14 18:52, Paolo Bonzini wrote: > >Il 05/06/2014 18:45, Alexander Graf ha scritto: > >>>> > >>> > >>>Only if you were using "-cpu somethingThatHasAVX", though, no? > >> > >>Yes. The same argument goes the other way around. I want to use AVX > >>emulation, do "allow-emulation" and suddenly I get MONITOR/MWAIT > >>emulation. > > > >What about: > > > >- letting "-cpu foo,+emulatedfeature" just work > > > >- adding emulated=yes that blindly enables all emulated features > > > >- making "-cpu ...,check" prints a warning for emulated features > >unless emulated=yes > > So: > > -cpu foo,+emulatedFeature just works The problem with this is: * -cpu foo,+emulatedFeature,enforce MUST fail. We don't want to enable emulated/experimental features by accident, even if they appear in the command-line expliclty. * -cpu foo,+emulatedFeature (no "enforce" flag) MUST remove remove the feature and report it on the "filtered-features" property, because that's the only API available for management to check if a feature is not available on GET_SUPPORTED_CPUID. That's why I suggest that the only way to enable emulatedFeature be using "allow-emulation=yes" explicitly on the command-line IN ADDITION to already having the feature included in the CPU model definition or in explicitly in the command-line. (or "allow-experimental-features", or whatever name we choose) > > -cpu foo,+notEmulatedFeature still sets the CPUID bit for that feature That's OK, but (I assume) you mean notEmulatedFeature is on GET_SUPPORTED_CPUID. Detailing the requirements: * "-cpu foo,+SomeFeature" MUST NOT enable SomeFeature unless it is present on GET_SUPPORTED_CPUID. * "-cpu foo,+SomeFeature,enforce" MUST abort if the feature is not present on GET_SUPPORTED_CPUID. * "-cpu foo,+SomeFeature" MUST report SomeFeature on "filtered-features", so management knows the feature is not set on GET_SUPPORTED_CPUID. The items above are already part of the semantics of "-cpu" and if we change it, we risk defeating the whole purpose of GET_EMULATED_CPUID in the first place. > > -cpu foo,check prints warnings for all cpuid bits not in the > "allowed" bitmap. It prints different warnings depending on whether > the bit is in "emulated" or not That part makes sense. And we may also report GET_EMULATED_CPUID features on an "emulated-features" property, so management can get that information in a machine-friendly way. -- Eduardo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
