On Wed, May 16, 2018 at 02:44:24PM +0200, Paolo Bonzini wrote: > On 12/05/2018 00:12, Michael S. Tsirkin wrote: > >> Maybe it's a better idea than overloading an option that is only > >> expected to control a CPUID bit. > > Well -realtime would be a bit confusing in that it enables mlock by > > default. > > Currently, the only suboption of "-realtime" is mlock, which means that > the only three valid uses of it are > > -realtime mlock=on > -realtime mlock=off > -realtime '' > > We can change the default, I think. Only the third would change > meaning, and it's a slightly crazy way to use the option. > > > From pure API point of view, hint-dedicated looks good since > > it seems to say "optimize for a dedicated host CPU" and > > it's a hint in that guests keep working if you violate this > > slightly once in a while. > > > > But I agree there's a problem: right now "kvm-" means "KVM PV" > > as opposed to e.g. HV enlightened gusts. > > So if you enable hyperv and also want to disable halt existing, > > what then? What should kvm-hint-dedicated=on do? > > kvm-hint-dedicated=on only sets the CPUID bit, which Linux for example > uses that to disable pv spinlocks. "-realtime dedicated-cpus=on" only > disables the vmexits. You can use the two independently. But when would you want to use the two independently? > Thanks, > > Paolo > > > So how about a new hint-dedicated=on cpu flag? We can have that set > > kvm-hint-dedicated if kvm PV is enabled. > >
