On Wed, Nov 29, 2017 at 02:20:34AM +0200, Michael S. Tsirkin wrote: > On Wed, Nov 29, 2017 at 01:07:32AM +0100, Paolo Bonzini wrote: > > On 28/11/2017 15:08, Michael S. Tsirkin wrote: > > > I think guests still want some way to halt when > > > giving up CPU for a long time. > > > > > > If you are not worried about guests entering low power states, > > > then you only need MWAIT and maybe PAUSE. > > > > > > HLT within guest only makes sense if you do not want to > > > allow guest to enter power state. > > > > > > If you don't exit on any of these, you want some other way > > > to actually halt the VCPU. > > > > If you want to do something in userspace, send a signal. Otherwise, it > > doesn't really matter (if you have a dedicated physical CPU) whether the > > task is runnable or not, as long as the CPU isn't in C0. > > > > Paolo > > If VCPU wants to give up its timeslice, how is it supposed to do it > if all exits are blocked? All this doesn't mean the patch can't be applied. But I think it would be handy to add another way to exit to host and stop until an interrupt. E.g. an access to a special address could do it. > -- > MST
