On Wed, 2008-03-12 at 14:36 -0700, Jeremy Fitzhardinge wrote: > Anthony Liguori wrote: > >> Vp should never happen, since you'd never preserve a V page. And > >> surely it would be Pr -> Sr, since the hypervisor wouldn't push the > >> page to backing store when you change the client state. > >> > > > > You're right, I meant Vp/Pp but they are invalid states. I think one of > > the things that keeps tripping me up is that the host can change both > > the host and guest page states. My initial impression was that the host > > handled the host state and the guest handled the guest state. > > > > Yes. And it seems to me that you get unfortunate outcomes if you have a > Pr->Vz->Vr transition. Vz->Vr cannot happen. This would be a bug in the host. > > I was thinking that it may be useful to know a Ur verses a Uz when > > allocating memory. In this case, you'd rather allocate Ur pages verses > > Uz to avoid the fault. I don't read s390 arch code well, is the host > > state explicit to the guest? > > > > Yes, reusing Ur pages might well be better, but who knows - they've > probably got an instruction which makes Uz cheap... Yes, faulting in a Uz page is cheap on s390. Isn't it a lovely architecture :-) > Stuff like this suggets that both parts of the state are packed > together, and are guest-visible: > > + return (state & ESSA_USTATE_MASK) == ESSA_USTATE_VOLATILE && > + (state & ESSA_CSTATE_MASK) == ESSA_CSTATE_ZERO; > Yes, the return value of the ESSA instruction has both the guest state and the host state. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
