Rusty Russell wrote: > On Tue, 2007-05-29 at 17:00 +0300, Avi Kivity wrote: > >> Anthony Liguori wrote: >> >>> Avi Kivity wrote: >>> >>>> I think we should aim for a full direct paging implementation, where >>>> the cr3 cache is just the cherry on top that makes context switches >>>> proceed at native speed. Jun has a paper on it for OLS and I hope >>>> patches too. >>>> >>> That's a bit more ambitious than I was thinking. I would be very >>> happy with a pv timer, interrupt controller, and some basic CPU >>> optimizations. I'm still not convinced the perf benefits of direct >>> paging justify the annoyances that come with it (guests being aware of >>> pfns). >>> >> I thought that with paravirt_ops, all the awareness is limited to the >> paravirt implementation, and nothing in the core kernel is actually >> aware of host pfns. >> > > It is, but now you've broken the abstraction you get other messes. You > can no longer simply swap out pages behind the guest's back, copy on > write or combine identical pages or other tricks without synchronizing > with the guest. > >
These are good points. > It can be done, Maybe we'll get something from the s390 port. > but it's not clear to me that verifying PTEs is that > much faster than shadowing them if you're prepared to be that invasive > in the guest anyway. > This can probably be measured on Xen which can switch from direct to shadow mode on runtime. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
