Chris Wright wrote: > * Anthony Liguori (aliguori@xxxxxxxxxx) wrote: > >> Chris Wright wrote: >> >>> Xen also provides support for running directly on native hardware. >>> >> Can someone elaborate on this? Does this mean a Xen guest can run on >> bare metal? >> > > Yes. See the Xen code for running the kernel in ring0 with Xen > (supervisor_mode_kenel). The hypercall_page is conditionally filled > with hypercall traps or direct calls basically. > Cool! I didn't realize the supervisor_mode_kernel code was in the Xen tree code already. Regards, Anthony Liguori >> Is there code available to make this work (it doesn't seem contained in >> this patchset)? Has any performance analysis been done? >> > > I don't have any numbers. > > >> The numbers that have been posted with the VMI patches suggest that some >> rather tricky stuff is required to achieve native performance when >> running a guest on bare metal. If this is not the case, it would be >> very interesting to know because it seems to be the hairiest part of the >> VMI patches. >> > > It is a hairy part of VMI. They've done a nice job of handling the > native case, and have interseting plans for improving the non-native > case (inline where possible). One of the differences is things that > don't actually require hypercalls are already inline w/ Xen. So it's > conceivable that the performance hit is smaller than what VMI found > without carefully inlining native code. > > >> Otherwise, if we want to support Xen guests on bare metal, it seems we >> would have to change things in the subarch code a bit to do something >> similar to VMI. >> > > It's a different approach. > > thanks, > -chris >
