Alex Graf has added support for KVM acceleration of the pseries machine, using his Book3S-PR KVM variant, which runs the guest in userspace, emulating supervisor operations. Recent kernels now have the Book3S-HV KVM variant which uses the hardware hypervisor features of recent POWER CPUs. Alex's changes to qemu are enough to get qemu working roughly with Book3S-HV, but taking full advantage of this mode needs more work. This patch series makes a start on better exploiting Book3S-HV.
Even with these patches, qemu won't quite be able to run on a current Book3S-HV KVM kernel. That's because current Book3S-HV requires guest memory to be backed by hugepages, but qemu refuses to use hugepages for guest memory unless KVM advertises CAP_SYNC_MMU, which Book3S-HV does not currently do. We're working on improvements to the KVM code which will implement CAP_SYNC_MMU and allow smallpage backing of guests, but they're not there yet. So, in order to test Book3S-HV for now you need to either: * Hack the host kernel to lie and advertise CAP_SYNC_MMU even though it doesn't really implement it. or * Hack qemu so it does not check for CAP_SYNC_MMU when the -mem-path option is used. Bot approaches are ugly and unsafe, but it seems we can generally get away with it in practice. Obviously this is only an interim hack until the proper CAP_SYNC_MMU support is ready.
