On 16/06/2016 19:03, David Matlack wrote: > > > If you make the else case the same as svm_handle_external_intr, can we > > > avoid requiring ack-intr-on-exit? > > > > Yes, but the sti/nop/cli would be useless if ack-intr-on-exit is > > available. It's a bit ugly, so I RFCed the bold thing instead. > > Ahh, and handle_external_intr is called on every VM-exit, not just > VM-exits caused by external interrupts. So we'd be doing the > sti/nop/cli quite often. I was thinking we never hit the else case > when the CPU supports ack-intr-on-exit. Actually it's really just aesthetics, because the sti and cli are pretty cheap. It's the pushf/popf that kills performance for kvm_guest_exit. I also thought of just doing a cli/sti around __kvm_guest_exit and calling it a day. Ubuntu 14.04 had kernel 3.13, but the latest hardware enablement kernels are as recent as 4.4. And the most recent released RHEL (7.2) has all the fixes too. Debian Jessie has 3.16.7-ckt25, and all three patches for APICv support have been backported to 3.16.7-ckt11. So they should be there (but I can only check tomorrow). Paolo >> > >> > Are you thinking of some distros in particular that lack nested >> > ack-intr-on-exit? All processors have it as far as I know. > Nope, I just thought it was possible to avoid the requirement. > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
