Comment 5 for bug 1692450

------- Comment From <email address hidden> 2017-06-14 08:48 EDT-------
Hi Christian,

This is QEMU 2.11 and linux 4.13 at minimum. So definitely not a Ubuntu 17.10 thing. This is targeted for Ubuntu 18.04.

------- Comment From <email address hidden> 2017-06-14 08:57 EDT-------
(In reply to comment #6)
> Hi,
> especially for new features I assume that you'll do the testing, but some
> sort of extra info on ...
>
> a) what it does

POWER9 has a new interrupt controller called XIVE (eXternal Interrupt Virtualization Engine). This new interrupt controller will provide considerable performance enhancements for interrupts being routed to guests when compared to the previous interrupt controller, XICS (eXternal Interrupt Controller Specification), used on POWER8 processors.

This feature is about building support for a guest to use the XIVE interrupt controller. If this is not available the guest will continue to use emulated XICS as available on POWER8 guets.

> b) how to use/exploit it as a user

We need a host with a kernel and QEMU with the necessary support to export XIVE directly to the guest, plus a guest kernel that can use XIVE. This combination should be enough to make the guest automatically use XIVE. This can be easily checked in dmesg or /proc/interrupts.

> c) implications/regressions

If XIVE is not working the guest will use XICS. This can be checked in dmesg and /proc/interrupts. If no interrupt controller is working this will be easily noticed because the guest will not boot.

> d) HW constraints (min HW level, FW, ...)

This needs POWER9 hardware.