Comment 9 for bug 1920784

You need a kernel with a the following fix for POWER9:

commit 25edcc50d76c834479d11fcc7de46f3da4d95121
Author: Fabiano Rosas <email address hidden>
Date: Thu Feb 4 17:05:17 2021 -0300

    KVM: PPC: Book3S HV: Save and restore FSCR in the P9 path

    The Facility Status and Control Register is a privileged SPR that
    defines the availability of some features in problem state. Since it
    can be written by the guest, we must restore it to the previous host
    value after guest exit.

    This restoration is currently done by taking the value from
    current->thread.fscr, which in the P9 path is not enough anymore
    because the guest could context switch the QEMU thread, causing the
    guest-current value to be saved into the thread struct.

    The above situation manifested when running a QEMU linked against a
    libc with System Call Vectored support, which causes scv
    instructions to be run by QEMU early during the guest boot (during
    SLOF), at which point the FSCR is 0 due to guest entry. After a few
    scv calls (1 to a couple hundred), the context switching happens and
    the QEMU thread runs with the guest value, resulting in a Facility
    Unavailable interrupt.

    This patch saves and restores the host value of FSCR in the inner
    guest entry loop in a way independent of current->thread.fscr. The old
    way of doing it is still kept in place because it works for the old
    entry path.

    Signed-off-by: Fabiano Rosas <email address hidden>
    Signed-off-by: Paul Mackerras <email address hidden>