[libvirt] [PATCH] cpu_ppc64: Add support for host-model on POWER9

[Andrea Bolognani]

On Thu, 2017-06-08 at 18:40 +0200, Andrea Bolognani wrote:
> Yeah, I've been looking at downstream. I'll try again with
> upstream and file bugs as needed.

Okay, I've tried again with upstream QEMU master (with your
CPU compatibility patches applied on top), here are the
results for both POWER8 and POWER9.


<nothing>
=========

  * POWER8 (architected)
  * POWER9 (raw)

-cpu POWER8
===========

  * POWER8 (architected)
  * qemu-system-ppc64: Register sync failed...
    If you're using kvm-hv.ko, only "-cpu host" is possible
    kvm_init_vcpu failed: Invalid argument

-cpu POWER9
===========

  * qemu-system-ppc64: Register sync failed...
    If you're using kvm-hv.ko, only "-cpu host" is possible
    kvm_init_vcpu failed: Invalid argument
  * qemu-system-ppc64: Register sync failed...
    If you're using kvm-hv.ko, only "-cpu host" is possible
    kvm_init_vcpu failed: Invalid argument

-cpu host
=========

  * POWER8 (architected)
  * POWER9 (raw)

-cpu host,compat=power8
=======================

  * POWER8 (architected)
  * Unexpected error in ppc_set_compat() at target/ppc/compat.c:135:
    qemu-system-ppc64: Compatibility PVR 0x0f000004 not valid for CPU
    Aborted

-cpu host,compat=power9
=======================

  * Unexpected error in ppc_set_compat() at target/ppc/compat.c:135:
    qemu-system-ppc64: Compatibility PVR 0x0f000005 not valid for CPU
    Aborted
  * Unexpected error in ppc_set_compat() at target/ppc/compat.c:135:
    qemu-system-ppc64: Compatibility PVR 0x0f000005 not valid for CPU
    Aborted


AIUI, the fact that POWER9 is using raw mode rather than
architected mode for all cases where the guest actually
manages to boot is because compatibility modes are not enabled
for early silicon; this is consistent with QEMU refusing to
use the compatibility modes when explicitly asked to do so.

However, the fact that '-cpu POWER9' can't be used on the
POWER9 machine seems like a genuine bug. Even on POWER8, the
error message is pretty misleading.

Last but not least, using an unsupported compatibility mode
results in QEMU abort()ing, which seems a bit excessive for
a very reasonable guest configuration error.


Do you want me to go ahead and file bugs for the last two
items?

-- 
Andrea Bolognani / Red Hat / Virtualization