Re: [PATCH v6 05/21] KVM: s390: CPU model support for AP virtualization

From: Tony Krowiak
Date: Mon Jul 02 2018 - 11:54:40 EST


On 07/02/2018 11:41 AM, Cornelia Huck wrote:
On Mon, 2 Jul 2018 11:37:11 -0400
Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:

On 07/02/2018 10:38 AM, Christian Borntraeger wrote:
On 06/29/2018 11:11 PM, Tony Krowiak wrote:
Introduces a new CPU model feature and two CPU model
facilities to support AP virtualization for KVM guests.

CPU model feature:

The KVM_S390_VM_CPU_FEAT_AP feature indicates that
AP instructions are available on the guest. This
feature will be enabled by the kernel only if the AP
instructions are installed on the linux host. This feature
must be specifically turned on for the KVM guest from
userspace to use the VFIO AP device driver for guest
access to AP devices.

CPU model facilities:

1. AP Query Configuration Information (QCI) facility is installed.

This is indicated by setting facilities bit 12 for
the guest. The kernel will not enable this facility
for the guest if it is not set on the host. This facility
must not be set by userspace if the KVM_S390_VM_CPU_FEAT_AP
feature is not installed.

If this facility is not set for the KVM guest, then only
APQNs with an APQI less than 16 will be available to the
guest regardless of the guest's matrix configuration. This
is a limitation of the AP bus running on the guest.

2. AP Facilities Test facility (APFT) is installed.

This is indicated by setting facilities bit 15 for
the guest. The kernel will not enable this facility for
the guest if it is not set on the host. This facility
must not be set by userspace if the KVM_S390_VM_CPU_FEAT_AP
feature is not installed.

If this facility is not set for the KVM guest, then no
AP devices will be available to the guest regardless of
the guest's matrix configuration. This is a limitation
of the AP bus running under the guest.

Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
I think it probably should be at the end of the series, other than that its good.
If I move this to the end of the series, the very next patch checks the

KVM_S390_VM_CPU_FEAT_AP feature?
Introduce it here, offer it only with the last patch?

I apologize, but I don't know what you mean by this. Are you suggesting this patch
should only include the #define for KVM_S390_VM_CPU_FEAT_AP?