On Thu, 26 Jul 2018 21:54:28 +0200
Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote:
> From: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
>
> 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.
What is "the AP bus running on the guest"? The AP bus is a Linux
construct, and while we only care about Linux guests right now for AP,
I would not word it that way.
"If this facility is not set for the KVM guest, then only
APQNs with an APQI less than 16 will be used by a Linux
guest regardless of the matrix configuration for the virtual
machine. This is a limitation of the Linux AP bus."
?
>
> 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.
Same here.
>
> Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
> Tested-by: Michael Mueller <mimu@xxxxxxxxxxxxx>
> Tested-by: Farhan Ali <alifm@xxxxxxxxxxxxx>
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
> arch/s390/kvm/kvm-s390.c | 7 +++++++
> arch/s390/tools/gen_facilities.c | 2 ++
> 2 files changed, 9 insertions(+)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 738b090fcf54..0eecc9ddb364 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -367,6 +367,13 @@ static void kvm_s390_cpu_feat_init(void)
>
> if (MACHINE_HAS_ESOP)
> allow_cpu_feat(KVM_S390_VM_CPU_FEAT_ESOP);
> +
> + /*
> + * Check if AP instructions installed on host
/* check whether AP instructions are installed on host */
?
> + */
> + if (ap_instructions_available() == 0)
> + allow_cpu_feat(KVM_S390_VM_CPU_FEAT_AP);
> +
> /*
> * We need SIE support, ESOP (PROT_READ protection for gmap_shadow),
> * 64bit SCAO (SCA passthrough) and IDTE (for gmap_shadow unshadowing).
> diff --git a/arch/s390/tools/gen_facilities.c b/arch/s390/tools/gen_facilities.c
> index 90a8c9e84ca6..a52290bb8ad5 100644
> --- a/arch/s390/tools/gen_facilities.c
> +++ b/arch/s390/tools/gen_facilities.c
> @@ -106,6 +106,8 @@ static struct facility_def facility_defs[] = {
>
> .name = "FACILITIES_KVM_CPUMODEL",
> .bits = (int[]){
> + 12, /* AP Query Configuration Information */
> + 15, /* AP Facilities Test */
> -1 /* END */
> }
> },
Other than the nits above, patch looks good to me.
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