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SubjectRe: [PATCH v8 21/22] KVM: s390: CPU model support for AP virtualization
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On 08.08.2018 16:44, Tony Krowiak wrote:
> From: Tony Krowiak <akrowiak@linux.ibm.com>
>
> 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.

Could it happen on real HW (not frankenstein CPU models), that

!AP, but STFL 12 or 15 are indicated?

>
> 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 for the virtual
> machine. This is a limitation of the Linux AP bus.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
> Tested-by: Michael Mueller <mimu@linux.ibm.com>
> Tested-by: Farhan Ali <alifm@linux.ibm.com>
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> arch/s390/kvm/kvm-s390.c | 7 +++++++
> arch/s390/tools/gen_facilities.c | 2 ++
> 2 files changed, 9 insertions(+), 0 deletions(-)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 9203f0b..7d4fe9b 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
> + */

Make this a one-line comment, please.

> + 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 90a8c9e..a52290b 100644
> --- a/arch/s390/tools/gen_facilities.c
> +++ b/arch/s390/tools/gen_facilities.c
> @@ -106,6 +106,8 @@ struct facility_def {
>
> .name = "FACILITIES_KVM_CPUMODEL",
> .bits = (int[]){
> + 12, /* AP Query Configuration Information */
> + 15, /* AP Facilities Test */
> -1 /* END */
> }
> },
>


--

Thanks,

David / dhildenb

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