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

Tony Krowiak
2018-07-02T15:56:03Z

On 06/29/2018 05:11 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@de.ibm.com>
> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
> arch/s390/include/uapi/asm/kvm.h | 1 +
> arch/s390/kvm/kvm-s390.c | 8 ++++++++
> arch/s390/tools/gen_facilities.c | 3 +++
> 3 files changed, 12 insertions(+), 0 deletions(-)
>
> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
> index 4cdaa55..a580dec 100644
> --- a/arch/s390/include/uapi/asm/kvm.h
> +++ b/arch/s390/include/uapi/asm/kvm.h
> @@ -130,6 +130,7 @@ struct kvm_s390_vm_cpu_machine {
> #define KVM_S390_VM_CPU_FEAT_PFMFI 11
> #define KVM_S390_VM_CPU_FEAT_SIGPIF 12
> #define KVM_S390_VM_CPU_FEAT_KSS 13
> +#define KVM_S390_VM_CPU_FEAT_AP 14
> struct kvm_s390_vm_cpu_feat {
> __u64 feat[16];
> };
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 3b7a515..d2208d4 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -40,6 +40,7 @@
> #include <asm/sclp.h>
> #include <asm/cpacf.h>
> #include <asm/timex.h>
> +#include <asm/ap.h>
> #include "kvm-s390.h"
> #include "gaccess.h"
>
> @@ -366,6 +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
> + */
> + 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..e0e2c19 100644
> --- a/arch/s390/tools/gen_facilities.c
> +++ b/arch/s390/tools/gen_facilities.c
> @@ -106,6 +106,9 @@ struct facility_def {
>
> .name = "FACILITIES_KVM_CPUMODEL",
> .bits = (int[]){
> + 12, /* AP Query Configuration Information */
> + 15, /* AP Facilities Test */
> + 156, /* Execution Token facility */

Oops. This last one is an error, the result of a faulty merge with the
latest
code base.

> -1 /* END */
> }
> },