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

[Tony Krowiak]

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@xxxxxxxxxx>
> Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
> Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> ---
>   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 */
>   		}
>   	},