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SubjectRe: [PATCH v2 04/15] KVM: s390: CPU model support for AP virtualization
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On 27.02.2018 15:28, 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 the
> AP facilities are installed on the KVM guest. This
> feature will be enabled by the kernel only if the AP
> facilities are installed on the linux host. This feature
> must be specifically turned on for the KVM guest from
> userspace to allow guest access to AP devices installed
> on the linux host.
>
> 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.
>
> 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.
>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
> ---
> arch/s390/include/uapi/asm/kvm.h | 1 +
> arch/s390/kvm/kvm-s390.c | 4 ++++
> arch/s390/tools/gen_facilities.c | 2 ++
> 3 files changed, 7 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 de1e299..c68ca86 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -347,6 +347,10 @@ static void kvm_s390_cpu_feat_init(void)
>
> if (MACHINE_HAS_ESOP)
> allow_cpu_feat(KVM_S390_VM_CPU_FEAT_ESOP);
> +
> + if (ap_instructions_installed()) /* AP instructions installed on host */
> + allow_cpu_feat(KVM_S390_VM_CPU_FEAT_AP);

Don't we have a SIE specific AP feature? So is it true, that once we
have AP instructions, we are allowed to use them for SIE? Isn't there a
"AP interpretation facility" or anything like that? (that unlocks ECA_APIE)

> +
> /*
> * 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 */
> }
> },
>

So only if this feature is enabled, we later on allow to
kvm_ap_enable_ie_mode, right?

So basically, without this feature:

1. We will never set the execution control ECA_APIE.
2. The masks will always be 0.

Which also results in VSIE never having masks set.


--

Thanks,

David / dhildenb

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