Re: [PATCH v10 25/26] KVM: s390: CPU model support for AP virtualization

David Hildenbrand
2018-09-24T08:33:36Z

On 22/09/2018 01:31, Tony Krowiak wrote:
> On 09/12/2018 03:43 PM, 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.
>>
>> 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.
>>
>> 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>
>> Reviewed-by: David Hildenbrand <david@redhat.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 | 5 +++++
>> arch/s390/tools/gen_facilities.c | 2 ++
>> 2 files changed, 7 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 286c2e0..f0b8e2a 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -371,6 +371,11 @@ 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())
>> + 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 0c85aed..fd788e0 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 */
>> 156, /* etoken facility */
>> -1 /* END */
>> }
>>
>
> The fixup! patch below modifies this patch (25/26) to illustrate how
> David's recommendation will be implemented for v11 of the series. It
> is one of three fixup! patches (the other two are in responses to
> 03/26 and 11/26) included to generate discussion in v10 rather than
> waiting until v11 for comments.
>
> -----------------------------------8<-----------------------------------
>
> From: Tony Krowiak <akrowiak@linux.ibm.com>
> Date: Thu, 20 Sep 2018 13:28:07 -0400
> Subject: [FIXUP v10] fixup!: KVM: s390: CPU model support for AP
> virtualization
>
> ---
> arch/s390/kvm/kvm-s390.c | 4 ----
> 1 files changed, 0 insertions(+), 4 deletions(-)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index a3a7cd9..ff38251 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -372,10 +372,6 @@ 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())
> - 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).
>

Yes, looks sane.

--

Thanks,

David / dhildenb