Re: [PATCH v2] KVM: s390: provide a capability for AIS state migration

David Hildenbrand
2017-11-09T14:57:24Z

On 09.11.2017 10:53, Cornelia Huck wrote:
> On Thu, 9 Nov 2017 10:47:23 +0100
> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
>
>> The AIS capability was introduced in 4.12, while the interface to
>> migrate the state was added in 4.13. Unfortunately it is not possible
>> for userspace to detect the migration capability without creating a flic
>> kvm device. As in QEMU the the cpu model detection runs on the "none"
>
> s/the the/the/
>
>> machine this will result in cpu model issues regarding the "ais"
>> capability.
>>
>> To get the "ais" capability properly let's add a new KVM capability that
>> tells userspace that AIS states can be migrated.
>>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> ---
>> Documentation/virtual/kvm/api.txt | 8 ++++++++
>> Documentation/virtual/kvm/devices/s390_flic.txt | 2 ++
>> arch/s390/kvm/kvm-s390.c | 1 +
>> include/uapi/linux/kvm.h | 1 +
>> 4 files changed, 12 insertions(+)
>>
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index e63a35f..51553ba 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -4347,3 +4347,11 @@ This capability indicates that userspace can load HV_X64_MSR_VP_INDEX msr. Its
>> value is used to denote the target vcpu for a SynIC interrupt. For
>> compatibilty, KVM initializes this msr to KVM's internal vcpu index. When this
>> capability is absent, userspace can still query this msr's value.
>> +
>> +8.13 KVM_CAP_S390_AIS_MIGRATION
>> +
>> +Architectures: s390
>> +Parameters: none
>> +
>> +This capability indicates if the flic device will be able to get/set the
>> +AIS states for migration via the KVM_DEV_FLIC_AISM_ALL attribute.
>
> "and allows to discover this without having to create a flic device."
>
>> diff --git a/Documentation/virtual/kvm/devices/s390_flic.txt b/Documentation/virtual/kvm/devices/s390_flic.txt
>> index 27ad53c..a4e20a0 100644
>> --- a/Documentation/virtual/kvm/devices/s390_flic.txt
>> +++ b/Documentation/virtual/kvm/devices/s390_flic.txt
>> @@ -151,6 +151,8 @@ struct kvm_s390_ais_all {
>> to an ISC (MSB0 bit 0 to ISC 0 and so on). The combination of simm bit and
>> nimm bit presents AIS mode for a ISC.
>>
>> + KVM_DEV_FLIC_AISM_ALL is indicated by KVM_CAP_S390_AIS_MIGRATION.
>> +
>> Note: The KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR device ioctls executed on
>> FLIC with an unknown group or attribute gives the error code EINVAL (instead of
>> ENXIO, as specified in the API documentation). It is not possible to conclude
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index de6a5b7..8f4b655 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -395,6 +395,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>> case KVM_CAP_S390_USER_INSTR0:
>> case KVM_CAP_S390_CMMA_MIGRATION:
>> case KVM_CAP_S390_AIS:
>> + case KVM_CAP_S390_AIS_MIGRATION:
>> r = 1;
>> break;
>> case KVM_CAP_S390_MEM_OP:
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 8388875..b605956 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -930,6 +930,7 @@ struct kvm_ppc_resize_hpt {
>> #define KVM_CAP_PPC_SMT_POSSIBLE 147
>> #define KVM_CAP_HYPERV_SYNIC2 148
>> #define KVM_CAP_HYPERV_VP_INDEX 149
>> +#define KVM_CAP_S390_AIS_MIGRATION 150
>>
>> #ifdef KVM_CAP_IRQ_ROUTING
>>
>
> With the small addition above,
>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>

Looks good to me and avoids trouble we had in qemu.

Reviewed-by: David Hildenbrand <david@redhat.com>

--

Thanks,

David / dhildenb