Re: [RFC 4/5] s390x/cpumodel: enable AP facilities for guest

David Hildenbrand
2017-11-14T16:23:39Z

On 14.11.2017 16:11, Cornelia Huck wrote:
> On Thu, 26 Oct 2017 11:54:53 -0400
> Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:
>
>> Sets up the following STFLE bits to enable the specified AP
>> facilities for the guest VM:
>> * STFLE.12: Enables the AP Query Configuration Information
>> facility. The AP bus running in the guest uses
>> the information returned from this instruction
>> to configure AP adapters and domains for the
>> guest machine.
>> * STFLE.15: Enables the AP Special Command facility. The AP
>> bus running in the guest sets the T bit in
>> register 0 for the PQAP(TAPQ) instruction when
>> scanning for AP devices if this facility is
>> installed.
>>
>> These facilities are required in order for the AP bus running on
>> the KVM guest to function properly.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
>> ---
>> target/s390x/cpu_features.c | 2 ++
>> target/s390x/cpu_features_def.h | 2 ++
>> target/s390x/gen-features.c | 4 ++++
>> 3 files changed, 8 insertions(+), 0 deletions(-)
>>
>> diff --git a/target/s390x/cpu_features.c b/target/s390x/cpu_features.c
>> index 31a4676..63f002c 100644
>> --- a/target/s390x/cpu_features.c
>> +++ b/target/s390x/cpu_features.c
>> @@ -36,8 +36,10 @@ static const S390FeatDef s390_features[] = {
>> FEAT_INIT("srs", S390_FEAT_TYPE_STFL, 9, "Sense-running-status facility"),
>> FEAT_INIT("csske", S390_FEAT_TYPE_STFL, 10, "Conditional-SSKE facility"),
>> FEAT_INIT("ctop", S390_FEAT_TYPE_STFL, 11, "Configuration-topology facility"),
>> + FEAT_INIT("apqci", S390_FEAT_TYPE_STFL, 12, "Query Adjunct Processor Configuration facility"),
>> FEAT_INIT("ipter", S390_FEAT_TYPE_STFL, 13, "IPTE-range facility"),
>> FEAT_INIT("nonqks", S390_FEAT_TYPE_STFL, 14, "Nonquiescing key-setting facility"),
>> + FEAT_INIT("apsc", S390_FEAT_TYPE_STFL, 15, "Adjunct Processor Special Command facility"),
>
> Are there any interdependencies for those feature bits?

And just as a side node, CPU features should only be exposed once
migration support is fully in place (and usually bound to the flag for
compat handling).

(haven't had time yet to have a closer look, so just as a general comment)

--

Thanks,

David / dhildenb