From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH 05/11] KVM: s390: Support Configuration z/Architecture
 Mode
Date: Mon, 28 Aug 2017 21:41:04 +0200
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To: Christian Borntraeger <borntraeger@de.ibm.com>, Cornelia Huck <cohuck@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>, KVM <kvm@vger.kernel.org>, linux-s390 <linux-s390@vger.kernel.org>, "Jason J. Herne" <jjherne@linux.vnet.ibm.com>
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On 28.08.2017 21:35, Christian Borntraeger wrote:
> 
> 
> On 08/28/2017 09:27 PM, David Hildenbrand wrote:
>>
>>>  		rc = handle_sigp_dst(vcpu, order_code, cpu_addr,
>>> diff --git a/arch/s390/tools/gen_facilities.c b/arch/s390/tools/gen_facilities.c
>>> index 025ea20..181db5b 100644
>>> --- a/arch/s390/tools/gen_facilities.c
>>> +++ b/arch/s390/tools/gen_facilities.c
>>> @@ -80,6 +80,7 @@ static struct facility_def facility_defs[] = {
>>>  			78, /* enhanced-DAT 2 */
>>>  			130, /* instruction-execution-protection */
>>>  			131, /* enhanced-SOP 2 and side-effect */
>>> +			138, /* configuration z/architecture mode (czam) */
>>>  			146, /* msa extension 8 */
>>>  			-1  /* END */
>>>  		}
>>>
>>
>> Thinking about it, this should be the right thing to do instead of the
>> last hunk:
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 84c069afc02f..39115f5a38df 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -1927,6 +1927,10 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned
>> long type)
>>         memcpy(kvm->arch.model.fac_list, kvm->arch.model.fac_mask,
>>                S390_ARCH_FAC_LIST_SIZE_BYTE);
>>
>> +       /* we are always in CZAM mode - even on pre z14 machines */
>> +       set_kvm_facility(kvm->arch.model.fac_mask, 138);
>> +       set_kvm_facility(kvm->arch.model.fac_list, 138);
>> +       /* we emulate STHYI in kvm */
>>         set_kvm_facility(kvm->arch.model.fac_mask, 74);
>>         set_kvm_facility(kvm->arch.model.fac_list, 74);
>>         if (MACHINE_HAS_TLB_GUEST) {
>>
>> That would produce consistent results for very old QEMU.
>>
> 
> This should be identical as the initial fac_list is populated from the fac_mask,
> which is populated by the facility_defs structure.
> 
> [..]
>        /* Populate the facility list initially. */
>         kvm->arch.model.fac_list = kvm->arch.sie_page2->fac_list;
> ---->   memcpy(kvm->arch.model.fac_list, kvm->arch.model.fac_mask,
>                S390_ARCH_FAC_LIST_SIZE_BYTE);
> 
> [,..]
> 

This would keep it unset on e.g. a z13, no? (that's why I added the
comment regarding z14)


By always enabling it we would behave exactly like QEMU.

-- 

Thanks,

David