Re: [RFC 31/37] KVM: s390: protvirt: Add diag 308 subcode 8 - 10 handling

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On 11/15/19 11:27 AM, Thomas Huth wrote:
> On 15/11/2019 11.20, Janosch Frank wrote:
>> On 11/15/19 11:04 AM, Thomas Huth wrote:
>>> On 24/10/2019 13.40, Janosch Frank wrote:
>>>> If the host initialized the Ultravisor, we can set stfle bit 161
>>>> (protected virtual IPL enhancements facility), which indicates, that
>>>> the IPL subcodes 8, 9 and are valid. These subcodes are used by a
>>>> normal guest to set/retrieve a IPIB of type 5 and transition into
>>>> protected mode.
>>>>
>>>> Once in protected mode, the VM will loose the facility bit, as each
>>>
>>> So should the bit be cleared in the host code again? ... I don't see
>>> this happening in this patch?
>>>
>>>  Thomas
>>
>> No, KVM doesn't report stfle facilities in protected mode and we would
>> need to add it again in normal mode so just clearing it would be
>> pointless. In protected mode 8-10 do not intercept, so there's nothing
>> we need to do.
> 
> Ah, ok, that's what I've missed. Maybe replace "the VM will loose the
> facility bit" with "the ultravisor will conceal the facility bit" ?
> 
>  Thomas
> 


Sure

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