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

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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





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