Re: [PATCH 1/1] kvm-s390: Provide guest TOD Clock Get/Set Controls

[Paolo Bonzini <pbonzini@redhat.com>]

On 06/11/2014 09:43, Christian Borntraeger wrote:
> Am 05.11.2014 20:45, schrieb Paolo Bonzini:
>>
>>
>> On 05/11/2014 18:56, Christian Borntraeger wrote:
>>>>>
>>>>> Whether you want to follow that approach or do it as VM attribute
>>>>> straight away, I don't mind much :).
>>> given that top programmable field and epoch are available as ONEREG, lets do the same for TOD.
>>
>> Is the epoch per-cpu?
> 
> two answers :-)
> 
> - the implementation is one epoch per control block, so someone could do that per CPU...but:
> - guest TOD == host TOD + epochdiff. architecture mandates that there is only one TOD per system, so all guest TODs must be synced and so must be all epochdiffs

Got it.  Using VM attrs or ONEREG is the same, you choose.

> As a recap we have now:
> #define KVM_REG_S390_TODPR     (KVM_REG_S390 | KVM_REG_SIZE_U32 | 0x1)
> #define KVM_REG_S390_EPOCHDIFF (KVM_REG_S390 | KVM_REG_SIZE_U64 | 0x2)
> 
> and we would
> add
> #define KVM_REG_S390_TOD       (KVM_REG_S390 | KVM_REG_SIZE_U64 | 0x3) 
> #define KVM_REG_S390_TOD_INDEX (KVM_REG_S390 | KVM_REG_SIZE_U8 | 0x4)

TOD_HIGH?  TOD_EXTRA?  TOD_EXTRA_HIGH?

Paolo