Re: [PATCH v2 02/10] ppc: Remove stub of PPC970 HID4 implementation

[Thomas Huth]

On 07/01/2020 19.05, BALATON Zoltan wrote:
> On Tue, 7 Jan 2020, Greg Kurz wrote:
>> On Tue, 7 Jan 2020 18:32:15 +0100
>> Greg Kurz <address@hidden> wrote:
>>
>>> On Tue,  7 Jan 2020 15:48:19 +1100
>>> David Gibson <address@hidden> wrote:
>>>
>>>> The PowerPC 970 CPU was a cut-down POWER4, which had hypervisor
>>>> capability.
>>>> However, it can be (and often was) strapped into "Apple mode", where
>>>> the
>>>> hypervisor capabilities were disabled (essentially putting it always in
>>>> hypervisor mode).
>>
>> Isn't it supervisor mode instead of hypervisor mode ?
> 
> By the way, do you know if this strapping is hardware or software based?
> So is it the firmware that disables it on Apple hardware or is it some
> CPU pin connected somewhere on the motherboard or it's within the CPU
> and cannot be changed? I wonder if it's theoretically possible to
> re-enable it on an Apple G5 or we would likely never see a PowerPC 970
> with HV enabled?

I don't know how Apple disabled it, but you can buy a used Terrasoft YDL
PowerStation if you want to see it in action.

 Thomas