Re: [Qemu-devel] [Qemu-ppc] [PATCH] spapr: Add H-Call H_HOME_NODE_ASSOCIATIVITY

[Laurent Vivier]

On 18/12/2018 11:50, Greg Kurz wrote:
> On Tue, 18 Dec 2018 11:00:01 +0100
> Laurent Vivier <address@hidden> wrote:
> 
>> On 18/12/2018 10:23, Greg Kurz wrote:
>>> On Tue, 18 Dec 2018 08:50:00 +0100
...
>>> Also, even if linux only seems to call this with 0x1, this is a
>>> limitation from a LoPAPR standpoint. Not sure H_PARAMETER is the
>>> appropriate return value if flags is 0x2 since the guest did
>>> nothing wrong... I'd rather return H_FUNCTION in this case.  
>>
>> The doc says:
>>
>>   H_Function:  The function is not supported
>>   H_Parameter: Unsupported flag parameter value
>>
>> in that case function is supported but not the flag, so I think
>> H_PARAMETER is a better choice.
>>
> 
> Well... neither LoPAPR, nor IBM confidential PAPR+ do say anything
> about partial support for this hcall. If the guest was to use the
> flags == 0x2 variant, eg, some closed-source OS supporting PAPR,
> it could be legitimately confused to get an H_PARAMETER error when
> passing supposedly valid parameters... how to cope with that ?
> On the other hand, if QEMU cannot honor the flags == 0x2 variant
> and returns H_FUNCTION then the OS can recover since it is
> required by the specification.

You have certainly access to more information than I have, so I'll
change H_PARAMETER to H_FUNCTION.

Thanks,
Laurent