Re: [Qemu-ppc] [Qemu-devel] [PATCH v3 4/4] target-ppc: Handle ibm, nmi-register RTAS call

[Aravinda Prasad]

On Tuesday 11 November 2014 11:41 AM, David Gibson wrote:
> On Tue, Nov 11, 2014 at 11:18:05AM +0530, Aravinda Prasad wrote:
>>
>>
>> On Tuesday 11 November 2014 08:49 AM, David Gibson wrote:
>>> On Thu, Nov 06, 2014 at 03:30:01PM +0530, Aravinda Prasad wrote:
>>>> On Wednesday 05 November 2014 09:16 PM, Tom Musta wrote:
>>>>> On 11/5/2014 2:32 AM, Alexander Graf wrote:
>>>>>> On 05.11.14 08:13, Aravinda Prasad wrote:
>>>
>>> [snip]
>>>>>>> +       /*
>>>>>>> +        * ori r3,r3,KVMPPC_H_REPORT_MC_ERR. The KVMPPC_H_REPORT_MC_ERR
>>>>>>> +        * value is patched below
>>>>>>> +        */
>>>>>>> +1:     ori     3,3,0
>>>>>
>>>>> Why do "li 3,0" followed by "ori 3,3,X"?  Isn't this just "li 3,X" ?  
>>>>> (aka "addi 3,0,X")
>>>>
>>>> I remember I first tried doing li r3,X but faced some problem (but not
>>>> able to exactly recall what was the problem) may be due to not familiar
>>>> with ppc assembly.
>>>
>>> This would be because with the offset to the private hcalls, the
>>> actual hcall number is 0xf003, which means an li instruction will sign
>>> extend it incorrectly. So you will need two instructions to load the
>>> number.
>>
>> hmm.. ok
> 
> At least, I think you'll need to instructions.  I don't remember for
> certain if 'ori 3,0,X' will OR X with literal 0 or the contents of r0.

It is ORed with r0

>From ISA:

ori RA,RS,UI

(RA) <- (RS) | (0 || UI)

The contents of register RS are ORed with 0 || UI and
the result is placed into register RA.

> 

-- 
Regards,
Aravinda