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

[David Gibson]

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.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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