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

[David Gibson]

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.

-- 
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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