Subject: Re: [PATCH] powerpc: OE=1 Form Instructions Not Decoded Correctly

From: Paul Mackerras <[email-masked]>
Date: Mon, 9 Sep 2013 08:35:59 +1000

On Fri, Sep 06, 2013 at 10:13:00AM -0500, Tom Musta wrote:
> To: [email-masked]
> Subject: [PATCH] powerpc: OE=1 Form Instructions Not Decoded Correctly
> From: Tom Musta <[email-masked]>
> 
> PowerISA uses instruction bit 21 to indicate that the overflow (OV) bit
> of the XER is to be set, as well as its corresponding sticky bit (SO).
> This patch addresses two defects in the implementation of the PowerISA
> single step code for this category of instructions:  (a) the OE=1 case
> is not correctly accounted for in the case statement for the extended
> opcode handling.  (b) the implementation is not setting XER[OV] and
> XER[SO].

Are you seeing any actual problems arising from the OE=1 instructions
not being emulated?  This code was designed primarily for emulating
instructions in the kernel, which is written in C, and the C compiler
doesn't emit OE=1 instructions -- or at least it didn't in the past.
So, does the impetus for this change come because the C compiler is
now emitting these instructions, or because this code is being used on
non-kernel instructions, or just for completeness?  Your patch
description needs to include answers to these kinds of questions.

Also, you need to indent your code correctly according to
Documentation/CodingStyle.

Paul.