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Re: [Qemu-ppc] [PATCH 16/16] target-ppc: Convert to new ldst opcodes

From: Benjamin Herrenschmidt
Subject: Re: [Qemu-ppc] [PATCH 16/16] target-ppc: Convert to new ldst opcodes
Date: Thu, 05 Sep 2013 21:40:55 +1000

On Thu, 2013-09-05 at 11:08 +0200, Alexander Graf wrote:
> On 04.09.2013, at 23:05, Richard Henderson wrote:
> > This lets us change "le_mode" to "end_mode" and fold away nearly all
> > of the tests for the current cpu endianness, and removing all of the
> > explicitly generated bswap opcodes.

Only nit: I find "end_mode" a very confusing identifier :-) "end"
usually means something else ! Why not endian_mode ?
> > 
> > Cc: address@hidden
> > Signed-off-by: Richard Henderson <address@hidden>
> No complaints from me, apart from the usual "LE mode isn't necessarily what 
> you think it is on PPC" one. But the code would be as broken as before IIUC.
> Ben, you had some insight in how LE mode on different PPC flavors work. Could 
> you please make sure we're not walking into the wrong direction here?

I haven't seen the patch itself for some reason (and I'm about to go off
for a few days). The early day powerpc endian mode can be safely ignored
I think, I don't even remember the details myself, I think it induced
some changes to the byte lanes ordering on the bus and thus required the
host bridge to be adjusted.

The embedded PPCs have simply a per-page E bit in the TLB controlling
the endianness of accesses through the translation, the endianness is
"clean" in that case, and the bus doesn't flip around so it's akin to
what P7 does but with a finer granularity.


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