Re: [Qemu-devel] [Qemu-ppc] [PATCH v3 11/14] ioport: Switch dispatching to memory core layer

[Anthony Liguori]

Peter Maydell <address@hidden> writes:

> On 12 July 2013 23:50, Benjamin Herrenschmidt <address@hidden> wrote:
>> Our experience is that it actually works fine for almost everything
>> except virtio :-) ie mostly TARGET_WORDS_BIGENDIAN is irrelevant (and
>> should be).
>
> I agree that TARGET_WORDS_BIGENDIAN *should* go away, but
> it exists currently. Do you actually implement a CPU which
> does dynamic endianness flipping?

TCG already supports bi-endianness for PPC.  Grep for 'le_mode' in
target-ppc/translate.c to see how the TCG instruction stream is affected
by it.

On PPC, le_mode only really affects load/stores and instruction
decoding.  Any shared data structures between the CPU and OS remain big
endian.

So TARGET_WORDS_BIGENDIAN is still accurate even when le_mode=1.  It's
not the semantic equivalent of changing TARGET_WORDS.

Regards,

Anthony Liguori

> Is it at all efficient
> in the config which is the opposite of whatever
> TARGET_WORDS_BIGENDIAN says?
>
> thanks
> -- PMM