Re: [Qemu-devel] [PATCH v2] target-ppc: gdbstub allow byte swapping for reading/writing registers

[Peter Maydell]

On 16 January 2014 17:51, Alexander Graf <address@hidden> wrote:
>> Am 16.01.2014 um 18:41 schrieb Peter Maydell <address@hidden>:
>> Also see my remarks on the previous patch series suggesting
>> that we should look at this in a more holistic way than
>> just randomly fixing small bits of things. A good place
>> to start would be "what should the semantics of stl_p()
>> be for a QEMU where the CPU is currently operating with
>> a reversed endianness to the TARGET_WORDS_BIGENDIAN
>> setting?".
>
> That'd open a giant can of worms that I'd rather not open.

If you don't want to open the can of worms then your
correct path is to use QEMU's existing mechanisms for
BE/LE support -- build a separate executable for the
other endianness, which will then have TARGET_WORDS_BIGENDIAN
set appropriately, and the gdb register read functions
will work correctly.

Attempting to handle either-endian guests in the same
executable is exactly opening the can of worms, and if
we're doing it we should do it with some kind of plan
of attack for killing the worms.

> RTAS for example is still BE regardless of guest endianness.

"Always BE" accesses are easy -- they should be done
with the versions of the ld/st functions which have
_be_ in them. If there are places using the plain
stl_p() functions and assuming they're bigendian, they
should be fixed.

thanks
-- PMM