Re: [Qemu-ppc] KVM and variable-endianness guest CPUs

Peter Maydell
2014-01-27T23:49:55Z

On 27 January 2014 23:34, Benjamin Herrenschmidt
<benh@kernel.crashing.org> wrote:
> On Wed, 2014-01-22 at 20:02 +0000, Peter Maydell wrote:
>>
>> Defining it as being always guest-order would mean that
>> userspace had to continually look at the guest CPU
>> endianness bit, which is annoying and awkward.
>>
>> Defining it as always host-endian order is the most
>> reasonable option available. It also happens to work
>> for the current QEMU code, which is nice.
>
> No.
>
> Having a byte array coming in that represents what the CPU does in its
> current byte order means you do *NOT* need to query the endianness of
> the guest CPU from userspace.

Er, what? If we make the array be guest's current order
then by definition userspace has to look at the guest's
current endianness. I agree that would be bad. Either
of the two current proposals (host kernel order; guest
CPU's native/natural/default-byte-order) avoid it, though.

-- PMM