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From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 23 Feb 2017 10:02:48 +0000
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Subject: Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, Yongji Xie <xyjxie@linux.vnet.ibm.com>, QEMU Developers <qemu-devel@nongnu.org>, Alex Williamson <alex.williamson@redhat.com>, zhong@linux.vnet.ibm.com, David Gibson <david@gibson.dropbear.id.au>, Paul Mackerras <paulus@samba.org>

On 23 February 2017 at 08:35, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
>
> On 23/02/2017 05:20, Alexey Kardashevskiy wrote:
>> First, Paolo is right and ram_device_mem_ops::endianness should be
>> host-endian which happens to be little in our test case (ppc64le)
>
> So you tested a ppc64 BE guest and it works?
>
>> Keep things where they are in the VFIO department and just fix
>> ram_device_mem_ops::endianness?
>
> I would fix the ram_device_mem_ops.  Either by introducing
> DEVICE_HOST_ENDIAN(*) or with Yongji's patch.
>
> (*) DEVICE_NATIVE_ENDIAN is special cased all over the place
>     because the same device (in a file that's compiled just once)
>     can be either little- or big-endian.  DEVICE_HOST_ENDIAN can
>     be a simple #define to either DEVICE_LITTLE_ENDIAN or
>     DEVICE_BIG_ENDIAN, because host endianness is the same for
>     all QEMU binaries.  It's literally half a dozen lines of code.

I'm really not convinced we need DEVICE_HOST_ENDIAN. RAM
areas should be target-endian (you can probably define
"target endianness" as "the endianness that RAM areas have".)

-- PMM