Re: [Qemu-devel] [PATCH] memory: make ram device read/write endian sensitive

[Paolo Bonzini]

On 23/02/2017 17:08, Peter Maydell wrote:
> On 23 February 2017 at 15:58, Paolo Bonzini <address@hidden> wrote:
>> However, DEVICE_NATIVE_ENDIAN would have to be paired with tswap, which
>> the current code does not do, hence the bug.  To have no swap at all,
>> you'd need DEVICE_HOST_ENDIAN.
> 
> Yes, I agree that the current ramdevice code has this bug (and
> that we can fix it by any of the various options).

Good. :)

>>> AIUI what we want for this VFIO case is "when the guest does
>>> a 32-bit write of 0x12345678 then the bytes are 0x12 0x34 0x56 0x78
>>> regardless of whether TARGET_BIG_ENDIAN or not".
>>
>> No, I don't think so.  This is not specific to VFIO.  You can do it with
>> any device, albeit VFIO is currently the only one using ramd regions.
> 
> The commit message in the patch that started this thread off
> says specifically that "VFIO PCI device is little endian".
> Is that wrong?

Yes, I think it's a red herring.  Hence my initial confusion, when I
asked "would Yongji's patch just work if it used DEVICE_BIG_ENDIAN and
beNN_to_cpu/cpu_to_beNN".

Paolo