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

[Paolo Bonzini <pbonzini@redhat.com>]

On 23/02/2017 15:35, Peter Maydell wrote:
> On 23 February 2017 at 12:53, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>
>>
>> On 23/02/2017 13:26, Peter Maydell wrote:
>>> On 23 February 2017 at 11:43, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>>> On 23/02/2017 12:34, Peter Maydell wrote:
>>>>> We should probably update the doc comment to note that the
>>>>> pointer is to host-endianness memory (and that this is not
>>>>> like normal RAM which is target-endian)...
>>>>
>>>> I wouldn't call it host-endianness memory, and I disagree that normal
>>>> RAM is target-endian---in both cases it's just a bunch of bytes.
>>>>
>>>> However, the access done by the MemoryRegionOps callbacks needs to match
>>>> the endianness declared by the MemoryRegionOps themselves.
>>>
>>> Well, if the guest stores a bunch of integers to the memory, which
>>> way round do you see them when you look at the bunch of bytes?
>>
>> You see them in whatever endianness the guest used.
> 
> I'm confused. I said "normal RAM and this ramdevice memory are
> different", and you seem to be saying they're the same. I don't
> think they are (in particular I think with a BE guest on an
> LE host they'll look different).

No, they look entirely the same.  The only difference is that they go
through MemoryRegionOps instead of memcpy.

Paolo