> Here is the concrete example:
> * guest writes to MMIO
> * KVM passes MMIO information (physical address, number of
> bytes, value) to qemu
The value is saved in memory, is it bigendian or
littleendian?
> * Qemu knows from the address that this access is for a
> passthough device, a special case the administrator has
> pre-configured * Qemu does mmap(/dev/mem), and writes "length"
When qemu writes value, Can qemu know what
mode(bigendian/littleendian it is running)?
Qemu can run on bigendian in IA64.
> bytes of "value" at offset "address".
>
Hollis Blanchard wrote:
> On Sun, 2008-01-13 at 11:42 +0200, Avi Kivity wrote:
>
>> Do we really need to propagate endianness all the way to the user?
>> Perhaps libkvm could call the regular mmio functions and do the
>> transformation itself.
>>
>> Or maybe even the kernel can do this by itself?
>
> The kernel *already* does this by itself, and I'm attempting to
> explain why that is not sufficient.
>
> My point is precisely that the endianness information must be
> propagated to the user, otherwise the user may not have all the
> information it needs to emulate it.
>
> Here is the concrete example:
> * guest writes to MMIO
> * KVM passes MMIO information (physical address, number of
> bytes, value) to qemu
> * Qemu knows from the address that this access is for a
> passthough device, a special case the administrator has
> pre-configured * Qemu does mmap(/dev/mem), and writes "length"
> bytes of "value" at offset "address".
>
> Now here's the catch: what endianness does qemu use when doing the
> write? If qemu only does BE, then a LE access from the guest will be
> byte-reversed when presented to the real hardware.
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