Re: [Qemu-devel] [PATCH] virtio-pci: replace byte swap hack

[Alexander Graf]

Am 06.01.2013 um 19:26 schrieb Blue Swirl <address@hidden>:

> On Sun, Jan 6, 2013 at 1:17 PM, Alexander Graf <address@hidden> wrote:
>> 
>> On 30.12.2012, at 13:55, Blue Swirl wrote:
>> 
>>> Remove byte swaps by declaring the config space
>>> as native endian.
>> 
>> This is wrong. Virtio-pci config space is split into 2 regions. One with 
>> native endianness, the other one with little endian.
> 
> True. I must say that this is poor architectural design in multiple
> ways. The endianness problem is aggravated by device being also
> instantiated by other devices, so we can't (at least easily) pass an
> endianness flag from above, or make two devices that are selected by
> the board. Another problem is that the offset changes dynamically
> depending on if MSIX is enabled or not. The design is probably also
> fixed by the guest driver assumptions and can't ever be improved.
> Paravirtual devices should have cleaner design than what for example
> original PC devices have, not more insane. :-(

I guess now you understand my wording in the comment that your patch removes a 
bit better :).


Alex