Re: [Qemu-devel] [PATCH 1/2] virtio-pci: Fix endianness of virtio config

[Alexander Graf]

On 11.01.2012, at 01:07, Anthony Liguori wrote:

> On 01/10/2012 06:07 PM, Alexander Graf wrote:
>> From: Benjamin Herrenschmidt<address@hidden>
>> 
>> The virtio config area in PIO space is a bit special. The initial
>> header is little endian but the rest (device specific) is guest
>> native endian.
>> 
>> The PIO accessors for PCI on machines that don't have native IO ports
>> assume that all PIO is little endian, which works fine for everything
>> except the above.
>> 
>> A complicated way to fix it would be to split the BAR into two memory
>> regions with different endianess settings, but this isn't practical
>> to do, besides, the PIO code doesn't honor region endianness anyway
>> (I have a patch for that too but it isn't necessary at this stage).
>> 
>> So I decided to go for the quick fix instead which consists of
>> reverting the swap in virtio-pci in selected places, hoping that when
>> we eventually do a "v2" of the virtio protocols, we sort that out once
>> and for all using a fixed endian setting for everything.
>> 
>> Unfortunately, that mean moving virtio-pci from Makefile.objs to
>> Makefile.target so we can use TARGET_WORDS_BIGENDIAN which would
>> otherwise be poisoned.
>> 
>> Signed-off-by: Benjamin Herrenschmidt<address@hidden>
>> Signed-off-by: Alexander Graf<address@hidden>
>> [agraf: keep virtio in libhw and determine endianness through a
>>         helper function in exec.c]
> 
> Both:
> 
> Reviewed-by: Anthony Liguori <address@hidden>

Cool :). Queued up in ppc-next.


Alex