On 10.04.2011, at 22:06, Aurelien Jarno wrote: > On Sun, Apr 10, 2011 at 09:26:26PM +0200, Alexander Graf wrote: >> >> On 10.04.2011, at 21:25, Aurelien Jarno wrote: >> >>> On Mon, Apr 04, 2011 at 04:32:10PM +0200, Alexander Graf wrote: >>>> The feature bitmap in the s390 virtio machine is little endian. To >>>> address for that, we need to bswap the values after reading them out. >>>> >>>> Signed-off-by: Alexander Graf <ag...@suse.de> >>>> --- >>>> hw/s390-virtio-bus.c | 4 ++-- >>>> 1 files changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/hw/s390-virtio-bus.c b/hw/s390-virtio-bus.c >>>> index 58af164..60e0135 100644 >>>> --- a/hw/s390-virtio-bus.c >>>> +++ b/hw/s390-virtio-bus.c >>>> @@ -223,7 +223,7 @@ void s390_virtio_device_sync(VirtIOS390Device *dev) >>>> cur_offs += num_vq * VIRTIO_VQCONFIG_LEN; >>>> >>>> /* Sync feature bitmap */ >>>> - stl_phys(cur_offs, dev->host_features); >>>> + stl_phys(cur_offs, bswap32(dev->host_features)); >>> >>> Is bswap32 correct here for both big and little endian guests? I don't >>> really understand the reason why a bswap is needed here, especially >>> given that AFAIK this code was already used when using KVM. >> >> This is target specific code. The s390-virtio-bus is s390 specific. And yes, >> the code was also broken with KVM. That's how I first found it actually. >> > > So in short, s390-virtio-bus is specific to big endian machines, but is > using little endian? That looks a bit weired. I guess it's probably to > late to change the specification anyway...
Yeah. In fact, it mixes big and little endian pieces. But it really is too late to change the (unwritten) spec, unfortunately. Alex
