[Qemu-devel] Re: [PATCH 07/11] eeprom93xx: Use the new hack macro to avoid duplicate field names

[Anthony Liguori]

On 03/23/2011 09:14 AM, Juan Quintela wrote:
> Anthony Liguori<address@hidden>  wrote:
> > On 03/23/2011 04:58 AM, Juan Quintela wrote:
> > > Anthony Liguori<address@hidden>   wrote:
> > > > I don't fully understand this hack business but we need field to be unique so..
> > > >
> > > > Signed-off-by: Anthony Liguori<address@hidden>
> > > > ---
> > > >    hw/eeprom93xx.c |    2 +-
> > > >    1 files changed, 1 insertions(+), 1 deletions(-)
> > > >
> > > > diff --git a/hw/eeprom93xx.c b/hw/eeprom93xx.c
> > > > index cfa695d..f1d75ec 100644
> > > > --- a/hw/eeprom93xx.c
> > > > +++ b/hw/eeprom93xx.c
> > > > @@ -114,7 +114,7 @@ static const VMStateInfo vmstate_hack_uint16_from_uint8 = {
> > > >    };
> > > >
> > > >    #define VMSTATE_UINT16_HACK_TEST(_f, _s, _t)                           \
> > > > -    VMSTATE_SINGLE_TEST(_f, _s, _t, 0, vmstate_hack_uint16_from_uint8, 
> > > > uint16_t)
> > > > +    VMSTATE_SINGLE_TEST_HACK(_f, _s, _t, 0, vmstate_hack_uint16_from_uint8, 
> > > > uint16_t)
> > > >
> > > >    static bool is_old_eeprom_version(void *opaque, int version_id)
> > > >    {
> > Could we get away with just doing:
> >
> > VMSTATE_UNUSED(3),
> > VMSTATE_UINT8(bar, ...),
> Remember that we are "supposed to be" big/little endian safe.

We always send in network byte order (big endian) so this is safe.

> > That's fully compatible on the wire and seems to be a clearer
> > expression of exactly what the problem is.
> if we are going to break big endian machines, I fully agree.

The migration protocol is always big endian, see:

void qemu_put_be32(QEMUFile *f, unsigned int v)
{
    qemu_put_byte(f, v >> 24);
    qemu_put_byte(f, v >> 16);
    qemu_put_byte(f, v >> 8);
    qemu_put_byte(f, v);
}

So this is completely safe.

Regards,

ANthony Liguori

> Later, Juan.