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Date: Wed, 23 Mar 2011 09:33:09 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: [Qemu-devel] Re: [PATCH 07/11] eeprom93xx: Use the new hack macro
 to avoid duplicate field names
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To: quintela@redhat.com
Cc: Jan Kiszka <jan.kiszka@siemens.com>, Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org

On 03/23/2011 09:14 AM, Juan Quintela wrote:
> Anthony Liguori<anthony@codemonkey.ws>  wrote:
>> On 03/23/2011 04:58 AM, Juan Quintela wrote:
>>> Anthony Liguori<aliguori@us.ibm.com>   wrote:
>>>> I don't fully understand this hack business but we need field to be unique so..
>>>>
>>>> Signed-off-by: Anthony Liguori<aliguori@us.ibm.com>
>>>> ---
>>>>    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.