From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ross Philipson <ross.philipson@citrix.com>
Subject: Re: [PATCH 5/5] xen: Add V4V implementation - padding
 question
Date: Tue, 11 Jun 2013 13:40:37 -0400
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Cc: Tim Deegan <tim@xen.org>
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On 06/11/2013 01:25 PM, Tim Deegan wrote:
> At 13:10 -0400 on 11 Jun (1370956242), Ross Philipson wrote:
>>>
>>>>> ...
>>>>> +struct v4v_info
>>>>> +{
>>>>> +    uint64_t ring_magic;
>>>>> +    uint64_t data_magic;
>>>>> +    evtchn_port_t evtchn;
>>>>
>>>> Missing padding at the end?
>>>>
>>>
>>> ack.
>>>
>>
>> At one point during the review of an earlier version of the V4V patch
>> set, Jan requested that this pad be added to the v4v_info struct. I
>> understand the padding in all the other structs but I don't understand
>> this one. This struct is not included in any other structs and is not
>> followed by any data.
>
> 64-bit Xen would see this as a 24-byte struct, even without explicit
> padding.  That would surprise a 32-bit guest that allocated what it saw
> as a 20-byte struct for Xen to copy into.

Ah yes, of course. Thanks for the quick response.

Ross

>
> Tim.