[CRIU] [PATCH 08/14] restore: Reserve space in restorer for FPU frame

[Pavel Emelyanov]

On 12/20/2012 12:40 AM, Cyrill Gorcunov wrote:
> On Thu, Dec 20, 2012 at 12:26:31AM +0400, Pavel Emelyanov wrote:
>> On 12/19/2012 08:31 PM, Cyrill Gorcunov wrote:
>>>
>>> For code simplicity we reserve the maximum size which
>>> might be needed to form an FPU frame (ie for both
>>> xsave and fxsave operations).
>>>
>>> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
>>> ---
>>>  include/restorer.h | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>>
>>
>>
>>> +
>>> +	bool				has_fpu;
>>> +	union {
>>> +		struct xsave_struct	xsave;
>>> +		unsigned char		__pad[sizeof(struct xsave_struct) + FP_XSTATE_MAGIC2_SIZE];
>>
>> What is this padding for?
> 
> We need 4 bytes to be allocated right after xsave,

Why?

> and technically it's better
> to refer to it as singe block in structure, ie union.

Why is struct + unsigned worse?

> 	Cyrill
> .
>