[CRIU] [PATCH 06/14] checkpoint: Add dumping of FPU state

[Pavel Emelyanov]

On 12/20/2012 12:36 AM, Cyrill Gorcunov wrote:
> On Thu, Dec 20, 2012 at 12:26:09AM +0400, Pavel Emelyanov wrote:
>> On 12/19/2012 08:31 PM, Cyrill Gorcunov wrote:
>>>
>>> The dumping of FPU state is done with help of ptrace
>>> facility. There are two cases which we need to handle
>>> depending on which features are available on host machine
>>>
>>> 1) The dump via ptrace(PTRACE_GETFPREGS ...)
>>>
>>>    In this case the kernel will use fxsave approach
>>>    inside the kenrel and provides us back the data
>>>    encoded in i387_fxsave_struct format.
>>>
>>> 2) The dump via ptrace(PTRACE_GETREGSET ...)
>>>
>>>    In this case the kernel will use xsave approach
>>>    inside the kernel and provides us back the data
>>>    encoded in xsave_struct format
>>
>> Doesn't kernel decide itself what way to get FPU stuff to use?
> 
> No, it doesn't. For backward compatibility reason. Previously

If it's for backward compatibility, then one cmd should be superior
to the other. Are they such? Or do they report different stuff?

> there were no AVX extension thus old programs which are
> note ready for new registers should not fail when they do
> PTRACE_GETFPREGS/PTRACE_SETFPREGS.
> 
> 	Cyrill
> .
>