Re: [Xen-devel] XSAVE save/restore shortcomings

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Jan Beulich wrote on 2013-09-06:
>>>> On 06.09.13 at 09:20, "Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx> wrote:
>> Jan Beulich wrote on 2013-09-06:
>>> So here we are: Paolo quotes the doc stating that the layout is
>>> fixed
>> Layout is not equal to the offset.
> 
> Sorry, I don't follow. What does "The layout of the XSAVE/XRSTOR save
> area is fixed" mean to you then?
My understanding is that "fixed" means "the first area always is FPU/SSE(offset 
0, size 512), the second area always is header(offset 512, size64) and for 
other areas, you must check the CPUID to know the details". Not the offset of 
each feature is fixed. 
See the Table 4-20 in Intel SDM volume 2, it even puts the area3 behind area4.

> 
> Jan


Best regards,
Yang



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