Re: [Xen-devel] [V4] x86/xsaves: calculate the xstate_comp_offsets base on xstate_bv

[Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>]

On Tue, Mar 22, 2016 at 04:53:02AM -0600, Jan Beulich wrote:
> >>> On 16.03.16 at 13:12, <shuai.ruan@xxxxxxxxxxxxxxx> wrote:
> 
> Don't you need to use xcomp_bv here? That's what "Extended
> Region of an XSAVE Area" in SDM Vol 1 suggests to me.
> 
"OPERATION OF XRSTORS" and "OPERATION OF XSAVES" in SDM Vol1.

For xsaves:
"Execution of XSAVES performs the init optimization to reduce the amount
of data written to memory."

For xrstors:
"XRSTORS updates state component i based on the value of bit i in the
XSTATE_BV field of the XSAVE header".

> >      /* Set XSTATE_BV and XCOMP_BV.  */
> >      xsave->xsave_hdr.xstate_bv = xstate_bv;
> >      xsave->xsave_hdr.xcomp_bv = v->arch.xcr0_accum | 
> > XSTATE_COMPACTION_ENABLED;
> > +    setup_xstate_comp(xstate_comp_offsets, xstate_bv);
> 
> Same here then I think.
> 
> Jan
> 
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