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

[Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>]

On Wed, Mar 23, 2016 at 09:28:03AM +0800, Shuai Ruan wrote:
> 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".
> 
Ignore this. You are right.
I misunderstand some XSAVES/XRSTORS behaviors in SDM . In the previous versions,
I use xcom_bv to caculate comp_offset (but changing to xstate_bv in this
version:( ).
Thanks.
> > >      /* 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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> > http://lists.xen.org/xen-devel
> 
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