Re: [XenPPC] [xenppc-unstable] [ppc] Turn on Save and Restore of VMX registers

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

On Jun 13, 2006, at 7:09 PM, Segher Boessenkool wrote:

> >  /* So you might think that we could use the VRSAVE register to
> >   * streamline this but "If this [VRSAVE] approach is taken it  
> > must be
> >   * applied rigorously".
> I have no idea what this comment is supposed to mean.  If you use
> VRSAVE to select which regs to save and which not, it often hurts
> to do that selection per register; but doing it per block of four
> stil pays off.  (About equal to blocks of eight in my profiling,
> btw.  Do you own profiling!)
Ok, its a bad comment :).
The point is that, the hypervisor cannot depend on the OSes above us  
to use VRSAVE at all, so we have to S&R the whole shebang.
I'll write a clearer comment.

> >         /* r0 as the second operand is considered 0 */
> NOT AT ALL.  Binary pattern 0b00000 for RA means literal 0 instead
> of GPR0, sure.  And the assembler you use just uses CCCP to
> translate "r0" into a literal 0.  But some other assemblers
> do not.  So please just write "0" when you mean "0".
point taken
thanks
-JX

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