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

[Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx>]

> 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.
Ah, much clearer already.

Do we really have to?  Can't we, for example, define the supervisor
vs. hypervisor ABI wrt. VMX to be "if the hypervisor wants to use
any VMX regs, it better S&R those itself"?  And when switching
supervisor context, just swap-em all out.  Although perhaps this is
just what the full code is doing, souldn't tell from the patch alone :-)

> I'll write a clearer comment.
Much appreciated.

> > >         /* 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
No, _thank you_.  Let's exterminate this disease before it spreads
even further :-)


Segher


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