[patch][5/5] powerpc: Add the general support for EmbeddedFloating-Point instructions

[Zhu Ebony-r57400]

> -----Original Message-----
> From: Benjamin Herrenschmidt [mailto:benh at kernel.crashing.org] 
> Sent: 2007年1月12日 19:06
> To: Zhu Ebony-r57400
> Cc: Kumar Gala; linuxppc-dev at ozlabs.org; paulus at samba.org
> Subject: RE: [patch][5/5] powerpc: Add the general support 
> for EmbeddedFloating-Point instructions
> 
> 
> > > Why do we need a separate ret_from_except_spe_full?
> > 
> > I'm not sure if the kernel will return from exception in a 
> > multi-thread way, but the truth is if restoring EVRs in exsiting 
> > ret_from_except_full, some non-SPE exception will try to 
> retore EVR. 
> > At that time, the MSR[SPE] may not be enabled, which will 
> cause error.
> 
> Hrm... you can restore them before returning from the 
> exception if you are careful about doing that with 
> preempt/irqs off I suppose.
> 
> Ben.

If so, the existing ret_from_except_full needs to be modified
since it only restores 32bit GPRs, and I'm afraid the instructions to operate
32bit GPRs will break the hi-words of 64bit GPRs.

Ebony