Re: [XenPPC] fast_resume instead of full_resume after hdec_out

[Hollis Blanchard <hollisb@xxxxxxxxxx>]

Sounds reasonable to me.

When I get a chance I'll try it out; I need to do a little work to track
upstream Xen changes anyways. I don't think I'll have time in the next
two weeks though (just FYI)...

On Tue, 2007-09-11 at 04:22 +0000, HYEONSEUNG JANG wrote:
> In handling hdec exception, non-volatile registers are saved because
> context_switch() may be called in the do_softirq(). The fact that we
> reach to 'hdec_out' means that there has been no context_switch()
> called. But currently 'fast_resume' is called after 'hdec_out'
> 
> I think there seems to be no reason to restore non-volatiles at this
> point. Becasue MSR_EE is alwyas 0, 'fast_resume' will be enough like the
> following. It seems to work well in our HW. Please give me comments or
> something.
> 
> - Hyeonseung Jang.
> 
> 
> 
> diff -r 9071521d4864 xen/arch/powerpc/powerpc64/exceptions.S
> --- a/xen/arch/powerpc/powerpc64/exceptions.S Fri Sep 07 11:39:10 2007 +0100
> +++ b/xen/arch/powerpc/powerpc64/exceptions.S Tue Sep 11 11:38:25 2007 +0900
> @@ -514,6 +514,7 @@ hdec_out:
>  hdec_out:
>      addi r1, r1, STACK_FRAME_OVERHEAD   /* restore stack to cpu_user_regs */
>      LOAD_GPRS r14, r15, r1              /* we clobbered r14/r15 in the loop 
> */
> +    b fast_resume
>  
>  /* r1 points to the to-be-restored cpu_user_regs. These could be 
> mid-hypervisor
>   * stack (returning into elsewhere in Xen) or at the top of the stack
> 
> 
> 
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-- 
Hollis Blanchard
IBM Linux Technology Center


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