Re: [XenPPC] Location to hook setting ppc_md.enable_pmcs for xen

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

On Mar 27, 2007, at 6:57 AM, Christian Ehrhardt wrote:

> How does the inclusion of the code in the subdir platform/xen work  
> in xenppc-linux - Does it replace the bare metal code in platform/ 
> pseries or does it "extend" it in any way?
Please go with option (b).  Until we actually merge with upstream we  
try to keep non-xen code changes to a minimum.  It means duplicating  
some code, but that is ok.

> Xen has has at least a completely own define_machine section there  
> so I assume "replace".
> The issue is that I ask myself if I should add something like:
> a) in function "pSeries_setup_arch" of "arch/powerpc/platforms/ 
> pseries/setup.c"
>     ...
> +   if (?XEN?)
> +       ppc_md.enable_pmcs = pseries_xen_enable_pmcs;
> m   else if (firmware_has_feature(FW_FEATURE_LPAR))
>         ppc_md.enable_pmcs = pseries_lpar_enable_pmcs;
>     else
>         ppc_md.enable_pmcs = power4_enable_pmcs;
>     ...
>
> or
>
> b) go to the xen path and do this in function "xen_setup_arch" of  
> "arch/powerpc/platforms/xen/setup.c"
> with something like this:
>     ...
>         xen_setup_smp();
>     #endif
>
> +        ppc_md.enable_pmcs = pseries_xen_enable_pmcs;
>
>         printk(KERN_INFO "Using Xen idle loop\n");
>     ...
>
> According to the Makefile of "arch/powerpc/plattforms" both are  
> build anyway.
> As far as I read it in the code the platform is detected at boot  
> time and the
> appropriate ppc_md structure gets selected which should be the only  
> xen structure in our case.
> This would argue for variant b) to implement it in "arch/powerpc/ 
> platforms/xen/*"
> Can someone with more experience in that area please send an ack  
> for b) or correct me?
> --
>
> Grüsse / regards, Christian Ehrhardt
>
> IBM Linux Technology Center, Open Virtualization
> +49 7031/16-3385
> Ehrhardt@xxxxxxxxxxxxxxxxxxx
> Ehrhardt@xxxxxxxxxx
>
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