Re: [Xen-devel] [v7][PATCH 13/16] libxl: construct e820 map with RDM information for HVM guest

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

> This approach looks like it should work, and I think given the point in
> the release it would be acceptable for 4.6.
>
> However long term I think it might make sense to try and reuse one of
> the existing libxl__arch hooks, i.e.
> libxl__arch_domain_init_hw_description or
> libxl__arch_domain_finalise_hw_description. On ARM these are to do with
> setting the Device Tree Blob, which included the memory map, so it is
> somewhat morally equivalent to configuring the e820 on x86, I think.
>
> Those hooks are only called from libxl__build_pv today, but calling them
> from libxl__build_hvm seems like it would be good too.
But seems this is raising some potential risks, isn't this? Although 
libxl__arch_domain_init_hw_description() and 
libxl__arch_domain_finalise_hw_description() are NOP to x86, they're 
really working on ARM side. So if we call them inside 
libxl__build_hvm(), any affects to ARM? I'm not very sure at this point 
unless anyone can validate this change on ARM, or you really ensure my 
concerns is unnecessary.
> In particular I think a call to
> libxl__arch_domain_finalise_hw_description could be inserted just before
> xc_hvm_build, which is similar to PV where it precedes
> xc_dom_build_image, and is where you would want to setup the e820.
>
> libxl__arch_domain_init_hw_description I think would still be a NOP on
> x86, but it should probably go either just after the call to
> libxl__domain_firmware.
>
> Tiejun, would you be willing to commit to refactoring this and the
> issues which Ian raised in response to #11 and #16 a subsequent clean up
> series? I don't think it would even need to wait for the freeze to be
> over to be posted (although it may need to wait to be applied).
Yes, I'd like to follow this once my concerns above can be eliminated.

Thanks
Tiejun

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