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

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

On 2015/7/13 18:15, Ian Campbell wrote:
> On Mon, 2015-07-13 at 17:47 +0800, Chen, Tiejun wrote:
> > > 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.
> All ARM guests use the PV code path so there is no risk.
Okay but please take a close look at this,

libxl__build_pv(gc, domid, info, state)
    |
    + libxl__arch_domain_finalise_hw_description(libxl__gc *gc,
                                      libxl_domain_build_info *info,
                                      struct xc_dom_image *dom)

But in our case we need this parameter, struct xc_hvm_build_args *args, 
so how can we handle this conflict? Its not easy to add this, and it 
doesn't make sense as well in pv case.
Thanks
Tiejun  

> If there was some change to ARM to introduce an HVM style guest then it
> would want those hooks called in this place too (and they would need
> fixing as part of implementing such a thing).
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel