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Re: [Xen-devel] [PATCH V2 00/12] arm64 EFI stub

On Mon, 2014-07-21 at 17:43 -0700, Roy Franz wrote:
> I think this patchset is in good shape, with the exception of the usage of
> the EFI memory map, which I am looking for some suggestions on.  The current
> implementation populates the bootinfo memory bank list from the EFI memory 
> map,
> rather than from the device tree, and doesn't use any reserved ranges.  This
> works, however the EFI memory map can contain a lot of entries, many of which
> are small.  Depending on the layout, this could trigger the code that sets
> up the frametable to discard most of memory.  Also, as a side effect of some
> memory being ignored to manage the frametable size, the EFI stub needs to
> ensure that it loads modules into memory that XEN is going to map. The
> FVP model has 2GBytes of DRAM at 0x80000000 and another 2 at 0x800000000,
> so the disjoint case is common.
> It seems that both these problems go largely away if sparse frametable 
> mappings are
> supported, but I'm not sure how much effort that would be.  I think most
> of the work done to handle things robustly with the non-sparse frametable
> would not apply once a sparse frametable is supported.  Does adding support
> for a sparse frametable mapping seem like a reasonable way forward on this?

I think so, we need this for many reasons other than the issues it
causes with EFI anyway.


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