Re: [Xen-devel] [PATCH v3 15/16 - RFC] x86: make Xen early boot code relocatable

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.04.16 at 14:33, <daniel.kiper@xxxxxxxxxx> wrote:
> Every multiboot protocol (regardless of version) compatible image must
> specify its load address (in ELF or multiboot header). Multiboot protocol
> compatible loader have to load image at specified address. However, there
> is no guarantee that the requested memory region (in case of Xen it starts
> at 1 MiB and ends at 17 MiB) where image should be loaded initially is a RAM
> and it is free (legacy BIOS platforms are merciful for Xen but I found at
> least one EFI platform on which Xen load address conflicts with EFI boot
> services; it is Dell PowerEdge R820 with latest firmware). To cope with
> that problem we must make Xen early boot code relocatable. This patch does
> that.

I don't follow: If we have to specify a load address, and if the
loader is required to put us there or fail, how does the code being
made relocatable help? And how does moving ourselves from 1Mb
to 2Mb make it any less likely that the designated address range is
actually free? Perhaps it's just the description that's misleading
here...

Even with that resolved I expect - as a result of the discussion on
the hackathon - quite a bit of change to this patch, so I don't view
actually reviewing the code as usefully spent time.

Jan


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