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Re: [Xen-devel] [PROPOSAL] ARM/FDT: passing multiple binaries to a kernel

On 09/05/2013 03:23 PM, Rob Herring wrote:
On Wed, Sep 4, 2013 at 3:43 AM, Andre Przywara
<andre.przywara@xxxxxxxxxx> wrote:
On 09/04/2013 12:00 AM, Rob Herring wrote:

On Tue, Sep 3, 2013 at 10:53 AM, Andre Przywara

But surely there would be some advantage of reuse by using the
multi-boot protocol since Xen, grub, and OS tools already support it
for x86.

Yes, but that is x86 only and multiboot is it's nature quite architecture
specific. The current(?) multiboot v2 spec has no official ARM support (only
x86 and MIPS), so this would need to be "invented" first. While this is
technically easy, ARM software currently has no support for multiboot at
all: not in u-boot and not in Xen.
Multiboot support in Xen lives entirely in the x86 directory, and big parts
of it are even in assembly.

If so, I cannot find the assembly and most of it seems to be moved out
of x86 code now.

There is some code that relocates and maps the multiboot structure: in files in the xen/arch/x86/boot directory, including head.S, reloc.c and setup.c. That would need to be completely rewritten, not only because it deals with multiboot v1, but also because it is scattered throughout the x86 setup code and the initial page setup is different from ARM.

All these things are also done on ARM - but for the device tree already.
Of course proper multiboot v2 support is doable - but please compare the effort needed for this against this one:


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