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

[Grant Likely <grant.likely@xxxxxxxxxxxx>]

On Wed, Sep 4, 2013 at 5:41 PM, Rob Herring <robherring2@xxxxxxxxx> wrote:
>> For u-boot Andre has proposed some syntactic sugar over the "fdt"
>> command to make boot.scr more trivial to use. We would of course need to
>> implement support for using it in the relevant distro tools (but they
>> tend to be very distro/machine specific already, e.g. Debian's
>> flash-kernel)
>
> And being machine specific is a PITA. flash-kernel is certainly not
> something we want to expand on. There is not much love for boot.scr
> either. There is work to address what are not really machine
> differences, but largely vendor u-boot differences:
>
> http://www.mail-archive.com/u-boot@xxxxxxxxxxxxx/msg119025.html
>
> One option for u-boot which already supports syslinux style menu files
> is to adopt the syslinux multiboot parsing support:
>
> http://www.syslinux.org/wiki/index.php/Doc/mboot

Even building it into U-Boot is problematic because it leaves older
machines out in the cold. Leif's port of Grub to U-Boot is far more
interesting since the distro can now be in control of the code that
loads the images and jumps into the kernel/hypervisor.

> We need to back-up and consider what this looks like in the end for
> all the pieces and get input from folks on grub, UEFI, and armv8. The
> UEFI answer may be this is a grub problem. For armv8, this proposal
> does match up well as the kernel boot interface for v8 is DT. Despite
> some claims, ACPI will not completely replace DT because of this.

Yes, for UEFI it is absolutely an OS loader problem. UEFI provides an
API and runtime environment. Grub is in general moving towards a boot
menu system and a tool for loading images. Actual booting however
should be done by a separate OS loader application. For Linux, this
will be an in-kernel UEFI Stub. For Xen I would recommend taking the
Linux EFI stub code and doing the same thing. There really isn't a
need for a multiboot spec when you can rely on a runtime execution
environment for setting things up exactly as you want them.

Multiboot only makes sense to me when you need to rely on firmware or
something else out of your control to load the images in a particular
way.

g.

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