Re: [Xen-devel] Relocatable Xen early boot code

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.06.15 at 15:51, <daniel.kiper@xxxxxxxxxx> wrote:
> On Fri, Jun 12, 2015 at 01:08:41PM +0100, Jan Beulich wrote:
>> >>> On 12.06.15 at 13:14, <daniel.kiper@xxxxxxxxxx> wrote:
>> > Here I do not want to discuss GRUB2 and multiboot2 protocol support details
>> > for relocatable images. It is not needed. It is sufficient to know that it
>> > is able to put loaded image anywhere in available memory below 4 GiB. 
> Loaded
>> > image is informed about its base address according to multiboot2 protocol
>> > via
>> > special tag. This is new feature not available in upstream GRUB2. I work on
>> > upstreaming it in parallel. Relevant patches will be posted together with
>> > Xen patches.
>>
>> Before going into any detail on what you write later on - if this isn't in
>> upstream grub2, why can't you do what you want to do first without
>> another change needed in the boot loader? In which case, if I'm reading
>> this correctly, you wouldn't need our boot code to become relocatable
>> either.
> 
> multiboot protocol (any version) puts image at address as it requests.
> Always, without any exception. So, in our case starting from 1 MiB.
> On legacy BIOS platforms it works. However, on EFI platforms it is not
> always possible because sometimes some parts of EFI boot/runtime services
> live somewhere around 1 MiB. So, first of all we must change multiboot
> protocol behavior (in our case version 2 because it is more flexible)
> and learn it to relocate images into free memory region. On the other
> hand we must learn Xen early boot code to live at different addresses.
> We must do all this changes in GRUB2 and in Xen in parallel.

Right, I now recall (the huge time difference between individual
steps is of course kind of problematic here).

Jan


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