Re: [Xen-devel] [PATCH v16 7/9] x86: make Xen early boot code relocatable

[Doug Goldstein <cardoe@xxxxxxxxxx>]

On 4/13/17 9:11 AM, Daniel Kiper wrote:
> On Fri, Apr 07, 2017 at 05:23:33AM -0600, Jan Beulich wrote:
>>>>> On 21.02.17 at 20:19, <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 2 MiB and ends at ~5 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 and help boot loader to
>>> relocate image in proper way by suggesting, not requesting specific load
>>> addresses as it is right now, allowed address ranges. This patch does
>>> former.
>>> It does not add multiboot2 protocol interface which is done in "x86: add
>>> multiboot2 protocol support for relocatable images" patch.
>>>
>>> This patch changes following things:
>>>   - %esi register is used as a storage for Xen image load base address;
>>>     it is mostly unused in early boot code and preserved during C functions
>>>     calls in 32-bit mode,
>>>   - %fs is used as base for Xen data relative addressing in 32-bit code
>>>     if it is possible; %esi is used for that thing during error printing
>>>     because it is not always possible to properly and efficiently
>>>     initialize %fs.
>>>
>>> Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
>>
>> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> It looks that everything passed through test gate and landed in master.
> So, this way we have full multiboot2 support in Xen. This means that
> you can boot Xen using GRUB2 on EFI platforms.
> 
> I would like to thank everybody who helped me to make it happen.
> Especially Jan who patiently reviewed whole series many times
> and replied for my stupid questions.
> 
> Daniel
> 

Congrats Daniel.

-- 
Doug Goldstein

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