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

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Thu, Apr 13, 2017 at 02:43:22PM -0500, Doug Goldstein wrote:
> 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.

Thank you.

Daniel

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel