Re: [Xen-devel] [PATCH v2 3/5] xen/x86: Migrate to boot_info structure

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-09-24 at 19:19 +0200, Daniel Kiper wrote:
> Break multiboot (v1) protocol dependency. It means that most of Xen code
> (excluding preloader) could be bootloader agnostic and does not need almost
> any knowledge about boot protocol. Additionally, we are able to pass all boot
> data to __start_xen() in one bucket without any side channels. I do not 
> mention
> that we are also able to easily identify boot data in Xen code.
> 
> Here is boot data flow for legacy BIOS platform:
> 
>  BIOS -> GRUB -> multiboot[12]* -> __reloc() -> MBD ->-\
>                                                        /
>         ------<------<------<------<------<------<-----
>          \
>           \
>            ---> __init_boot_info() -> boot_info_mb -> __start_xen() -> 
> boot_info
>           /
>  BIOS ->-/
> 
>   * multiboot2 is not implemented yet. Look for it in later patches.
> 
> Here is boot data flow for EFI platform:
> 
>   EFI -> efi_start() -> boot_info_efi -> __start_xen() -> boot_info
> 
> WARNING: ARM build could be broken by this patch.

The hypervisor is easy to cross compile, so please confirm and if so fix
it.

I use the cross compilers from
https://launchpad.net/linaro-toolchain-binaries 

See
http://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions#Cross_Compiling
 for more info.

> We need to agree boot_info
> integration into ARM. Personally I think that it is worth storing all data
> from any bootloader and preloader in boot_info on any architecture. This give
> a chance to share more code between architectures. However, every architecture
> should define its own boot_info (in relevant include/asm directory). Despite
> that it looks that some parts of it could be common, e.g.  modules data,
> command line arguments, boot loader name, EFI data, etc., even if types
> would not be the same. So, as it was stated above a lot of code could be
> shared among architectures.

As I think I've said before I'm happy to consider this in the future but
not for 4.5 at this stage. Please ensure that ARM at least still
compiles after this change.

Ian.


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