Re: New Xen boot infrastructure proposal

[Daniel Kiper <daniel.kiper@oracle.com>]

On Wed, May 22, 2013 at 04:41:31PM +0100, Ian Campbell wrote:

[...]

> In that case my question (which I think others have raised) is why does
> this need to be a complex extensible protocol at all? The two halves
> here must surely be upgraded in sync and so both sides can be changed
> whenever the data needs expanding. i.e. this is just struct boot_info,
> which perhaps contains "struct arch_boot_info arch;"
>
> Or perhaps I've just read more into what you are proposing than you were
> actually proposing.

MBI structure which is passed to __start_xen() is strictly defined and
could not be changed. It worked very nice once but now it is not true.
It does not have enough place to pass eny extra information from other
bootloaders (in this case multiboot2 protocol aware) and there are some
members which are not used. In that case we must have e.g. global variables
or other solution to pass that extra info. That is why I think we should
build new struture which will replace MBI. It should have only data which
is used by Xen. This way we could add in the future any extra members if we
require it and we would not be so strictly bound to any boot protocol.

However, I do not insist on the split between arch dependent and
independent stuff. I know this is disputable. However, I posted
that idea because I was not sure that soultion will fit.
I just wanted to dicuss pros and cons of this split too.

Daniel