Re: [Xen-devel] [PATCH for-xen-4.5 v4 00/18] xen: Break multiboot (v1) dependency and add multiboot2 support

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.10.14 at 19:55, <konrad.wilk@xxxxxxxxxx> wrote:
> On 10/23/2014 12:04 PM, Jan Beulich wrote:
>>>>> On 23.10.14 at 17:50, <daniel.kiper@xxxxxxxxxx> wrote:
>>> OK, AIUI you suggest that I should parse all multiboot2 data in reloc.c
>>> and put all things in multiboot1 struct which lives on trampoline. Then
>>> I should add global variables for EFI_HANDLE and EFI_SYSTEM_TABLE somewhere
>>> in x86_64.S and initialize them from reloc.c. After that I should call
>>> efi_start() immediately after reloc() if Xen runs on EFI platform.
>>
>> I wouldn't call this "parse", but beyond that it sounds roughly right.
>> Whether you need global variables or can find some other
>> mechanism to propagate the EFI specific things is secondary.
> 
> This seems to lead to more spaghetti code - why not make it a more nice 
> mechanism right away? Is that because you want to have this in a 
> separate "bin" in case it has bugs and won't influence the rest of the code?
> 
> And then later if it all works then integrate and cleanup? Or skip that 
> altogether?

Whether and how much cleanup would subsequently be desirable
can only be reasonably told at the point we know/see what is
needed for MB2 support. Right now the re-write looks more to be
for the sake of doing a re-write. Please keep in mind that unified
code paths and data fields aren't always advantageous, as the
sharing can also lead to subtle bugs for one of the handled cases.

Jan


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