Re: [PATCH v2 22/23] x86: make Xen early boot code relocatable

[Andrew Cooper]

On 28/08/15 07:54, Jan Beulich wrote:
>
>> Therefore I am very much +1 get grub working.
> Then you kind of misunderstood: I'm not against getting grub2
> working (i.e. patches prior to this one are fine in principle). What
> I'm against is hacking around firmware+grub2 combinations not
> suitable for Xen's purposes (where one could argue which of the
> three is really at fault, and I'm far from convinced it's Xen).

Irrespective of the EFI angle, there are other good reasons for making
Xens boot code position-independent and able to be located elsewhere.

The region of memory between 0x10000 and 0x10fffe is at increased risk
of clobbering from buggy firmwares.  I have submitted bugfixes to Xen
before, and there are further investigations which didn't result in
anything upstream.

Moving the Xen text section out of this high risk region would make even
legacy boot more reliable.  Currently IMO it is a Xen bug that it
strictly must be placed at the 1MB boundary to boot.

~Andrew