Re: Xen 4.3 development update, and stock-taking

[George Dunlap <george.dunlap@eu.citrix.com>]

On 17/01/13 16:49, Jan Beulich wrote:
>> In that case, it would be good if, sometime in the next month or two,
>> someone could take a look at exactly what these "quirks" are that Linux
>> needs boot services for, and figure out whether we are likely to need
>> them.  I'll put that in a sort of "call to action", along with any other
>> important features not currently on track to make it into 4.3.
> I know that code pretty well meanwhile, and I'm unaware of
> quirks requiring boot services access.

Interesting.  Well, maybe I should just ask Colin which changes he was 
talking about.  It's always possible they're in the Ubuntu patchqueue 
and haven't been upstreamed yet.  If it really does have to do with the 
framebuffer, it might just have to do with the Ubuntu splash screen, 
which will be replaced once X.org comes up anyway.

> Also, I was slightly wrong in saying it is always Linux to exit boot
> services: That's the case when booted without boot loader
> (i.e. using the EFI_STUB mechanism). Otherwise it's the boot
> loader doing so. But you remember that so far we don't really
> support booting from EFI with boot loader, so we ought to
> always compare ourselves to that stub mechanism.

To decide what "Xen has full support for EFI" means, we ought to compare 
ourselves with anywhere Linux can boot.  So if there is some 
functionality for Ubuntu when booting "EFI -> shim -> bootloader -> 
Linux", then "full support" means having the same functionality when 
booting "EFI -> shim -> bootloader -> Xen -> Linux".

Not all of that functionality needs to be implemented -- we may decide 
that "full support" isn't really worth our while (e.g. if it's a lot of 
work just to make Ubuntu's splash screen function properly instead of 
falling back to text mode).  But it needs to be a conscious decision 
made for specific reasons, not because we just didn't think about it.

  -George