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Re: [Xen-devel] 4.3 Planning: Taking stock

On Wed, Jan 23, 2013 at 05:00:26PM +0000, Jan Beulich wrote:
> >>> On 23.01.13 at 17:52, George Dunlap <George.Dunlap@xxxxxxxxxxxxx> wrote:
> >> * Xen EFI feature: dom0 able to make use of EFI run-time services
> >>
> > 
> > Daniel Kiper is already working on this, but has just started.  The issue
> > (as I understand it) is that if there are systems where the ACPI tables are
> > only discoverable via EFI, then Xen+pvops will not be able to boot if pvops
> > doesn't have EFI run-time support.  The following version of Xen won't come
> > out until probably Q2 2014, and won't hit distros probably until 6 months
> > after that.
> > 
> > Given that, what do we think is the likelihood of such systems cropping up
> > in that timeframe?  If the answer is anything other than "very low", I
> > think that as a strategic measure, this one is probably important enough to
> > slip the schedule a little bit if necessary.
> Except that this ought to be marked (external) in the first place:
> The hypervisor support is all there (otherwise our kernels wouldn't
> have been successfully booting on EFI for well over a year), and
> hence this work shouldn't really have any impact on the schedule.
> The one feature here that requires work in our tree is to be able
> to boot via grub.efi (irrespective of how little I personally like that);
> I'm not sure Daniel was also planning to look into that part.

CC-ing Daniel here.

My recollection is that from the Linux PV dom0 standpoint it does not matter
what the bootloader is. It ends up with the information from the hypervisor
 - and it is the hypervisor that is either called (xen.efi) or it (the 
gets the information from an EFI-enabled bootloader (grub*.efi).

Either way, the Linux kernel gets called via XEN_ELFNOTE_ENTRY entry and
it would be responsible for making the proper hypercalls to populate
the bootparams and the efi tables so that the generic code can
continue on with the proper information.

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