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Re: [Xen-devel] Xen 4.3 development update, and stock-taking

>>> On 17.01.13 at 14:58, George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:
> On 17/01/13 12:51, Jan Beulich wrote:
>>> On 17/01/13 09:09, Jan Beulich wrote:
>>>> But of course pv-ops Linux continues to lack EFI support altogether.
>>> OK, so I think the description needs an update, then.  For Xen to be
>>> fully featured, I think it would need all of the following:
>>> * An EFI-bootable dom0 (this should be done, right?)
>> "Done" in the sense of todo for pvops (our kernels have been able
>> to for quite a long while).
> Just to be clear here: are you saying that there is no way to boot Xen 
> directly from EFI with a pvops kernel?  if so, that seems like a pretty 
> big deal to me...

It depends on the system: Those ones where legacy methods still
allow finding namely ACPI tables would allow booting. On ones
where those tables can be found only by consulting EFI, booting
is possible, but you'd generally end up without PCI interrupts
(which to me is almost the same as "doesn't boot").

>>> * Xen able to use EFI boot-time services (?)
>> Sure, that's how things work. Otherwise we wouldn't boot at
>> all from EFI. The one extra thing that some people had asked
>> for was to be able to also properly boot Xen via grub.efi.
> Doesn't this already work?

Not generally, the same restriction as above applies.

>>> * Xen able to detect the existence of a signed Linux binary, and leave
>>> EFI boot-time services enabled for dom0 to use when appropriate
>> No. We can't leave bot services enabled, and we also don't
>> need to. The model is that only the Dom0 kernel binary needs
>> validation at the boot loader level. Everything else will be
>> done in the kernel (including initrd validation, or really the
>> parts of it that need validation).
> As I understood it, the Ubuntu bootloader will not require an image to 
> be signed to boot.

Yes - the plan is to decide whether booting securely by picking
to boot with or without the shim. All layers above have to
react accordingly. However, it is my understanding that if you
use the shim and your kernel isn't signed, boot will fail.

>  Nonetheless, Ubuntu are still signing their kernel 
> images, because they want the kernel to be able to play some fancy 
> tricks for which they need boot-time services.  (I think this is 
> something to do with making it easy to upload your own keys.) Full EFI 
> functionality for Xen would include the ability to do this as well.

Yes, because you particularly need access to the EFI variables
from the kernel. Which in turn requires an EFI-enabled kernel.


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