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Re: [Xen-devel] Xen, Linux and EFI.

On Wed, Jul 11, 2012 at 4:45 PM, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:

There has been some discussion about EFI and SecureBoot and such.

Most of the time I get questions in the form of "How do I get Fedora 17
with Xen to do EFI", I am going to concentrate on Fedora, but I think
this applies to other distros too.

>From my reading (I hadn't actually tried EFI yet), there are two ways
to bootup a system:

 - Using grub2.efi. Grub2 does the EFI API calls and calls the Xen hypervisor
   as if there were no EFI. This means no need for the EFI calls from
   Linux or Xen are required).

 - Using xen.efi. Xen can be built as a PE (Portable Executable) and it can
   boot as an EFI image. Naturally you also need to provide a configuration
   file and here are the details on it:

   And you would also need to configure the EFI nvram to execute xen.efi
   instead of grub2.efi.

   For the Linux side, the kernel needs to make new EFI variant hypercalls.
   Currently the SLES kernel is capable of it. The upstream Linux kernel
   cannot do it. There were patches proposed for it:

Does the Linux side dom0 kernel changes need to be done irrespective of the
two options above ? or does it apply only for booting with xen.efi ?

I spent a week trying to get Xen boot with grub2.efi (ubuntu 12.04).
I ended up getting "Not enough memory to relocate domain 0".

So I presume that the dom0 kernel EFI support needs to be done for both
cases (grub2.efi and xen.efi) ?

Additional info:
 Hardware: IBM System X server.

 It appeared that when booting xen under grub2.efi, xen was picking up a e-801 map
 instead of the e-820 map that was on the system. I forced xen code to a multiboot
 e-820 map instead of the native one ( based on a forum post I saw).
 That didnt help much.

So I ended up booting with a SLES kernel. Not even sure if opensuse 12.1 will work.

   which were mostly ports of how SLES did it (And they should reflect
   the proper ownership, which they don't have right now).

   The EFI maintainer (Matthew) commented
   that he would like a better abstraction model for it. Mainly to
   push those calls deeper down (so introduce the registration in the
   the efi_calls). Or perhaps by providing in boot_params.efi_info.efi_systab
   a finely crafted structure pointing to Linux functions that would
   do the hypercalls.

And there you have it. In other words it needs somebody willing to
look at the patches as a baseline and do some exciting new work.
I sadly don't have right now the time to address this :-(

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