Re: [Xen-devel] EFI and multiboot2 devlopment work for Xen

[Konrad Rzeszutek Wilk]

On Tue, Oct 22, 2013 at 04:22:38PM +0100, Ian Campbell wrote:
> On Tue, 2013-10-22 at 15:24 +0100, Ian Campbell wrote:
> > On Tue, 2013-10-22 at 10:09 -0400, Konrad Rzeszutek Wilk wrote:
> > 
> > > So it can be booted the same way as xen.efi. But my understanding is
> > > that folks prefer a bootloader instead of loading the bzImage in an
> > > NVRAM of a platform with pre-set parameters. Hence that mechanism
> > > is not used by the majority of users.
> > 
> > My understanding is that they prefer a bootloader which can launch Linux
> > as a PE/COFF image, i.e. the linuxefi thing.
> 
> What I'm trying to say here is that from the xen.efi or linux.efi point
> of view it can't tell if it was launched directly from the EFI shell or
> by some intermediate bootloader (i.e. by grub2's linuxefi command).

It can (at least in Linux). There are two entry points in the Linux kernel
and - one when it is launched from 'linuxefi' (See efi_stub_entry in 
arch/x86/boot/compressed/head_64.S), the other when it is launched
from an EFI shell - see efi_pe_entry in arch/x86/boot/compressed/head_64.S.