Re: [Xen-devel] Building 32-bit xen.efi for 32-bit EFI platforms

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.11.14 at 15:59, <zhuanchen@xxxxxxxxx> wrote:
> I am wondering whether it's possible to build 32-bit xen.efi for the
> 32-bit EFI platform? One way of building xen.efi I learnt is to make
> the binutils configured with the x86_64-pep emulation (according to
> the document http://xenbits.xenproject.org/docs/unstable/misc/efi.html).
> The resulted xen.efi is 64-bit mode. Is it possible to build xen.efi
> as the 32-bit mode?
> 
> The reason for this question is due to my effort of installing Xen on
> the Asus Transformer Book T100, which is one of the Bay Trail Atom
> (64-bit processors) tablets shipped with 32-bit EFI firmware. This
> requires the support of the 32-bit EFI bootloader. Such platforms seem
> to become common and Linux kernel from 3.15 also provides the EFI
> mixed mode to support 64-bit kernels running from 32-bit EFI firmware.

This mixed mode support is kind of crippled, as it suppresses all use
of runtime services. But that aside, as others said what you ask for
is currently not possible - feel free to submit patches to improve the
situation, but be aware that a number of assumptions of being 64-bit
are currently made in the boot loader code, so you'd have to do
careful code review first to spot all places needing adjustment.

Jan


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