Re: [Xen-devel] [PATCH 1 of 2] Add the support for Xen to include OVMF UEFI support and directly use it

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.02.12 at 16:37, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Thu, 2012-02-23 at 14:48 +0000, Jan Beulich wrote:
>> >>> Attilio Rao <attilio.rao@xxxxxxxxxx> 02/23/12 11:18 AM >>>
>> >On 23/02/12 10:07, Ian Campbell wrote:
>> >> On Wed, 2012-02-22 at 19:17 +0000, Attilio Rao wrote:
>> >> Can you confirm that you need an OVMF which matches the OS bit-width you
>> >> are installing. i..e that there is no support for booting a 32 bit EFI
>> >> OS (or bootloader, shell, whatever it is called) on a 64 bit OVMF?
>> >
>> >I didn't test this case, really, but I would think OVMF-64 / OS-32 could 
>> >possibly work.
>> 
>> Native EFI requires bit-matched OS loaders,
> 
> Is that a shortcoming of EFI generally or just this implementation?

I'd assume more the former.

> Surely people don't reflash their "BIOS" to be able to run a 32 vs 64
> bit OS? Or do most OSes (even 32 bit ones) have a 64 bit loader capable
> of loading a 32 bit OS?

When I asked the same question, I was told that the assumption is that
on modern (read: UEFI) systems people aren't expected to run 32-bit
OSes.

And no, I don't think any 32-bit OS comes with a 64-bit bootloader.
Furthermore, to make EFI really work, such an OS would also need
64-bit stubs to call the EFI services - not something that's realistically
going to happen I would think.

If anything, I would have expected that things could work out the
other way around: A 64-bit OS having a 32-bit loader and 32-bit
stubs (which is how we implemented this when, on x86, there was
no 64-bit EFI yet).

Jan


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