Re: [Xen-devel] [PATCH 2 of 3] Enable UEFI BIOS(OVMF) support in Xen-unstable HVM

[Jordan Justen <jljusten@xxxxxxxxx>]

On Tue, Aug 9, 2011 at 13:32, Keir Fraser <keir.xen@xxxxxxxxx> wrote:
> On 09/08/2011 21:19, "Jordan Justen" <jljusten@xxxxxxxxx> wrote:
>
>>>> I suspect ovmf-x64 is a superset of the capabilities of ovmf-ia32 (e.g.,
>>>> ability to boot UEFI-bootable 64-bit OSes?). If so, we should only support
>>>> one config option -- "ovmf" -- and have hvmloader auto-load the appropriate
>>>> OVMF build, based on CPUID.long_mode.
>>>
>>> Yes, that's the sort of thing I was getting at.
>>
>> The IA32 firmware is used for IA32 UEFI operating systems, and the X64
>> firmware is used for X64 operating systems.
>
> I assume a native box would only have one UEFI firmware, and that would be
> X64 on an x86/64 box. You must still be able to boot IA32 operating systems
> on the X64 firmware, right?

Yes, it could technically be booted, if the OS loader was an X64
application that transitioned to IA32 before starting the OS kernel.

But, the IA32 OS would then have issues if it wanted to call UEFI
runtime services, which would be X64.

>> X64 is somewhat more commonly used on modern systems.
>>
>> There could be an auto-detect mode for the default of IA32 or X64
>> based on the installed CPU, but there might still be a case where
>> someone would prefer to run OVMF IA32 on an X64 processor.
>
> Such as?

If you had an IA32 UEFI OS, it would be better to boot the IA32 OVMF
for the reason mentioned above.

-Jordan

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