Re: [Qemu-devel] OVMF, SeaBIOS & non-CSM based legacy boot

[Stefan Hajnoczi]

On Mon, Mar 21, 2011 at 9:17 PM, Michael Brown <address@hidden> wrote:
> On Monday 21 Mar 2011 21:06:24 Stefan Hajnoczi wrote:
>> On Mon, Mar 21, 2011 at 6:27 PM, Anthony Liguori <address@hidden>
> wrote:
>> > On 03/21/2011 01:14 PM, Jordan Justen wrote:
>> >> This weekend I spent some time working on loading SeaBIOS from OVMF to
>> >> start a legacy boot.  I was able to get x86&  x86-64 Linux to legacy
>> >> boot using this method.
>> >>
>> >> Unfortunately, (I think) it is not nearly as nice a having a true CSM.
>> >>  Basically, you have to decide at some point in the OVMF boot that you
>> >> want to legacy boot, and once you start SeaBIOS running, OVMF/UEFI
>> >
>> > Interesting.  How much time does OVMF add to the total boot time when
>> > taking this approach?
>> >
>> >> will never be in the picture again (until system reset).
>> >>
>> >> Contrast this to using a CSM where you can:
>> >> * Load a legacy option ROM (vbios, or disk rom),
>> >>   and use it during a UEFI boot
>> >
>> > Is there gPXE for UEFI yet?
>>
>> I have never tried it myself, but I think it should work.  CCed
>> Michael Brown to check.
>
> Yes, iPXE for UEFI exists and works.  Last tested by me about a week ago, on
> various IBM UEFI systems.
>
> Compared to a "legacy" BIOS network boot, you can't do anything very
> interesting with UEFI.  Features such as iSCSI, FCoE, AoE, HTTP all work with
> a "legacy" BIOS but not with UEFI.  A "legacy" BIOS network boot allows you to
> boot an operating system; a UEFI network boot only allows you to boot an EFI
> executable (which could be a second-stage OS loader).

Would it be possible to enable the more interesting things by
registering as a network device or block device with UEFI?  I don't
know much about UEFI but I seem to remember that you can do that
rather than being a pure bootloader that loads an EFI executable?

Stefan