Re: UEFI ExitBootServices

[John Nemeth <jnemeth%cue.bc.ca@localhost>]

On Sep 6,  3:43am, Emmanuel Dreyfus wrote:
} 
} I am working on multiboot for EFI bootstrap, the target being to boot
} xen.
} 
} This requires implementing the multiboot2 protocol [1]. I did most of
} it, and it is able to boot Xen with legacy BIOS boostrap boot(8).
} However, using EFI bootstrap bootx64.efi success is not there yet.
} 
} Adding debug messages in Xen, I know the hypervisor starts up, and I
} have somes traces up to the UEFI ExitBootServices call. It fails:
} Cannot exit boot services: ErrCode: 0x8000000000000002
} 
} Anyone has some hints about this? Why could this fail? A search on
} internet suggests that ExitBootServices requires the memory map, and
} that getting it modifies the memory map, hence it should be done twice,
} but this is exactly what Xen does. ExitBootServices still fails on the
} second call.

     The answer is to check the spec.  I just downloded the latest
version from uefi.org (I had a slightly older version of it).  The
only return codes listed for ExitBootServices are success and
invalid parameter.  The latter will be given if MapKey is incorrect.

     BTW, can you summarize the difference between multiboot and
multiboot2?

} [1] https://www.gnu.org/software/grub/manual/multiboot2/multiboot.html
} 
}-- End of excerpt from Emmanuel Dreyfus