Re: [Xen-users] usage questions for GRUB2 chainloader workaround when booting Xen 4.5 on UEFI

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Sat, 2015-03-28 at 08:22 -0700, lyndat3@xxxxxxxxxxxxx wrote:
> > Would this GRUB2 menuentry work?
> > 
> >     menuentry 'Xen EFI' {
> >             insmod part_gpt
> >             insmod search_fs_uuid
> >             insmod chain
> >             search --no-floppy --fs-uuid 94C3-29F3
> >             chainloader /EFI/XEN/xen.efi
> >     }
> 
> 
> A bit more info.  The stanza above did not work.  Boot aborts with 'disk not 
> found'.
> 
> Attempting to exactly specify the drive, where
> 
>       mount | grep boot
>               /dev/md0 on /boot type ext4 
> (rw,noatime,journal_checksum,data=ordered)
>               /dev/sdg2 on /boot/efi type vfat 
> (rw,relatime,fmask=0002,dmask=0002,allow_utime=0020,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro)
> 
>       blkid /dev/md0
>               /dev/md0: UUID="4d85d86e-72c3-996d-1284-8e374646886c" 
> TYPE="ext4" 
> 
>       mdadm -Es | grep md/0
>               ARRAY /dev/md/0  metadata=1.0 
> UUID=b74544cc:8454cc33:6d44b6c5:86c58355 name=xen01:0
> 
>       ls -al /dev/disk/by-id/md-uuid-b74544cc:8454cc33:6d44b6c5:86c58355
>               lrwxrwxrwx 1 root root 9 Mar 27 21:44 
> /dev/disk/by-id/md-uuid-b74544cc:8454cc33:6d44b6c5:86c58355 -> ../../md0
> 
> and blindly cribbing parts from the default grub nonn-xen menuentry, which 
> boots fine, I also tried
> 
>       menuentry 'Xen EFI' {
>               insmod part_gpt gpt
>               insmod diskfilter mdraid1x
>               insmod ext2
>               insmod search_fs_uuid
>               insmod chain
>               set root='mduuid/b74544cc8454cc336d44b6c586c58355'
>               if [ x$feature_platform_search_hint = xy ]; then  
>                       search --no-floppy --fs-uuid --set=root 
> --hint='mduuid/b74544cc8454cc336d44b6c586c58355'  94C3-29F3
>               else
>                       search --no-floppy --fs-uuid --set=root 94C3-29F3
>               fi
>               search  --no-floppy --fs-uuid 94C3-29F3
>               chainloader /EFI/XEN/xen.efi
>       }
> 
> The boot still fails.  Disk not found.

I'm not sure what's going wrong here, but my advice would be to play
around at the grub prompt until you figure it out, it has tab completion
etc and will be a lot faster to debug that constantly rebooting. e.g.
try typing "set root=(" and then press tab to see the options, then try
your insmods and try again etc.

Since you are chainloading you might find it easier to put Xen in
your /boot rather than on you ESP, since all the existing stanzas will
be tailored towards loading stuff from /boot.

Lastly, I'm not 100% sure if chainloading xen.efi like this is supposed
to work. The docs talk about adding it directly to the UEFI boot menu
not going via grub. I suppose the answer depends on what state chainload
leaves UEFI in (i.e. boot services still enabled or not).

Ian.


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