[Pkg-xen-devel] Bug#785187: Bug#785187: xen-hypervisor-4.5-amd64: Option ucode=scan is not working

[Ian Campbell]

On Tue, 2015-05-19 at 13:31 +0200, Stephan Seitz wrote:
> On Fri, May 15, 2015 at 08:26:42AM +0100, Ian Campbell wrote:
> >Here's an idea. First extract the real initrd from the back half of the
> >initrd:
> >        ijc at dagon:tmp$ cat /boot/initrd.img | ( cpio -t >&2 ; cat ) > initrd.real
> >        kernel
> >        kernel/x86
> >        kernel/x86/microcode
> >        kernel/x86/microcode/GenuineIntel.bin
> >        16 blocks
> >        ijc at dagon:tmp$ file initrd.real
> >        initrd.real: gzip compressed data, last modified: Sun Apr 19 16:31:17 2015, from Unix
> >        ijc at dagon:tmp$ zcat initrd.real | cpio -t | head -n 5
> >        .
> >        etc
> >        etc/ld.so.conf.d
> >        etc/ld.so.conf.d/fakeroot-x86_64-linux-gnu.conf
> >        etc/ld.so.conf.d/x86_64-linux-gnu.conf
> >
> >Now you can experiment with regenerating the ucode bit with whatever
> >commands are recommended and reconcatenating the two. If that works then
> >we know there is some incompatibility between iucode-tools's output and
> >Xen's cpio reader (could be a bug in either or both I think).
> 
> All right. Can you please provide some commands how to create and 
> reconcatenate the two initrds? I don’t have any experience with cpio.

The reconcatenate bit is easy, just:
   $ cat initrd.ucode initrd.real > initrd.img
With initrd.real extracted above.

initrd.ucode creation I'm a little unsure about but something like:

$ mkdir initrd.ucode.tree
$ cd initrd.ucode.tree
$ cat /boot/initrd.img | cpio -id
$ find 
.
./kernel
./kernel/x86
./kernel/x86/microcode
./kernel/x86/microcode/GenuineIntel.bin
$ find | cpio -o -H newc > ../initrd.ucode

Is what I think is required/expected.

BTW, could you please post the output "xl dmesg" for the failing case, I
should have asked for that right at the start in case it contains
anything of use.

Ian.