Comment 3 for bug 1555786

I can confirm that 4.5 final and 4.5-rc7 fail to boot on a 32bit guest on my setup as well. I am seeing an I/O error on the disk. Booting back into a 15.10 kernel, the disk is automatically fsck'd and boots fine. Going back to a mainline kernel, I get the I/O error again.

I'll test some of the other 4.5 release candidates to find the last good one and first bad one. We can then bisect to find the commit that introduced this.