We've had a rash of reports of kernels not booting on some Skylake based machines recently.  After working these, we've determined that a recent Intel microcode update somehow conflicts with something in the system firmware for these machine, causing a complete failure to boot after grub loads the kernel.

Some of these systems have a firmware update (BIOS/UEFI) that restores functionality even with the microcode being loaded.  Other systems do not yet at this time.  If you experience a boot hang on a Skylake based machine, you can try and determine if the microcode is at fault by specifying 'dis_ucode_ldr' on the kernel command line.  That prevents the kernel from loading the microcode during the early boot.

The issue is mostly being tracked here: https://bugzilla.redhat.com/show_bug.cgi?id=1353103

Some of the machines involved are:

Lenovo Thinkpad T460
Lenovo Thinkpad x260
Lenovo Yoga 260
ASUS Zenbook UX305CA
Samsung Notebook 9

josh