Am running fedora 4.6.3 on another identical dell laptop, and havent seen this problem. Upgraded a second laptop to 4.7.6 and then to 4.7.7, and both of those releases on the second laptop are failing and halting at boot (most of the time) at the Booting SMP configuration, usually after CPU #3. Applications on the laptops use a hardware device on thunderbolt that use DMA access to support high speed data transfers.

I built kernels on both laptops to include following kernel configuration parameters (via make menuconfig):
enabled VFIO Non-Privileged userspace driver framework, enabled VFIO PCI support for PCI devices,
disabled VFIO No-IOMMU support,
disabled VFIO PCI support for VGA devices.
Under the IOMMU Hardware Support:
enabled Support for Interrupt Remapping,
enabled Support for Intel IOMMU using DMA Remapping Devices, enabled Support for Shared Virtual Mmeory with Intel IOMMU,
enabled Intel DMA Remaping Devices by default

The boot failures occur regardless of whether the device is plugged in or not. I used the same kernel configuration on both laptops. Did not see any specific warnings or errors during kernel builds.

Looking for suggestions on why the boot failures are occurring, and how to avoid them without disabling SMP altogether, which does make the problem go away (as well as the multicore processing.)

Dan

if you are using fedora 4
you have a major problem

it is 20 versions and 11 years out of date

Apologies for confusing release numbers. It is Fedora 24, with kernel versions 4.6.3 and 4.7.7.

Dan

Simple first step would be to ensure your devices are all up-to-date - see this Archlinux wiki entry. Especially the firmware note.

No experience with thunderbolt, just passing on what I found.