I am getting random screen freezes in which the mouse still moves around but the mouse button and keyboard do not work. If youtube is playing the music continues on. Before a freeze everything works fine. It may work for 1 minute or 1 hour after a reboot and a freeze does not seem to depend on what desktop application I am running.

When this happens I always see the following in the log files.

kernel: DMAR: DRHD: handling fault status reg 2
Jan 24 16:41:19 kernel: DMAR: INTR-REMAP: Request device [[00:00.1] fault index 2b
                                                    INTR-REMAP:[fault reason 38] Blocked an interrupt request due to source-id verification failure
kernel: DMAR: INTR-REMAP: Request device [[00:00.0] fault index 27
                                                    INTR-REMAP:[fault reason 38] Blocked an interrupt request due to source-id verification failure
Jan 24 16:41:20 /usr/libexec/gdm-x-session[2491]: Successfully activated service 'org.gnome.evolution.dataserver.Calendar7'
Jan 24 16:41:20 kernel: DMAR: DRHD: handling fault status reg 202
Jan 24 16:41:20 kernel: DMAR: INTR-REMAP: Request device [[00:00.1] fault index 2b
                                                    INTR-REMAP:[fault reason 38] Blocked an interrupt request due to source-id verification failure

I can ssh in. I need to reboot to get things working again.

Any idea what this means and how to fix it?

The system is new:
Dell Precision Tower 7910
Dual Intel Xeon E5-2687W v3
64GB (8x8GB)
1TB SATA 7.2k
 AMD FirePro W4100 2GB (4 mDP)
 LSI SAS 3008

I'm using the standard X driver which is listed as RADEON
and under system details: Gallium 0.4 on AMD Cape Verde. 

Thanks

John