Created attachment 179951
dmesg of 4.0.5 vanilla kernel with iommu=on

`grep -i -e dmar -e iommu` is below

[    0.000000] Command line: BOOT_IMAGE=/vmlinuz-linux-vanilla root=UUID=8445003e-6304-4d86-b970-2afa31781a9b rw intel_iommu=on
[    0.000000] ACPI: DMAR 0x00000000DAC6CED0 0000B8 (v01 INTEL  BDW      00000001 INTL 00000001)
[    0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-linux-vanilla root=UUID=8445003e-6304-4d86-b970-2afa31781a9b rw intel_iommu=on
[    0.000000] Intel-IOMMU: enabled
[    0.107086] dmar: Host address width 39
[    0.107098] dmar: DRHD base: 0x000000fed90000 flags: 0x0
[    0.107123] dmar: IOMMU 0: reg_base_addr fed90000 ver 1:0 cap c0000020660462 ecap f0101a
[    0.107138] dmar: DRHD base: 0x000000fed91000 flags: 0x1
[    0.107154] dmar: IOMMU 1: reg_base_addr fed91000 ver 1:0 cap d2008c20660462 ecap f010da
[    0.107169] dmar: RMRR base: 0x000000dbe7b000 end: 0x000000dbe89fff
[    0.107179] dmar: RMRR base: 0x000000dd000000 end: 0x000000df1fffff
[    0.107191] IOAPIC id 8 under DRHD base  0xfed91000 IOMMU 1
[    0.685402] DMAR: No ATSR found
[    0.685642] IOMMU: dmar0 using Queued invalidation
[    0.685651] IOMMU: dmar1 using Queued invalidation
[    0.685662] IOMMU: Setting RMRR:
[    0.685694] IOMMU: Setting identity map for device 0000:00:02.0 [0xdd000000 - 0xdf1fffff]
[    0.686154] IOMMU: Setting identity map for device 0000:00:14.0 [0xdbe7b000 - 0xdbe89fff]
[    0.686215] IOMMU: Setting identity map for device 0000:00:1a.0 [0xdbe7b000 - 0xdbe89fff]
[    0.686268] IOMMU: Setting identity map for device 0000:00:1d.0 [0xdbe7b000 - 0xdbe89fff]
[    0.686308] IOMMU: Prepare 0-16MiB unity mapping for LPC
[    0.686329] IOMMU: Setting identity map for device 0000:00:1f.0 [0x0 - 0xffffff]
[    0.847930] dmar: DRHD: handling fault status reg 2
[    0.848264] dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr fffe0000 
               DMAR:[fault reason 02] Present bit in context entry is clear
[    1.161006] dmar: DRHD: handling fault status reg 3
[    1.161963] dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr fffe0000 
               DMAR:[fault reason 02] Present bit in context entry is clear
[    6.159656] dmar: DRHD: handling fault status reg 2
[    6.160750] dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr fffe0000 
               DMAR:[fault reason 02] Present bit in context entry is clear
[    6.472980] dmar: DRHD: handling fault status reg 3
[    6.473513] dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr fffe0000 
               DMAR:[fault reason 02] Present bit in context entry is clear
[   11.471329] dmar: DRHD: handling fault status reg 2
[   11.471661] dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr fffe0000 
               DMAR:[fault reason 02] Present bit in context entry is clear
[   11.784476] dmar: DRHD: handling fault status reg 3
[   11.785472] dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr fffe0000 
               DMAR:[fault reason 02] Present bit in context entry is clear
[   16.783038] dmar: DRHD: handling fault status reg 2
[   16.783646] dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr fffe0000 
               DMAR:[fault reason 02] Present bit in context entry is clear
[   74.080032] [drm] DMAR active, disabling use of stolen memory