I have a Ryzen 7 1700 on an X370 Taichi running Fedora 25 with Kernel 4.10.17-200. The 980 Ti is successfully claimed by the vfio-pci driver and I can pass it to the vm. I think my main problem is my libvirt xml file, but I'm not sure what exactly I did wrong. The IOMMU groups are the following:
IOMMU Group 0 00:01.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1452]
IOMMU Group 10 00:18.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1460]
IOMMU Group 10 00:18.1 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1461]
IOMMU Group 10 00:18.2 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1462]
IOMMU Group 10 00:18.3 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1463]
IOMMU Group 10 00:18.4 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1464]
IOMMU Group 10 00:18.5 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1465]
IOMMU Group 10 00:18.6 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1466]
IOMMU Group 10 00:18.7 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1467]
IOMMU Group 11 03:00.0 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD] Device [1022:43b9] (rev 02)
IOMMU Group 11 03:00.1 SATA controller [0106]: Advanced Micro Devices, Inc. [AMD] Device [1022:43b5] (rev 02)
IOMMU Group 11 03:00.2 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:43b0] (rev 02)
IOMMU Group 11 04:00.0 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:43b4] (rev 02)
IOMMU Group 11 04:02.0 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:43b4] (rev 02)
IOMMU Group 11 04:03.0 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:43b4] (rev 02)
IOMMU Group 11 04:04.0 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:43b4] (rev 02)
IOMMU Group 11 06:00.0 SATA controller [0106]: ASMedia Technology Inc. ASM1062 Serial ATA Controller [1b21:0612] (rev 02)
IOMMU Group 11 07:00.0 PCI bridge [0604]: ASMedia Technology Inc. Device [1b21:1184]
IOMMU Group 11 08:01.0 PCI bridge [0604]: ASMedia Technology Inc. Device [1b21:1184]
IOMMU Group 11 08:03.0 PCI bridge [0604]: ASMedia Technology Inc. Device [1b21:1184]
IOMMU Group 11 08:05.0 PCI bridge [0604]: ASMedia Technology Inc. Device [1b21:1184]
IOMMU Group 11 08:07.0 PCI bridge [0604]: ASMedia Technology Inc. Device [1b21:1184]
IOMMU Group 11 09:00.0 Network controller [0280]: Intel Corporation Device [8086:24fb] (rev 10)
IOMMU Group 11 0b:00.0 Ethernet controller [0200]: Intel Corporation I211 Gigabit Network Connection [8086:1539] (rev 03)
IOMMU Group 11 0c:00.0 PCI bridge [0604]: ASMedia Technology Inc. ASM1083/1085 PCIe to PCI Bridge [1b21:1080] (rev 04)
IOMMU Group 11 0d:04.0 Multimedia audio controller [0401]: C-Media Electronics Inc CMI8788 [Oxygen HD Audio] [13f6:8788]
IOMMU Group 12 0f:00.0 VGA compatible controller [0300]: NVIDIA Corporation GM200 [GeForce GTX 980 Ti] [10de:17c8] (rev a1)
IOMMU Group 12 0f:00.1 Audio device [0403]: NVIDIA Corporation GM200 High Definition Audio [10de:0fb0] (rev a1)
IOMMU Group 13 10:00.0 VGA compatible controller [0300]: NVIDIA Corporation GP108 [10de:1d01] (rev a1)
IOMMU Group 13 10:00.1 Audio device [0403]: NVIDIA Corporation Device [10de:0fb8] (rev a1)
IOMMU Group 1 00:01.3 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:1453]
IOMMU Group 2 00:02.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1452]
IOMMU Group 3 00:03.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1452]
IOMMU Group 4 00:03.1 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:1453]
IOMMU Group 5 00:03.2 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:1453]
IOMMU Group 6 00:04.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1452]
IOMMU Group 7 00:07.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1452]
IOMMU Group 7 00:07.1 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:1454]
IOMMU Group 7 11:00.0 Non-Essential Instrumentation [1300]: Advanced Micro Devices, Inc. [AMD] Device [1022:145a]
IOMMU Group 7 11:00.2 Encryption controller [1080]: Advanced Micro Devices, Inc. [AMD] Device [1022:1456]
IOMMU Group 7 11:00.3 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD] Device [1022:145c]
IOMMU Group 8 00:08.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:1452]
IOMMU Group 8 00:08.1 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:1454]
IOMMU Group 8 12:00.0 Non-Essential Instrumentation [1300]: Advanced Micro Devices, Inc. [AMD] Device [1022:1455]
IOMMU Group 8 12:00.2 SATA controller [0106]: Advanced Micro Devices, Inc. [AMD] FCH SATA Controller [AHCI mode] [1022:7901] (rev 51)
IOMMU Group 8 12:00.3 Audio device [0403]: Advanced Micro Devices, Inc. [AMD] Device [1022:1457]
IOMMU Group 9 00:14.0 SMBus [0c05]: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller [1022:790b] (rev 59)
IOMMU Group 9 00:14.3 ISA bridge [0601]: Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge [1022:790e] (rev 51)
As you see my graphics cards are in separate IOMMU groups.