This whole pass through thingie is confusing AF so please bear with my noob-ness.

 

So everyone says if a device is in the same IOMMU group with another device then it's highly unlikely (impossible) to pass it through to a VM. In which case, we need to switch on ACS Override to break things into their own groups. Make perfect sense to me.

 

However, I noticed jbartlett had success with the below IOMMU group (without ACS)

IOMMU group 11:	[1022:1452] 40:03.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) PCIe Dummy Host Bridge
	[1022:1453] 40:03.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) PCIe GPP Bridge
	[10de:13c0] 42:00.0 VGA compatible controller: NVIDIA Corporation GM204 [GeForce GTX 980] (rev a1)
	[10de:0fbb] 42:00.1 Audio device: NVIDIA Corporation GM204 High Definition Audio Controller (rev a1)

Shouldn't that theoretically NOT work? Or are these "Dummy" and "GPP" Bridge devices hyst red herring?

 

For reference, with ACS Override, tjb_altf4 has the following IOMMU which works.

IOMMU group 21:	[1022:1452] 40:03.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) PCIe Dummy Host Bridge
IOMMU group 22:	[1022:1453] 40:03.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) PCIe GPP Bridge
IOMMU group 29:	[10de:1c03] 42:00.0 VGA compatible controller: NVIDIA Corporation GP106 [GeForce GTX 1060 6GB] (rev a1)
[10de:10f1] 42:00.1 Audio device: NVIDIA Corporation GP106 High Definition Audio Controller (rev a1)

 

My head is about to explode.

?

 

Edited August 18, 20187 yr by testdasi

step one:

 

 

#mindblown ?

 

So in short:

1. Ignore bridge devices (e.g. the dummy) - should not affect pass-through
2. Use vfio method
3. Use ACS Override
4. Use ACS Override + multifunction