While testing various iGPU pass-throughs for the Ryzen9 9950X, I've found that the PCI-E link speed is not the same as the GPU speed.
The amdgpu reset bug did not occur when I slowed down the Linux amdgpu driver to 5GT/s (Gen2), so I set the kernel parameter pcie_gen_cap. The kernel parameter does not work for the iGPU either.
The RX580 is enabled if you set it on the grub side, but not on the modprobe.d side.
If you force it to Gen2 with setpci, the iGPU reset bug (host freezes when VM is restarted) does not occur, but the iGPU becomes code 43.
The RX580 link speed drops with each kernel version (amdgpu driver version?) upgrade.
ubuntu18.04(kenrl4.15): 8GT/s -> Forced change with kernel parameters
ubuntu20.04(kernel5.4): 5GT/s
ubuntu22.04(kernel5.15): ???
ubuntu24.04(kernel6.8or6.14): 2.5GT/s
proxmox8.4(kernel6.8or6.14): 2.5GT/s
Motherboard: MSI X670E Gaming plus WiFi
CPU: Ryzen9 9950X
When booting Linux (after loading amdgpu and nouveau drivers)
iGPU: 16GT/s
AMD RX580: 2.5GT/s
NVIDIA GT750ti: 2.5GT/s
NVIDIA RTX4060ti: Unconfirmed
Immediately after Windows starts after pass-through
iGPU: 16GT/s
AMD RX580: 2.5GT/s
NVIDIA GT750ti: 2.5GT/s
NVIDIA RTX4060ti: Unconfirmed
After Windows driver installation after pass-through (in the past, I think the original speed was changed before the driver was loaded)
iGPU: 16GT/s
AMD RX580: 2.5GT/s
NVIDIA GT750ti: 8GT/s
NVIDIA RTX4060ti: Unconfirmed
The amdgpu reset bug did not occur when I slowed down the Linux amdgpu driver to 5GT/s (Gen2), so I set the kernel parameter pcie_gen_cap. The kernel parameter does not work for the iGPU either.
The RX580 is enabled if you set it on the grub side, but not on the modprobe.d side.
If you force it to Gen2 with setpci, the iGPU reset bug (host freezes when VM is restarted) does not occur, but the iGPU becomes code 43.
The RX580 link speed drops with each kernel version (amdgpu driver version?) upgrade.
ubuntu18.04(kenrl4.15): 8GT/s -> Forced change with kernel parameters
ubuntu20.04(kernel5.4): 5GT/s
ubuntu22.04(kernel5.15): ???
ubuntu24.04(kernel6.8or6.14): 2.5GT/s
proxmox8.4(kernel6.8or6.14): 2.5GT/s
Motherboard: MSI X670E Gaming plus WiFi
CPU: Ryzen9 9950X
When booting Linux (after loading amdgpu and nouveau drivers)
iGPU: 16GT/s
AMD RX580: 2.5GT/s
NVIDIA GT750ti: 2.5GT/s
NVIDIA RTX4060ti: Unconfirmed
Immediately after Windows starts after pass-through
iGPU: 16GT/s
AMD RX580: 2.5GT/s
NVIDIA GT750ti: 2.5GT/s
NVIDIA RTX4060ti: Unconfirmed
After Windows driver installation after pass-through (in the past, I think the original speed was changed before the driver was loaded)
iGPU: 16GT/s
AMD RX580: 2.5GT/s
NVIDIA GT750ti: 8GT/s
NVIDIA RTX4060ti: Unconfirmed