kernel support for separate IOMMU groups or ACS

[ng0177]

The grub based kernel patch

pcie_acs_override=downstream

as documented has been implemented successfully.

All possible BIOS settings such as

• AMD IOMMU
• SR-IOV

are activated on a MSI B450 Gaming Plus Max AMD.

However, the groups are still not separated. The goal is to passthrough ASM1042 to avoid mouse lag. Any ideas?

pvesh get /nodes/pve/hardware/pci --pci-class-blacklist ""

 

[leesteken]

Using a X570(S) motherboard will give you much better groups (as all other AM4 chipsets have limited groups). Is there no other USB controller (coming from the CPU) that is in an isolated group? Maybe buy a USB add-in PCIe card (that is known to work with passthrough) and put it in the PCIe x16 slot (coming from the CPU)?
You could try pcie_acs_override=downstream,multifunction (check with cat /proc/cmdline whether it is active) but that allows the VM to read all of the system memory and is therefore not secure.

 

[ng0177]

Maybe buy a USB add-in PCIe card (that is known to work with passthrough) and put it in the PCIe x16 slot (coming from the CPU)?

I forgot to mention that the ASMedia ASM1042 Superspeed is such a card was bought for that purpose. However, it is in a PCIe x1 slot as it fits in it - the x16 looks to wide to me (and has the obligatory graphics card in it anyway); but there is a x4 slot free which again looks too wide.

I just tried pcie_acs_override=downstream,multifunction which is active and [B]multifunction[/B] separates the groups albeit a security risk. Thank you.

 

[leesteken]

I forgot to mention that the ASMedia ASM1042 Superspeed is such a card was bought for that purpose. However, it is in a PCIe x1 slot as it fits in it - the x16 looks to wide to me (and has the obligatory graphics card in it anyway); but there is a x4 slot free which again looks too wide.

PCIe is fully compatible in larger and smaller slots (as long as the end of the slot is open, with reduced bandwidth).
Unfortunately, your B450 motherboard only support passthrough on the PCIe x16 slot.

I just tried pcie_acs_override=downstream,multifunction which is active and [B]multifunction[/B] separates the groups albeit a security risk. Thank you.

I would advise against it. But as long as you are aware of the security issue that comes with it, it's your choice of course.

 

[ng0177]

I would advise against it.

Thanks. I am just testing now to see how it works. I will be more cautious and get a license later.

 

[LnxBil]

I will be more cautious and get a license later.

license for what?

 

[ng0177]

license for what?

https://www.proxmox.com/en/proxmox-virtual-environment/pricing

 

[leesteken]

https://www.proxmox.com/en/proxmox-virtual-environment/pricing

That is not a license (which is AGPL3 for open-source Proxmox) but a support subscription. These are legally very different things, which people often mix up. You don't need a license to use Proxmox or any of its features. You buy a subscription to sponsor Proxmox and/or to get support tickets.

 

[ng0177]

Understood. If I (should) get everything up and running, I feel I have a moral obligation to sponsor them. BTW, I still do not know, if I have a conceptual problem.