[Xen-users] Enabling AMD-Vi IOMMU panics Xen

[小太 <nospam@xxxxxxxx>]

Hello

I've been trying to enable IOMMU on a apu2b4 board (http://www.pcengines.ch/apu2b4.htm) so I can pass network interfaces into a HVM domU (pfsense FreeBSD).

Note that the board "by default" doesn't support IOMMU, but since it runs coreboot, I compiled in some code that initialises the IOMMU (so if this bug seems to be caused by the BIOS, hopefully it can be fixed fairly quickly).

I'm booting Xen 4.6.0 with Ubuntu 16.04 as dom0, with the following "base" command line:
loglvl=all guest_loglvl=all com1=115200,8n1 console=com1 iommu=debug

Using that command line, the IOMMU does not get enabled due to some problems with the IVRS table (which seems to be generated by AMD's closed-source AGESA), which you can see in "apic_verbosity=debug.log" (attached).

However, the system boots fine and my VM can be started without any problems.

If I add the iommu=no-amd-iommu-perdev-intremap option, I get the "iommu=no-amd-iommu-perdev-intremap apic_verbosity=debug.log" output. Xen panics without even getting to booting the dom0.

If I add the iommu=no-intremap.log option, Xen and the dom0 boots fine, but then panics when trying to start a domU. The attached "iommu=no-intremap.log" shows Xen reassigning a PCI device while booting the domU, but the panic happens regardless of whether PCI passthrough is specified in the domU config or not.

I've also attached the domU config file (pfsense.conf) and a lspci of the IOMMU device with its configuration registers (iommu-pci-device.log).

I can also recompile Xen or coreboot if needed to help fix the problem.

Attachment: apic_verbosity=debug.log
Description: Text Data

Attachment: iommu=no-amd-iommu-perdev-intremap apic_verbosity=debug.log
Description: Text Data

Attachment: iommu=no-intremap.log
Description: Text Data

Attachment: iommu-pci-device.log
Description: Text Data

Attachment: pfsense.conf
Description: config/conf

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