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

[Zir Blazer <zir_blazer@xxxxxxxxxxx>]

Fix: Added xen-users as CC.

________________________________
> From: nospam@xxxxxxxx 
> To: xen-users@xxxxxxxxxxxxx 
> Date: Sat, 19 Mar 2016 07:30:40 +0000 
> Subject: [Xen-users] Enabling AMD-Vi IOMMU panics Xen 
> 
> 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). 
> 
> 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). 

My answer will not really be very useful, but at least it may save you some 
time...

If there are issues with the ACPI IVRS Table, the issues are Firmware side. I 
suppose that you could try contacting Coreboot developers and asking them if 
they can give you a hand fixing it for a AMD Jaguar platform.

I don't specifically recall if Xen could, but the Linux Kernel itself could 
workaround a broken ACPI IVRS Table since you had a Boot Loader parameter that 
you could set to override the broken values of it with your own provided 
values, check here:

https://bbs.archlinux.org/viewtopic.php?id=163102

Basically, for the Linux Kernel, you could use something like iommu=1 
ivrs_ioapic[6]=00:14.0 as boot parameter or so and get a working IOMMU with a 
broken BIOS ACPI IVRS Table. However, this only works if you were going to use 
the IOMMU for QEMU-KVM-VFIO Passthrough, not Xen, but I think it could also do 
something similar to that. The problem is that I don't know what the Xen 
parameters are (If they exist), or how you are supposed to get the correct 
values to get it working.
If it is not possible to do something like that in Xen, your only choice is fix 
it Firmware-side.                                         
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