Hi,
I'm trying to setup a MythTV backend with Mythbuntu in a VM. I'm running Fedora 12 as host. I have 2 DVB-C cards in my system. The system contains an AM2 cpu which supports AMD's virtualization technology (which is switched on in bios). I've enabled SELinux to:
- Allow virt to manage devince configuration, (pci)
- Allow virt to use usb devices

The error which I get is:
Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/engine.py", line 588, in run_domain
vm.startup()
File "/usr/share/virt-manager/virtManager/domain.py", line 150, in startup
self._backend.create()
File "/usr/lib64/python2.6/site-packages/libvirt.py", line 293, in create
if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: internal error unable to start guest: char device redirected to /dev/pts/1
Failed to assign irq for "01:06.0": Operation not permitted
Perhaps you are assigning a device that shares an IRQ with another device?
Failed to initialize assigned device host=01:06.0

My /proc/interrupts contains this list:

CPU0 CPU1
0: 129 12 IO-APIC-edge timer
1: 0 2 IO-APIC-edge i8042
7: 1 0 IO-APIC-edge
8: 0 1 IO-APIC-edge rtc0
9: 0 0 IO-APIC-fasteoi acpi
12: 1 4 IO-APIC-edge i8042
14: 41 24670 IO-APIC-edge pata_amd
15: 0 0 IO-APIC-edge pata_amd
16: 244 160 IO-APIC-fasteoi saa7146 (0)
17: 0 348 IO-APIC-fasteoi saa7146 (1)
18: 7 26 IO-APIC-fasteoi firewire_ohci
20: 5 19394 IO-APIC-fasteoi sata_nv
21: 376 495 IO-APIC-fasteoi nouveau, HDA Intel
22: 1171 24778 IO-APIC-fasteoi ohci_hcd:usb2
23: 12 539 IO-APIC-fasteoi ehci_hcd:usb1, sata_nv
24: 19324 212 PCI-MSI-edge eth0
NMI: 0 0 Non-maskable interrupts
LOC: 403323 452940 Local timer interrupts
SPU: 0 0 Spurious interrupts
CNT: 0 0 Performance counter interrupts
PND: 0 0 Performance pending work
RES: 44192 24782 Rescheduling interrupts

Which I think means that no IRQs are shared. Devices 16 & 17 are the one I want to Passthrough. Can someone point me in the right direction on how to solve this problem?

I'll answer my own question as no one else did and it might benefit someone.

KVM needs hardware support to function (otherwise you're using Qemu emulation and that's slow and not really KVM). There are however gradations in this hardware support:
- The 1st gradation is virtualization support in the cpu. AMD support this kind of virtualization since the Athlon on AM2 generation, Intel supports it in the Core cpu's though cheaper Core cpu's might lack this support. Check Intel website to see if your Intel cpu supports it or not
- The 2nd gradation is support in the northbridge. As far as I know, so far only intel chipsets for the Core i9, i7 and i5 have this "IOMMU" support. AMD's new 8x0 chipsets with mainboards containing them due to be released this month are also suspected of containing this IOMMU support.

In short KVM needs the first gradation to function at all. KVM needs the 2nd gradation for functionality like PCI Passthrough. My cpu only has AMD-V, so PCI passthrough won't work for me. If I want PCI passthrough in a VM I'd have to use Xen.

1 members found this post helpful.

Yes, and with Intel you need VT-d.

Thanks for that clarification. I'm also running a MythTV backend in a virtual machine on an AMD-V machine. I'm working in a Debian/Ubuntu based environment so I was interested in migrating to KVM since Ubuntu has stopped supporting Xen and it's unclear to me what Debian has planned for Xen in the future. I'd tried setting up KVM and got the exact same error messages that you did. I've been banging my head against a wall, and while I wish there was a solution it's at least good to have the knowledge that it's a hardware problem so I can just work with what I've got.

Is your AMD-V enabled? It might show all the right flags in /proc/cpuinfo, but be disabled in the BIOS.

@dyasny It's not relevant to skug67's problem. He wants to use PCI passthrough. AMD-V alone is not enough for that and there are no AMD systems available yet that will support PCI passthrough on KVM. He'll have to revert to Xen or use the host for MythTV. The latter is what I did.