Re: pci passthrough with KVM

[Sebastian Hetze <s.hetze@linux-ag.com>]

On Tue, Sep 28, 2010 at 10:27:18AM +0200, Inigo Losada wrote:
> We are using pci passthrough with an SCSI Adapter card. The system is:
> 
> -  O.S:  Ubuntu 10.04.1 LTS
> -  KVM Packages: 
> 
> kvm    1:84+dfsg-0ubuntu16+0.12.3+noroms+0ubuntu9.2
> kvm-pxe   5.4.4-1ubuntu1
> qemu-kvm     0.12.3+noroms-0ubuntu9.2 
> libvirt-bin      0.7.5-5ubuntu27.2
> python-libvirt    0.7.5-5ubuntu27.2
> libvirt0        0.7.5-5ubuntu27.2
> 
> - Kernel  2.6.32.15+drm33.5.iommu    recompiled with following options :
> 
> CONFIG_DMAR=y
> CONFIG_INTR_REMAP=y
> 
> - Apparmor is stopped
> 
> When we started the virtual machine we obtain the following error: 
> 
> char device redirected to /dev/pts/3 
> device: 04:04.0: driver="pci-assign" host="04:04.0" 
> Failed to assign irq for "04:04.0": Operation not permitted 
> Perhaps you are assigning a device that shares an IRQ with another device? 

So do you?

The notes in
http://www.linux-kvm.org/page/How_to_assign_devices_with_VT-d_in_KVM
give you this information:

    *  VT-d spec specifies that all conventional PCI devices behind a
    *  PCIe-to PCI/PCI-X bridge or conventional PCI bridge can only be
    *  collectively assigned to the same guest. PCIe devices do not have
    *  this restriction.
    *  If the device doesn't support MSI, and it shares IRQ with other
    *  devices, then it cannot be assigned due to host irq sharing for
    *  assigned devices is not supported. You will get warning message
    *  when you assign it. Notice this also apply to the devices which
    *  only support MSI-X. 

What do you find in /proc/interrupts ?

Best regards,

  Sebastian