* Alex Williamson (alex.williamson@xxxxxxxxxx) wrote: > On Mon, 2011-06-06 at 14:39 +0530, padmanabh ratnakar wrote: > > Hi, > > I am using linux kernel 2.6.39. I have a IBM x3650 M3 system. > > I have used following boot options - > > intel_iommu=on iommu=pt > > > > I was loading/unloading my NIC driver(be2net) with num_vfs=7. > > > > After some iterations I get following DMAR errors - > > Jun 4 03:50:20 rhel6 kernel: Uhhuh. NMI received for unknown reason > > 2d on CPU 0. > > Jun 4 03:50:20 rhel6 kernel: Do you have a strange power saving mode enabled? > > Jun 4 03:50:20 rhel6 kernel: Dazed and confused, but trying to continue > > Jun 4 03:50:20 rhel6 kernel: DRHD: handling fault status reg 2 > > Jun 4 03:50:20 rhel6 kernel: DMAR:[DMA Read] Request device [1a:00.2] > > fault addr 78077000 > > Jun 4 03:50:20 rhel6 kernel: DMAR:[fault reason 02] Present bit in > > context entry is clear > > > > I was trying to debug this. I dont understand iommu code much. > > The physical address belongs the printed PCI function and there should > > not have been an error. > > > > I am unable to see pci_dev(pdev) of VFs getting removed from > > si_domain->devices list(intel-iommu.c) > > when driver gets unloaded calling pci_disable_sriov() freeing VF pdevs. > > Looks like issue happens when when freed pdev is allocated again and > > as it is already in list, > > required initializations dont happen. > > > > I dont know if my understanding is correct. Can anyone point me to > > what the issue may be? Yes, that's correct. The (now replaced) check identity_mapping() will succeed when the pci_dev is recycled (it's freed, but never removed from the list, this is an issue with passtrhough mode and device creation/desctruction). This false match happens w/ a brand new pci_dev which still has default 32bit DMA mask, so it is removed from pt domain. During removal domain_remove_one_dev_info() test that matches only on bus/devfn (now also segment) will match despite the fact that the info->pdev != pdev->dev.archdata.iommu. Then...Oops > Typically devices are removed from the domain via > drivers/pci/intel-iommu.c:device_notifier(), which is called as the > device is unbound from the driver. However, this seems to get skipped > when running in passthrough mode, so I'm not sure where that's supposed > to occur. Does it happen w/o passthrough? If you blacklist the driver then a create/delete may do similar (haven't tested that idea). > Also note that some > intel-iommu fixes have rolled into 3.0.0-rc2, you might want to update > and see if anything is better there. Thanks, The change in identity_mapping() means we won't demote to 32-bit DMA (drop out of pt domain), so I don't think we'll see the same issue. thanks, -chris -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
