On Tue, Jun 7, 2011 at 4:04 AM, Chris Wright <chrisw@xxxxxxxxxxxx> wrote: > * 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? > I had tried without passthrough on RHEL 6.1 GA kernel. Was seeing hangs and panics. Will check if non passthrough mode works on latest kernel. > 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. > For testing I had made a hack in 2.6.39 kernel which will prevent demoting to 32bit DMA mask and thereby prevent calling of domain_remove_one_dev_info() for the specific VF device I was using and it had worked. So as you said I may not hit the issue in latest kernel. Will try that. > thanks, > -chris > Thanks for the response and suggestions. Padmanabh -- 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
