[+cc Alex, kvm, linux-pci] On Fri, Aug 13, 2021 at 09:43:39AM +0200, Idar Lund wrote: > Hi, > > I've been struggling with an error in linux since 5.11. Please find my bug > report here: > https://bugzilla.redhat.com/show_bug.cgi?id=1945565 > > Then I stumbled upon this mail thread: > https://www.spinics.net/lists/linux-pci/msg102243.html which seems related. > > Is there another way to do this in 5.11+ or is this an unintentionally bug > that got introduced in 5.11? Hi Idar, sorry for the trouble and thanks for the report! I cc'd some VFIO experts who know more than I do about this. If I understand correctly, you have a PCI XHCI controller: pci 0000:06:00.0: [1b73:1100] type 00 class 0x0c0330 xhci_hcd 0000:06:00.0: xHCI Host Controller and you want to unbind the xhci_hcd driver and bind vfio-pci instead: # echo '0000:06:00.0' > /sys/bus/pci/devices/0000\:06\:00.0/driver/unbind # echo 0x1b73 0x1100 > /sys/bus/pci/drivers/vfio-pci/new_id In v5.10 (5.10.17-200.fc33.x86_64) this worked fine, but in v5.11 (5.11.9-200.fc33.x86_64) the "new_id" write returns -EEXIST and binding to vfio-pci fails. The patch you pointed out appeared in v5.11 as 3853f9123c18 ("PCI: Avoid duplicate IDs in driver dynamic IDs list") [1], and I agree it looks suspicious. There haven't been any significant changes to pci-driver.c since then. Have you added "0x1b73 0x1100" to vfio-pci/new_id previously? I think in v5.10, that would silently work (possibly adding duplicate entries to the dynamic ID list) and every write to vfio-pci/new_id would make vfio-pci try to bind to the device. In v5.11, if you write a duplicate ID to vfio-pci/new_id, you would get -EEXIST and no attempt to bind. As far as I know, the dynamic ID list is not visible in sysfs, so it might be hard to avoid writing a duplicate. But if the vfio-pci dynamic ID list already contains "0x1b73 0x1100", you should be able to ask vfio-pci to bind to the device like this: # echo 0000:06:00.0 > /sys/bus/pci/drivers/virtio-pci/bind I don't know if that's a solution, but would be useful to know whether it's a workaround. [1] https://git.kernel.org/linus/3853f9123c18
