+++ This bug was initially created as a clone of Bug #849223 +++ **** Description of problem: When qemu-dm unplugs an emulated NIC, as requested by the RHEL-6 guest kernel, it intends to squash the iomem region(s) belonging to the NIC being removed. However, a bug in the unregister_iomem() function may cause removal of another card's region, for example one belonging to a passthru VF. With the erroneously removed range, the VF's MSI-X registers are impossible to program for the guest. **** Version-Release number of selected component (if applicable): All versions up to xen pkg build -141. **** How reproducible: Seems to be host config dependent -- 100% reproducible on some machines, 0% reproducible on others. May depend on the emulated NIC's model (rtl8139 didn't seem to trigger the bug, e1000 did). **** Steps to Reproduce: 1. Set up ixgbevf passthru in dom0 like this: - hypervisor command line: dom0_mem=2048M iommu=1 - vmlinuz command line: pci_pt_e820_access=on - /etc/modprobe.conf: options ixgbe max_vfs=1 - blacklist the ixgbevf module - make sure the pciback module hides/seizes the one VF per each PF (=1 VF/port) - bring up the PF(s) in the host 2. Install a RHEL-6.3 guest: - make sure the xen_emul_unplug parameter is absent from the guest command line - use the e1000 model emulated NIC - pass through one VF in total to the guest - bring up the VF in the guest **** Actual results: - qemu-dm logs something like region type 0 at [f4000000,f4020000). squash iomem [f4024000, f4024030). Those ranges should match -- the first line describes the region belonging to the emulated NIC being unplugged, but the region actually squashed belongs to the VF. - the MSI-X interrupts are configured for the VF, but their counters stay 0 in /proc/interrupts, and there's no traffic. 48: 0 PCI-MSI-edge eth1-rx-0 49: 0 PCI-MSI-edge eth1-tx-0 50: 0 PCI-MSI-edge eth1:mbx **** Expected results: The VF should work. **** Additional info: - See the three comments starting at bug 849223 comment 146 for analysis and patches. - This bug may be masked by RHEL-6 guest kernel bug 849223. A working VF requires (may require, dependent on the host) fixes for both bugs.
*** This bug has been marked as a duplicate of bug 861349 ***