I found this problem, too. A VM used a NIC with PCI-passthrough mode. Then I shutdown the VM, and tried to give the NIC back to the host. But I found I couldn't assign the NIC to the host again. This problem didn't occur each time. If I did this steps for ten times, I could see it at least once.
The kernel version was 2.6.32. I used Intel e1000e driver for the NIC. Here are some of the logs: kernel: e1000e 0000:02:00.1: enabling device (0000 -> 0002) kernel: e1000e 0000:02:00.1: PCI INT B -> GSI 17 (level, low) -> IRQ 17 kernel: 0000:02:00.1: 0000:02:00.1: PHY reset is blocked due to SOL/IDER session. kernel: 0000:02:00.1: 0000:02:00.1: The NVM Checksum Is Not Valid kernel: e1000e 0000:02:00.1: PCI INT B disabled -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/754591 Title: NIC doesn't work when it had been used before Status in QEMU: New Bug description: Environment: ------------ Host OS (ia32/ia32e/IA64): All Guest OS (ia32/ia32e/IA64): All Guest OS Type (Linux/Windows):All kvm.git Commit:3b840cc27e5b831a26e3303096b88e112d1cf59f qemu-kvm Commit:df85c051d780bca0ee2462cfeb8ef6d9552a19b0 Host Kernel Version:2.6.38+ Hardware:Westmere-EP / Sandy Bridge Bug detailed description: -------------------------- NIC doesn't work when it had been used before. Statically assign a NIC to guest, it works well. Then shutdown the guest, and assign the same NIC to a guest again. The NIC doesn't work. The dmesg of the guest is as following. -- Intel(R) Gigabit Ethernet Network Driver - version 2.1.0-k2 Copyright (c) 2007-2009 Intel Corporation. ACPI: PCI Interrupt Link [LNKC] enabled at IRQ 11 igb 0000:00:03.0: PCI INT A -> Link[LNKC] -> GSI 11 (level, high) -> IRQ 11 igb 0000:00:03.0: setting latency timer to 64 alloc irq_desc for 24 on node -1 alloc kstat_irqs on node -1 igb 0000:00:03.0: irq 24 for MSI/MSI-X alloc irq_desc for 25 on node -1 alloc kstat_irqs on node -1 igb 0000:00:03.0: irq 25 for MSI/MSI-X alloc irq_desc for 26 on node -1 alloc kstat_irqs on node -1 igb 0000:00:03.0: irq 26 for MSI/MSI-X igb 0000:00:03.0: PHY reset is blocked due to SOL/IDER session. igb 0000:00:03.0: The NVM Checksum Is Not Valid igb 0000:00:03.0: PCI INT A disabled igb: probe of 0000:00:03.0 failed with error -5 Reproduce steps: ---------------- 1.statically assign a NIC to a guest, check if it works well 2.shutdown the guest. 3.statically assign the same NIC to a guest (NIC doesn't work now).