Hi Serge I agree to "created on xenial -> migrating to trusty" not being supported. I already tended to even say "created on xenial with the Trusty machine type -> migrating to trusty" is not supported as well (at least it is failing for all combos I tried.
But I wonder how far "anything moving backward" should go. Especially I found that the "created on Trusty, migrated to xenial (works), but later migrated back to trusty (fails)" seems affected by it as well. I'd have thought that this would be supported. What is you opinion on this more specific case? -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1536487 Title: Unable to migrate pc-i440fx-2.4 KVM guest from QEMU 2.5.0 to QEMU 2.4.1 Status in QEMU: Fix Released Status in qemu package in Ubuntu: Fix Released Status in qemu source package in Xenial: Triaged Bug description: When migrating a pc-i440fc-2.4 KVM guest from QEMU 2.5.0 to QEMU 2.4.1, the target QEMU errors out: qemu-system-x86_64: error while loading state for instance 0x0 of device 'fw_cfg' This appears to be related to the addition of a DMA interface to fw_cfg last October: http://lists.nongnu.org/archive/html/qemu- devel/2015-10/msg04568.html "info qtree" on the source QEMU shows that the DMA interface for fw_cfg had been enabled: bus: main-system-bus type System ... dev: fw_cfg_io, id "" iobase = 1296 (0x510) dma_iobase = 1300 (0x514) dma_enabled = true Incidentally, this guest had just undergone a migration from QEMU 2.4.1 to QEMU 2.5.0, so it looks like DMA was enabled simply through the migration. It seems to me that the DMA interface for fw_cfg should only be enabled on pc-i440fx-2.5 machines or higher. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1536487/+subscriptions
