* Stefan Weil (s...@weilnetz.de) wrote: > On 10/14/16 10:25, Dr. David Alan Gilbert wrote: > > * Stefan Weil (s...@weilnetz.de) wrote: > > > Instead of allocating a VMStateDescription for each NIC instance, > > > the code now uses a single constant VMStateDescription for all > > > instances. That implies that the name field is always the same. > > > > Doesn't this break migration compatibility? > > > > You might be able to get around that (in the forward direction only) > > by adding an entry to qdev_alias_table but I'm not sure. > > > > Dave > > I'm not an expert for migration (never used it myself). > > Is migration compatibility a must, even for non default settings > like the NICs implemented by eepro100.c? I assume that applications > which use migration will usually run with an e1000 NIC. > > Or can we break migration compatibility and add that information > to the release notes?
We normally keep migration compatibility for all devices in the forward direction unless it's something really obscure; I don't think an e100 is. > How does e1000 handle migration if QEMU was started with a > e1000-82544gc NIC and migrated to a e1000-82545em NIC? That's not required to work; you're required to have the same device configuration on the destination as the source. $ qemu-system-x86_64 -nographic -device e1000-82544gc (qemu) migrate "exec:cat > t.mig" $ qemu-system-x86_64 -nographic -device e1000-82545em -incoming "exec:cat t.mig" qemu-system-x86_64: get_pci_config_device: Bad config data: i=0x2 read: c device: f cmask: ff wmask: 0 w1cmask:0 qemu-system-x86_64: error while loading state for instance 0x0 of device '0000:00:04.0/e1000' qemu-system-x86_64: load of migration failed: Invalid argument Now, note that what's happening here is that e1000 is doing a similar trick to what you're doing - i.e. all devices end up getting migrated as 'e1000' in the device string (0000:00:04.0/e1000). The scheme you end up with is OK, but the problem is it's just different from what we have now, so existing streams with device names like '0000:00:04.0/i82550' won't load. Dave > > Stefan > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
