Hi! 07.01.2020, 23:08, "Michael S. Tsirkin" <m...@redhat.com>: > On Fri, Jan 03, 2020 at 11:44:27AM +0000, Dr. David Alan Gilbert wrote: >> > 1) Guest: writes to slot's pci config >> > 2) QEMU: pcie_cap_slot_write_config -> pcie_unplug_device >> > >> > So, it's only guest driven action and qdev_unplug doesn't help here. >> >> Hmm we need to find a way to stop that; lets see if Michael Tsirkin has >> any ideas (cc'd) - I'm thinking if we could defer the unplug until the >> end of the migration we'd be OK; but it feels racy as to whether the >> destination is started with the device that the guest is unplugging. >> >> Dave > > It's true - and same is possible with PCI, guest can remove device > at will. > > Also, while libvirt learned not to start device del while migration > is active, it's annoying to have to wait for device del > to complete before migration can be started. > > I guess we can make device invisible to guest - that concept > now exists because of failover, and can maybe be reused here. > > Alternatively or additionally - for a while now I wanted to only remove > the device if guest powered it out and removal was requested. Again it > might be easier now that we have a concept of an invisible device. >
I sent an rfc patch that implements deferred device unplug: pcie: Defer hot unplug until migration is complete Please take a look at it. Regards, Yury
