Re: [libvirt] [PATCH v2 00/11] hostdev: handle usb detach/attach on node

Hi, While reviewing these I got one question that I think it's better asked here since it's not related to a single patch. I understand the use case for udev machinery to handle the device removal event - in fact, I wonder if this should be done to all hostdevs, not just USB - but I'm not sure about the handling of device add. Let's say you have a server running lots of guests and an administrator physically disconnect a USB device that might have been in used as hostdev by any of them. It makes sense to remove the device from the domain in this scenario because, well, the device isn't there anymore. But when the admin connects the same USB device back, is he/she really expecting the device to be automatically assigned to the same guest, without direct action? Isn't there a chance of this admin reconnect back the USB device to the server for any other use, then see Libvirt automatically re-assign the device back to the guest that was using it before, and get not so pleased about it (i.e. furiously opening a new Libvirt bug)?

Thanks, DHB On 9/9/19 8:33 AM, Nikolay Shirokovskiy wrote: > *Notes* > > Deleting usb device from qemu is synchronous operation (although it > is not stated in qemu API). I did not used this knowledge in the > series. > > The last patch is remnant of previus version of the series yet it is useful. > > Diff to previous[1] version: > - don't use dummy device while host usb device is unplugged > > [1] https://www.redhat.com/archives/libvir-list/2019-August/msg01413.html > > Nikolay Shirokovskiy (11): > qemu: track hostdev delete intention > qemu: support host usb device unplug > qemu: support usb hostdev plugging back > qemu: handle host usb device add/del udev events > qemu: handle libvirtd restart after host usb device unplug > qemu: handle race on device deletion and usb host device plugging > qemu: hotplug: update device list on device deleted event > qemu: handle host usb device plug/unplug when libvirtd is down > qemu: don't mess with non mandatory hostdevs on reattaching > qemu: handle detaching of unplugged hostdev > conf: parse hostdev missing flag > > src/conf/domain_conf.c | 32 +++ > src/conf/domain_conf.h | 15 ++ > src/qemu/Makefile.inc.am | 2 + > src/qemu/qemu_conf.h | 3 + > src/qemu/qemu_domain.c | 2 + > src/qemu/qemu_domain.h | 2 + > src/qemu/qemu_driver.c | 431 ++++++++++++++++++++++++++++++++++++++- > src/qemu/qemu_hotplug.c | 104 ++++++++-- > src/qemu/qemu_hotplug.h | 3 +- > src/qemu/qemu_process.c | 59 ++++++ > src/util/virhostdev.c | 2 + > tests/qemuhotplugtest.c | 2 +- > 12 files changed, 637 insertions(+), 20 deletions(-) >