[libvirt] [PATCH 0/6] hostdev: handle usb detach/attach on node

[Nikolay Shirokovskiy]

Hi, all.

This patch series aims to handle case when hostdev usb is detached and then
attached back on node. Currently libvirtd does not track these events so that in
the result hostdev usb is not usable.

On the first glace it make sense to delete device from qemu when hostdev is
detached on node and then add device back when hostdev is attached back. But
these series adds a different behaviour. On detaching device is deleted from
qemu and dummy (missing hostaddr and hostbus values) hostdev is inserted, then
on attaching device on node dummy device is deleted and proper one is inserted.
This way we have the same semantics of 'missing' flag for hostdev as in case of
hostdev missing on startup/migration to different host. Also with such
approach we additionally handle cases when hostdev is missing on startup but
later is attached to node.

Known issues:

The last patch tries to handle case when hostdev attached/detached when
libvirtd is down but if fails in one scenario. If hostdev is detached and thus
dummy device in inserted in qemu then if libvirtd is down and hostdev is
attached to node then qemu tries to bind appeared hostdev to the dummy device
but fails as device is missing in qemu's mount namespace. Later when libvirtd
is up and tries to replace dummy device with actual one the device_add fails
because libusb the qemu uses tracks that deviced was missed ealier. For this
reason I proposed to get rid of dummy device in RFC [1]. Alternatively libusb
can be fixed.

[1] https://www.redhat.com/archives/libvir-list/2019-August/msg01396.html

Nikolay Shirokovskiy (6):
  qemu: track hostdev delete cause
  qemu: handle usb hostdev add/del udev events
  qemu: handle usb hostdev add/del on device DELETED_EVENT
  conf: parse hostdev missing flag
  qemu: handle libvirtd restarts during hostdev reattaching
  qemu: handle hostdev add/del when libvirtd is down

 src/conf/domain_conf.c   |  32 ++++
 src/conf/domain_conf.h   |  10 ++
 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   | 376 +++++++++++++++++++++++++++++++++++++--
 src/qemu/qemu_hotplug.c  |  94 ++++++++--
 src/qemu/qemu_hotplug.h  |   7 +-
 src/qemu/qemu_process.c  |  55 +++++-
 src/util/virhostdev.c    |   6 +-
 tests/qemuhotplugtest.c  |   2 +-
 12 files changed, 558 insertions(+), 33 deletions(-)

-- 
2.23.0