Windows guests have trouble dealing with usb devices having identical
serial numbers. So, assign unique serial numbers to usb hid devices.
All other usb devices have this already.
In the past the fixed serial number has been used to indicate working
remote setup to linux guests. Here is a bit of history:
* First there was nothing.
* Then I added a rule to udev checking for serial == 42.
(this is in rhel-6).
* Then systemd + udev merged.
* Then I changed the rule to check for serial != 1 instead, so we can
use any serial but "1" which is the one the old broken devices had
(this is in rhel-7). March 2014 in upstream systemd.
* Then all usb power management rules where dropped from systemd (June
2015). Which I figured today (Sept 2018), after wondering that the
rules are gone in fedora 28.
So, three years ago the serial number check was dropped upstream, yet I
hav't seen a single report about autosuspend issues (or cpu usage for
usb emulation going up, which is the typical symtom).
So I figured I can stop worring that changing the serial number will
break things and just do it.
And even if it turns out autosuspend is still an issue: I think
meanwhile we can really stop worrying about guests running in old qemu
versions with broken usb suspend (fixed in 0.13 !). If needed we can
enable autosuspend unconditionally in guests.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20190110125108.22834-1-kraxel@redhat.com
b63e10508b