[pve-devel] [PATCH qemu-server v2] disable usb hotplug for now

[Dominik Csapak]

we have a few problems with hotplug at the moment:
qemu may add usb hubs when adding usb devices but fails to remove them
when removing the usb device (this is a qemu bug)

also when starting a guest with a usb device we add ehci and uchi
controllers, which we cannot hot unplug

with those devices, it is impossible to live migrate the guest
to another host, meaning even if you remove all usb devices,
the migrate fails

so we deactivate usb hotplugging for now

Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
---
changes from v1:
 * used an coherent way of disabling the usb hotplug codepaths
 PVE/QemuServer.pm | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index b6ad27a..da26efe 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -3273,6 +3273,10 @@ sub vm_deviceplug {
 
     } elsif ($deviceid =~ m/^usb(\d+)$/) {
 
+	die "usb hotplug currently not reliable\n";
+	# since we can't reliably hot unplug all added usb devices
+	# and usb passthrough disables live migration
+	# we disable usb hotplugging for now 
 	qemu_deviceadd($vmid, PVE::QemuServer::USB::print_usbdevice_full($conf, $deviceid, $device));
 
     } elsif ($deviceid =~ m/^(virtio)(\d+)$/) {
@@ -3372,6 +3376,10 @@ sub vm_deviceunplug {
 
     } elsif ($deviceid =~ m/^usb\d+$/) {
 
+	die "usb hotplug currently not reliable\n";
+	# when unplugging usb devices this way, 
+	# there may be remaining usb controllers/hubs
+	# so we disable it for now
 	qemu_devicedel($vmid, $deviceid);
 	qemu_devicedelverify($vmid, $deviceid);
 
@@ -3910,6 +3918,9 @@ sub vmconfig_hotplug_pending {
 		    vm_deviceunplug($vmid, $conf, $opt);
 		}
 	    } elsif ($opt =~ m/^usb\d+/) {
+		die "skip\n";
+		# since we cannot reliably hot unplug usb devices
+		# we are disabling it
 		die "skip\n" if !$hotplug_features->{usb} || $conf->{$opt} =~ m/spice/i;
 		vm_deviceunplug($vmid, $conf, $opt);
 	    } elsif ($opt eq 'vcpus') {
@@ -3963,6 +3974,9 @@ sub vmconfig_hotplug_pending {
 		    vm_deviceunplug($vmid, $conf, $opt);
 		}
 	    } elsif ($opt =~ m/^usb\d+$/) {
+		die "skip\n";
+		# since we cannot reliably hot unplug usb devices
+		# we are disabling it
 		die "skip\n" if !$hotplug_features->{usb} || $value =~ m/spice/i;
 		my $d = eval { PVE::JSONSchema::parse_property_string($usbdesc->{format}, $value) };
 		die "skip\n" if !$d;
-- 
2.1.4