[pve-devel] [PATCH qemu-server] qmp helpers: device add: use HMP interface

[Fiona Ebner]

Fixes device hotplug in combination with QEMU 9.2.

QEMU commit be93fd5372 ("qdev-monitor: avoid QemuOpts in QMP device_add")
notes:

> This patch changes the behavior of QMP device_add but not HMP
> device_add. QMP clients that sent incorrectly typed device_add QMP
> commands no longer work. This is a breaking change but clients should be
> using the correct types already.

The qemu_deviceadd() helper does not have the required type
information right now, so switch to using HMP, which still behaves the
same when passing a device commandline string. QEMU commit be93fd5372
fixes passing in complex properties via JSON, but the qemu_deviceadd()
helper never uses any such, as it already only received a string (and
naively split it up).

Use HMP for 'device_del' too, simply to keep the qemu_deviceadd() and
qemu_devicedel() helpers consistent.

Switching back to QMP using the correct types in the JSON can still be
done later. Unfortunately, 'qmp-query-schema' does not provide
device-specific types, so another way is needed.

The timeout of 60 seconds is used, because that is the same that's
currently used by the 'drive_add' HMP commands and a too low timeout
is known to cause issues [0]. While 'drive_del' uses 10 minutes, there
were no issues reported with the 'device_del' operations using the
default timeout until now, but it still makes sense to increase,
because for some devices IO might need to happen during detach, so use
60 seconds for now too.

While this fixes the singular issue reported in [0] by accident,
increasing the QMP timeout like in the patches proposed there will be
needed when switching back to QMP and also covers object_{add,del}.

[0]: https://bugzilla.proxmox.com/show_bug.cgi?id=5985

Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---
 PVE/QemuServer/QMPHelpers.pm | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/PVE/QemuServer/QMPHelpers.pm b/PVE/QemuServer/QMPHelpers.pm
index 1bc9e5dc..332442f3 100644
--- a/PVE/QemuServer/QMPHelpers.pm
+++ b/PVE/QemuServer/QMPHelpers.pm
@@ -25,15 +25,14 @@ sub qemu_deviceadd {
     my ($vmid, $devicefull) = @_;
 
     $devicefull = "driver=".$devicefull;
-    my %options =  split(/[=,]/, $devicefull);
 
-    mon_cmd($vmid, "device_add" , %options);
+    PVE::QemuServer::Monitor::hmp_cmd($vmid, "device_add $devicefull", 60);
 }
 
 sub qemu_devicedel {
     my ($vmid, $deviceid) = @_;
 
-    my $ret = mon_cmd($vmid, "device_del", id => $deviceid);
+    PVE::QemuServer::Monitor::hmp_cmd($vmid, "device_del $deviceid", 60);
 }
 
 sub qemu_objectadd {
-- 
2.39.5