[pve-devel] [PATCH v2 qemu-server] qmp helpers: device add/del: 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.

A timeout of 30 seconds is used rather then relying on the low default
like before, since device plug operations require actions by the guest
kernel and might require IO. Device plug is often an interactive
operation, so a too high timeout could lead to bad UX. Should specific
devices need a higher timeout, it can still be increased further for
them in the future.

Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---

Changes in v2:
* also mention 'del' in commit title
* fix commit message (bug #5985 is not actually fixed by this, that
  requires bumping the timeout for netdev_add)
* use 30 seconds as a timeout (see commit message for rationale)

 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..9b077394 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", 30);
 }
 
 sub qemu_devicedel {
     my ($vmid, $deviceid) = @_;
 
-    my $ret = mon_cmd($vmid, "device_del", id => $deviceid);
+    PVE::QemuServer::Monitor::hmp_cmd($vmid, "device_del $deviceid", 30);
 }
 
 sub qemu_objectadd {
-- 
2.39.5