From b44caea0b205fa79054e576f5abb4545c1557488 Mon Sep 17 00:00:00 2001
From: Tim Wiederhake <twiederh@redhat.com>
Date: Wed, 6 Jan 2021 12:12:40 +0100
Subject: [PATCH] qemuDomainChangeNet: Check changed virtio network driver
 options
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Changes to a virtio network device such as
  <interface type="network">
    <model type="virtio"/>
    <driver iommu="on" ats="on"/> <!-- this line added -->
    ...
  </interface>
were quietly dismissed by `virsh update-device ... --live`.

Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 src/qemu/qemu_hotplug.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index ec5c522000..f336a90c8e 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -3600,6 +3600,16 @@ qemuDomainChangeNet(virQEMUDriverPtr driver,
         goto cleanup;
     }
 
+    if (!!olddev->virtio != !!newdev->virtio ||
+        (olddev->virtio && newdev->virtio &&
+         (olddev->virtio->iommu != newdev->virtio->iommu ||
+          olddev->virtio->ats != newdev->virtio->ats ||
+          olddev->virtio->packed != newdev->virtio->packed))) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                       _("cannot modify virtio network device driver options"));
+           goto cleanup;
+   }
+
     /* data: this union will be examined later, after allocating new actualdev */
     /* virtPortProfile: will be examined later, after allocating new actualdev */