pc: Factor out (un)plug handling of virtio-md-pci devices

Let's factor out (un)plug handling, to be reused from arm/virt code.

Provide stubs for the case that CONFIG_VIRTIO_MD is not selected because
neither virtio-mem nor virtio-pmem is enabled. While this cannot
currently happen for x86, it will be possible for arm/virt.

Message-ID: <20230711153445.514112-3-david@redhat.com>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/hw/virtio/virtio-md-pci.c b/hw/virtio/virtio-md-pci.c
index 6b02ff908e..e849c3131d 100644
--- a/hw/virtio/virtio-md-pci.c
+++ b/hw/virtio/virtio-md-pci.c
@@ -13,6 +13,69 @@
 #include "qemu/osdep.h"
 #include "hw/virtio/virtio-md-pci.h"
 #include "hw/mem/memory-device.h"
+#include "qapi/error.h"
+
+void virtio_md_pci_pre_plug(VirtIOMDPCI *vmd, MachineState *ms, Error **errp)
+{
+    DeviceState *dev = DEVICE(vmd);
+    HotplugHandler *bus_handler = qdev_get_bus_hotplug_handler(dev);
+    MemoryDeviceState *md = MEMORY_DEVICE(vmd);
+    Error *local_err = NULL;
+
+    if (!bus_handler && dev->hotplugged) {
+        /*
+         * Without a bus hotplug handler, we cannot control the plug/unplug
+         * order. We should never reach this point when hotplugging on x86,
+         * however, better add a safety net.
+         */
+        error_setg(errp, "hotplug of virtio based memory devices not supported"
+                   " on this bus.");
+        return;
+    }
+    /*
+     * First, see if we can plug this memory device at all. If that
+     * succeeds, branch of to the actual hotplug handler.
+     */
+    memory_device_pre_plug(md, ms, NULL, &local_err);
+    if (!local_err && bus_handler) {
+        hotplug_handler_pre_plug(bus_handler, dev, &local_err);
+    }
+    error_propagate(errp, local_err);
+}
+
+void virtio_md_pci_plug(VirtIOMDPCI *vmd, MachineState *ms, Error **errp)
+{
+    DeviceState *dev = DEVICE(vmd);
+    HotplugHandler *bus_handler = qdev_get_bus_hotplug_handler(dev);
+    MemoryDeviceState *md = MEMORY_DEVICE(vmd);
+    Error *local_err = NULL;
+
+    /*
+     * Plug the memory device first and then branch off to the actual
+     * hotplug handler. If that one fails, we can easily undo the memory
+     * device bits.
+     */
+    memory_device_plug(md, ms);
+    if (bus_handler) {
+        hotplug_handler_plug(bus_handler, dev, &local_err);
+        if (local_err) {
+            memory_device_unplug(md, ms);
+        }
+    }
+    error_propagate(errp, local_err);
+}
+
+void virtio_md_pci_unplug_request(VirtIOMDPCI *vmd, MachineState *ms,
+                                  Error **errp)
+{
+    /* We don't support hot unplug of virtio based memory devices */
+    error_setg(errp, "virtio based memory devices cannot be unplugged.");
+}
+
+void virtio_md_pci_unplug(VirtIOMDPCI *vmd, MachineState *ms, Error **errp)
+{
+    /* We don't support hot unplug of virtio based memory devices */
+}
 
 static const TypeInfo virtio_md_pci_info = {
     .name = TYPE_VIRTIO_MD_PCI,