[Qemu-devel] [PATCH v2 2/2] virtio-pci: Disable modern interface if backend without VIRTIO_F_VERSION_1

[Maxime Coquelin <maxime.coquelin@redhat.com>]

This patch makes pci devices plugging more robust, by not confusing
guest with modern interface when the backend doesn't support
VIRTIO_F_VERSION_1.

Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Marcel Apfelbaum <marcel@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 hw/virtio/virtio-pci.c | 15 +++++++++++++++
 hw/virtio/virtio-pci.h |  5 +++++
 2 files changed, 20 insertions(+)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 755f921..9e88d7b 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1581,6 +1581,21 @@ static void virtio_pci_device_plugged(DeviceState *d, Error **errp)
     uint32_t size;
     VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
 
+    /*
+     * Virtio capabilities present without
+     * VIRTIO_F_VERSION_1 confuses guests
+     */
+    if (!virtio_test_backend_virtio_1(vdev, errp)) {
+        virtio_pci_disable_modern(proxy);
+    }
+
+    legacy = virtio_pci_legacy(proxy);
+    modern = virtio_pci_modern(proxy);
+    if (!legacy && !modern) {
+        error_setg(errp, "PCI device is neither legacy nor modern.");
+        return;
+    }
+
     config = proxy->pci_dev.config;
     if (proxy->class_code) {
         pci_config_set_class(config, proxy->class_code);
diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
index 25fbf8a..4e976b3 100644
--- a/hw/virtio/virtio-pci.h
+++ b/hw/virtio/virtio-pci.h
@@ -172,6 +172,11 @@ static inline void virtio_pci_force_virtio_1(VirtIOPCIProxy *proxy)
     proxy->disable_legacy = ON_OFF_AUTO_ON;
 }
 
+static inline void virtio_pci_disable_modern(VirtIOPCIProxy *proxy)
+{
+    proxy->disable_modern = true;
+}
+
 /*
  * virtio-scsi-pci: This extends VirtioPCIProxy.
  */
-- 
2.7.4