4 files changed, 47 insertions, 18 deletions

diff --git a/hw/virtio/virtio-crypto-pci.c b/hw/virtio/virtio-crypto-pci.c
index 90a6e0d..13807e5 100644
--- a/hw/virtio/virtio-crypto-pci.c
+++ b/hw/virtio/virtio-crypto-pci.c
@@ -51,7 +51,9 @@ static void virtio_crypto_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
     }
 
     qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
-    virtio_pci_force_virtio_1(vpci_dev);
+    if (!virtio_pci_force_virtio_1(vpci_dev, errp)) {
+        return;
+    }
     object_property_set_bool(OBJECT(vdev), true, "realized", errp);
     object_property_set_link(OBJECT(vcrypto),
                  OBJECT(vcrypto->vdev.conf.cryptodev), "cryptodev",
diff --git a/hw/virtio/virtio-input-pci.c b/hw/virtio/virtio-input-pci.c
index 2c13978..2847772 100644
--- a/hw/virtio/virtio-input-pci.c
+++ b/hw/virtio/virtio-input-pci.c
@@ -48,7 +48,9 @@ static void virtio_input_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
     DeviceState *vdev = DEVICE(&vinput->vdev);
 
     qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
-    virtio_pci_force_virtio_1(vpci_dev);
+    if (!virtio_pci_force_virtio_1(vpci_dev, errp)) {
+        return;
+    }
     object_property_set_bool(OBJECT(vdev), true, "realized", errp);
 }
 
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index cb44e19..509c1ff 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1721,16 +1721,22 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
                        /* PCI BAR regions must be powers of 2 */
                        pow2ceil(proxy->notify.offset + proxy->notify.size));
 
-    if (proxy->disable_legacy == ON_OFF_AUTO_AUTO) {
-        proxy->disable_legacy = pcie_port ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
-    }
-
-    if (!virtio_pci_modern(proxy) && !virtio_pci_legacy(proxy)) {
-        error_setg(errp, "device cannot work as neither modern nor legacy mode"
-                   " is enabled");
-        error_append_hint(errp, "Set either disable-modern or disable-legacy"
-                          " to off\n");
-        return;
+    if ((proxy->disable_legacy == ON_OFF_AUTO_ON) ||
+        ((proxy->disable_legacy == ON_OFF_AUTO_AUTO) && pcie_port)) {
+        if (proxy->disable_modern) {
+            error_setg(errp, "device cannot work as neither modern nor "
+                       "legacy mode is enabled");
+            error_append_hint(errp, "Set either disable-modern or "
+                              "disable-legacy to off\n");
+            return;
+        }
+        proxy->mode = VIRTIO_PCI_MODE_MODERN;
+    } else {
+        if (proxy->disable_modern) {
+            proxy->mode = VIRTIO_PCI_MODE_LEGACY;
+        } else {
+            proxy->mode = VIRTIO_PCI_MODE_TRANSITIONAL;
+        }
     }
 
     if (pcie_port && pci_is_express(pci_dev)) {
diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
index 1858185..bfea289 100644
--- a/hw/virtio/virtio-pci.h
+++ b/hw/virtio/virtio-pci.h
@@ -15,6 +15,7 @@
 #ifndef QEMU_VIRTIO_PCI_H
 #define QEMU_VIRTIO_PCI_H
 
+#include "qapi/error.h"
 #include "hw/pci/msi.h"
 #include "hw/virtio/virtio-bus.h"
 
@@ -118,6 +119,12 @@ typedef struct VirtIOPCIQueue {
   uint32_t used[2];
 } VirtIOPCIQueue;
 
+typedef enum {
+    VIRTIO_PCI_MODE_LEGACY,
+    VIRTIO_PCI_MODE_TRANSITIONAL,
+    VIRTIO_PCI_MODE_MODERN,
+} VirtIOPCIMode;
+
 struct VirtIOPCIProxy {
     PCIDevice pci_dev;
     MemoryRegion bar;
@@ -142,6 +149,7 @@ struct VirtIOPCIProxy {
     bool disable_modern;
     bool ignore_backend_features;
     OnOffAuto disable_legacy;
+    VirtIOPCIMode mode;
     uint32_t class_code;
     uint32_t nvectors;
     uint32_t dfselect;
@@ -156,23 +164,34 @@ struct VirtIOPCIProxy {
 
 static inline bool virtio_pci_modern(VirtIOPCIProxy *proxy)
 {
-    return !proxy->disable_modern;
+    return proxy->mode != VIRTIO_PCI_MODE_LEGACY;
 }
 
 static inline bool virtio_pci_legacy(VirtIOPCIProxy *proxy)
 {
-    return proxy->disable_legacy == ON_OFF_AUTO_OFF;
+    return proxy->mode != VIRTIO_PCI_MODE_MODERN;
 }
 
-static inline void virtio_pci_force_virtio_1(VirtIOPCIProxy *proxy)
+static inline bool virtio_pci_force_virtio_1(VirtIOPCIProxy *proxy,
+                                             Error **errp)
 {
-    proxy->disable_modern = false;
-    proxy->disable_legacy = ON_OFF_AUTO_ON;
+    if (proxy->disable_legacy == ON_OFF_AUTO_OFF) {
+        error_setg(errp, "Unable to set disable-legacy=off on a virtio-1.0 "
+                   "only device");
+        return false;
+    }
+    if (proxy->disable_modern == true) {
+        error_setg(errp, "Unable to set disable-modern=on on a virtio-1.0 "
+                   "only device");
+        return false;
+    }
+    proxy->mode = VIRTIO_PCI_MODE_MODERN;
+    return true;
 }
 
 static inline void virtio_pci_disable_modern(VirtIOPCIProxy *proxy)
 {
-    proxy->disable_modern = true;
+    proxy->mode = VIRTIO_PCI_MODE_LEGACY;
 }
 
 /*