[Qemu-devel] [PATCH 1/2] virtio: allow per-device-class legacy features

["Michael S. Tsirkin" <mst@redhat.com>]

Legacy features are those that transitional devices only
expose on the legacy interface.
Allow different ones per device class.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/virtio.h | 5 +++++
 hw/s390x/virtio-ccw.c      | 4 +++-
 hw/virtio/virtio-pci.c     | 4 +++-
 hw/virtio/virtio.c         | 2 ++
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index f12a1a8..bdb3c4b 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -113,6 +113,11 @@ typedef struct VirtioDeviceClass {
     void (*set_config)(VirtIODevice *vdev, const uint8_t *config);
     void (*reset)(VirtIODevice *vdev);
     void (*set_status)(VirtIODevice *vdev, uint8_t val);
+    /* For transitional devices, this is a bitmap of features
+     * that are only exposed on the legacy interface but not
+     * the modern one.
+     */
+    uint64_t legacy_features;
     /* Test and clear event pending status.
      * Should be called after unmask to avoid losing events.
      * If backend does not support masking,
diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index 7d7f8f6..f5c1d98 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -303,6 +303,8 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
         if (!ccw.cda) {
             ret = -EFAULT;
         } else {
+            VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
+
             features.index = address_space_ldub(&address_space_memory,
                                                 ccw.cda
                                                 + sizeof(features.features),
@@ -312,7 +314,7 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
                 if (dev->revision >= 1) {
                     /* Don't offer legacy features for modern devices. */
                     features.features = (uint32_t)
-                        (vdev->host_features & ~VIRTIO_LEGACY_FEATURES);
+                        (vdev->host_features & ~vdc->legacy_features);
                 } else {
                     features.features = (uint32_t)vdev->host_features;
                 }
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 62001b4..97b32fe 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1175,7 +1175,9 @@ static uint64_t virtio_pci_common_read(void *opaque, hwaddr addr,
         break;
     case VIRTIO_PCI_COMMON_DF:
         if (proxy->dfselect <= 1) {
-            val = (vdev->host_features & ~VIRTIO_LEGACY_FEATURES) >>
+            VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
+
+            val = (vdev->host_features & ~vdc->legacy_features) >>
                 (32 * proxy->dfselect);
         }
         break;
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 1df5f4e..72ee06b 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2214,6 +2214,8 @@ static void virtio_device_class_init(ObjectClass *klass, void *data)
     dc->props = virtio_properties;
     vdc->start_ioeventfd = virtio_device_start_ioeventfd_impl;
     vdc->stop_ioeventfd = virtio_device_stop_ioeventfd_impl;
+
+    vdc->legacy_features |= VIRTIO_LEGACY_FEATURES;
 }
 
 bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev)
-- 
MST