virtio: add legacy feature table support

virtio-blk has some legacy feature bits that modern drivers
must not negotiate, but are needed for old legacy hosts
(that e.g. don't support virtio-scsi).
Allow a separate legacy feature table for such cases.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 3e78f4bcfa8efac83afd778fe85834d5707d5431..f9ad99c8b35241681393670801f5aaa037cd6538 100644 (file)
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -113,6 +113,13 @@ void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
        for (i = 0; i < drv->feature_table_size; i++)
                if (drv->feature_table[i] == fbit)
                        return;
+
+       if (drv->feature_table_legacy) {
+               for (i = 0; i < drv->feature_table_size_legacy; i++)
+                       if (drv->feature_table_legacy[i] == fbit)
+                               return;
+       }
+
        BUG();
 }
 EXPORT_SYMBOL_GPL(virtio_check_driver_offered_feature);
@@ -161,6 +168,7 @@ static int virtio_dev_probe(struct device *_d)
        struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
        u64 device_features;
        u64 driver_features;
+       u64 driver_features_legacy;
        unsigned status;
 
        /* We have a driver! */
@@ -177,7 +185,22 @@ static int virtio_dev_probe(struct device *_d)
                driver_features |= (1ULL << f);
        }
 
-       dev->features = driver_features & device_features;
+       /* Some drivers have a separate feature table for virtio v1.0 */
+       if (drv->feature_table_legacy) {
+               driver_features_legacy = 0;
+               for (i = 0; i < drv->feature_table_size_legacy; i++) {
+                       unsigned int f = drv->feature_table_legacy[i];
+                       BUG_ON(f >= 64);
+                       driver_features_legacy |= (1ULL << f);
+               }
+       } else {
+               driver_features_legacy = driver_features;
+       }
+
+       if (driver_features & device_features & (1ULL << VIRTIO_F_VERSION_1))
+               dev->features = driver_features & device_features;
+       else
+               dev->features = driver_features_legacy & device_features;
 
        /* Transport features always preserved to pass to finalize_features. */
        for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++)

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index d6359a5d5d4e22f1ff20fffde97a0ae958047d82..f70411eb9d27a9feec55232f63550f008190b81f 100644 (file)
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -130,6 +130,8 @@ int virtio_device_restore(struct virtio_device *dev);
  * @id_table: the ids serviced by this driver.
  * @feature_table: an array of feature numbers supported by this driver.
  * @feature_table_size: number of entries in the feature table array.
+ * @feature_table_legacy: same as feature_table but when working in legacy mode.
+ * @feature_table_size_legacy: number of entries in feature table legacy array.
  * @probe: the function to call when a device is found.  Returns 0 or -errno.
  * @remove: the function to call when a device is removed.
  * @config_changed: optional function to call when the device configuration
@@ -140,6 +142,8 @@ struct virtio_driver {
        const struct virtio_device_id *id_table;
        const unsigned int *feature_table;
        unsigned int feature_table_size;
+       const unsigned int *feature_table_legacy;
+       unsigned int feature_table_size_legacy;
        int (*probe)(struct virtio_device *dev);
        void (*scan)(struct virtio_device *dev);
        void (*remove)(struct virtio_device *dev);