[PATCH v7 14/46] virtio: add legacy feature table support

Michael S. Tsirkin
2014-11-30T15:10:49Z

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>
---
include/linux/virtio.h | 4 ++++
drivers/virtio/virtio.c | 25 ++++++++++++++++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index d6359a5..f70411e 100644
--- 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);
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 3e78f4b..f9ad99c 100644
--- 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++)
--
MST