virtio: introduce extended features

The virtio specifications allows for up to 128 bits for the
device features. Soon we are going to use some of the 'extended'
bits features (above 64) for the virtio_net driver.

Introduce extended features as a fixed size array of u64. To minimize
the diffstat allows legacy driver to access the low 64 bits via a
transparent union.

Introduce an extended get_extended_features configuration callback
that devices supporting the extended features range must implement in
place of the traditional one.

Note that legacy and transport features don't need any change, as
they are always in the low 64 bit range.

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

2 files changed, 41 insertions, 29 deletions

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 95d5d7993e5b..5c48788cdbec 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -53,7 +53,7 @@ static ssize_t features_show(struct device *_d,
 
 	/* We actually represent this as a bitstring, as it could be
 	 * arbitrary length in future. */
-	for (i = 0; i < sizeof(dev->features)*8; i++)
+	for (i = 0; i < VIRTIO_FEATURES_MAX; i++)
 		len += sysfs_emit_at(buf, len, "%c",
 			       __virtio_test_bit(dev, i) ? '1' : '0');
 	len += sysfs_emit_at(buf, len, "\n");
@@ -272,22 +272,22 @@ static int virtio_dev_probe(struct device *_d)
 	int err, i;
 	struct virtio_device *dev = dev_to_virtio(_d);
 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
-	u64 device_features;
-	u64 driver_features;
+	u64 device_features[VIRTIO_FEATURES_DWORDS];
+	u64 driver_features[VIRTIO_FEATURES_DWORDS];
 	u64 driver_features_legacy;
 
 	/* We have a driver! */
 	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
 
 	/* Figure out what features the device supports. */
-	device_features = dev->config->get_features(dev);
+	virtio_get_features(dev, device_features);
 
 	/* Figure out what features the driver supports. */
-	driver_features = 0;
+	virtio_features_zero(driver_features);
 	for (i = 0; i < drv->feature_table_size; i++) {
 		unsigned int f = drv->feature_table[i];
-		BUG_ON(f >= 64);
-		driver_features |= (1ULL << f);
+		if (!WARN_ON_ONCE(f >= VIRTIO_FEATURES_MAX))
+			virtio_features_set_bit(driver_features, f);
 	}
 
 	/* Some drivers have a separate feature table for virtio v1.0 */
@@ -295,24 +295,29 @@ static int virtio_dev_probe(struct device *_d)
 		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);
+			if (!WARN_ON_ONCE(f >= 64))
+				driver_features_legacy |= (1ULL << f);
 		}
 	} else {
-		driver_features_legacy = driver_features;
+		driver_features_legacy = driver_features[0];
 	}
 
-	if (device_features & (1ULL << VIRTIO_F_VERSION_1))
-		dev->features = driver_features & device_features;
-	else
-		dev->features = driver_features_legacy & device_features;
+	if (virtio_features_test_bit(device_features, VIRTIO_F_VERSION_1)) {
+		for (i = 0; i < VIRTIO_FEATURES_DWORDS; ++i)
+			dev->features_array[i] = driver_features[i] &
+						 device_features[i];
+	} else {
+		virtio_features_from_u64(dev->features_array,
+					 driver_features_legacy &
+					 device_features[0]);
+	}
 
 	/* When debugging, user may filter some features by hand. */
 	virtio_debug_device_filter_features(dev);
 
 	/* Transport features always preserved to pass to finalize_features. */
 	for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++)
-		if (device_features & (1ULL << i))
+		if (virtio_features_test_bit(device_features, i))
 			__virtio_set_bit(dev, i);
 
 	err = dev->config->finalize_features(dev);
@@ -320,14 +325,15 @@ static int virtio_dev_probe(struct device *_d)
 		goto err;
 
 	if (drv->validate) {
-		u64 features = dev->features;
+		u64 features[VIRTIO_FEATURES_DWORDS];
 
+		virtio_features_copy(features, dev->features_array);
 		err = drv->validate(dev);
 		if (err)
 			goto err;
 
 		/* Did validation change any features? Then write them again. */
-		if (features != dev->features) {
+		if (!virtio_features_equal(features, dev->features_array)) {
 			err = dev->config->finalize_features(dev);
 			if (err)
 				goto err;
@@ -701,6 +707,9 @@ EXPORT_SYMBOL_GPL(virtio_device_reset_done);
 
 static int virtio_init(void)
 {
+	BUILD_BUG_ON(offsetof(struct virtio_device, features) !=
+		     offsetof(struct virtio_device, features_array[0]));
+
 	if (bus_register(&virtio_bus) != 0)
 		panic("virtio bus registration failed");
 	virtio_debug_init();
diff --git a/drivers/virtio/virtio_debug.c b/drivers/virtio/virtio_debug.c
index 95c8fc7705bb..d58713ddf2e5 100644
--- a/drivers/virtio/virtio_debug.c
+++ b/drivers/virtio/virtio_debug.c
@@ -8,13 +8,13 @@ static struct dentry *virtio_debugfs_dir;
 
 static int virtio_debug_device_features_show(struct seq_file *s, void *data)
 {
+	u64 device_features[VIRTIO_FEATURES_DWORDS];
 	struct virtio_device *dev = s->private;
-	u64 device_features;
 	unsigned int i;
 
-	device_features = dev->config->get_features(dev);
-	for (i = 0; i < BITS_PER_LONG_LONG; i++) {
-		if (device_features & (1ULL << i))
+	virtio_get_features(dev, device_features);
+	for (i = 0; i < VIRTIO_FEATURES_MAX; i++) {
+		if (virtio_features_test_bit(device_features, i))
 			seq_printf(s, "%u\n", i);
 	}
 	return 0;
@@ -26,8 +26,8 @@ static int virtio_debug_filter_features_show(struct seq_file *s, void *data)
 	struct virtio_device *dev = s->private;
 	unsigned int i;
 
-	for (i = 0; i < BITS_PER_LONG_LONG; i++) {
-		if (dev->debugfs_filter_features & (1ULL << i))
+	for (i = 0; i < VIRTIO_FEATURES_MAX; i++) {
+		if (virtio_features_test_bit(dev->debugfs_filter_features, i))
 			seq_printf(s, "%u\n", i);
 	}
 	return 0;
@@ -39,7 +39,7 @@ static int virtio_debug_filter_features_clear(void *data, u64 val)
 	struct virtio_device *dev = data;
 
 	if (val == 1)
-		dev->debugfs_filter_features = 0;
+		virtio_features_zero(dev->debugfs_filter_features);
 	return 0;
 }
 
@@ -50,9 +50,10 @@ static int virtio_debug_filter_feature_add(void *data, u64 val)
 {
 	struct virtio_device *dev = data;
 
-	if (val >= BITS_PER_LONG_LONG)
+	if (val >= VIRTIO_FEATURES_MAX)
 		return -EINVAL;
-	dev->debugfs_filter_features |= BIT_ULL_MASK(val);
+
+	virtio_features_set_bit(dev->debugfs_filter_features, val);
 	return 0;
 }
 
@@ -63,9 +64,10 @@ static int virtio_debug_filter_feature_del(void *data, u64 val)
 {
 	struct virtio_device *dev = data;
 
-	if (val >= BITS_PER_LONG_LONG)
+	if (val >= VIRTIO_FEATURES_MAX)
 		return -EINVAL;
-	dev->debugfs_filter_features &= ~BIT_ULL_MASK(val);
+
+	virtio_features_clear_bit(dev->debugfs_filter_features, val);
 	return 0;
 }
 
@@ -91,7 +93,8 @@ EXPORT_SYMBOL_GPL(virtio_debug_device_init);
 
 void virtio_debug_device_filter_features(struct virtio_device *dev)
 {
-	dev->features &= ~dev->debugfs_filter_features;
+	virtio_features_andnot(dev->features_array, dev->features_array,
+			       dev->debugfs_filter_features);
 }
 EXPORT_SYMBOL_GPL(virtio_debug_device_filter_features);