On Tue, Nov 25, 2014 at 06:53:42PM +0100, Cornelia Huck wrote:

On Tue, 25 Nov 2014 18:42:09 +0200
"Michael S. Tsirkin" [off-list ref] wrote:

quoted

virtio blk has some legacy feature bits that modern drivers

virtio-blk

quoted

must not negotiate, but are needed for old legacy hosts
(e.g. that dn't support virtio scsi).

(that e.g. don't support virtio-scsi)

quoted

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(-)

quoted

@@ -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 tables for virtio v1.0 */

/* some drivers have a separate feature table for legacy virtio */

?

I prefer have separate feature tables:  drivers (plural) have tables
(plural).

Agree?

quoted

+	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;
+	}

(...)