svn commit: r246061 - projects/virtio/sys/dev/virtio/block

[Bryan Venteicher]

Author: bryanv
Date: Tue Jan 29 07:35:25 2013
New Revision: 246061
URL: http://svnweb.freebsd.org/changeset/base/246061

Log:
  virtio_blk: Do not always read entire config
  
  Only the capacity is guaranteed to be available. The other fields
  in the device config should only be read if their corresponding
  feature was negotiated.
  
  Approved by:	grehan (implicit)

Modified:
  projects/virtio/sys/dev/virtio/block/virtio_blk.c

Modified: projects/virtio/sys/dev/virtio/block/virtio_blk.c
==============================================================================
--- projects/virtio/sys/dev/virtio/block/virtio_blk.c	Tue Jan 29 07:33:40 2013	(r246060)
+++ projects/virtio/sys/dev/virtio/block/virtio_blk.c	Tue Jan 29 07:35:25 2013	(r246061)
@@ -138,6 +138,8 @@ static void	vtblk_vq_intr(void *);
 
 static void	vtblk_stop(struct vtblk_softc *);
 
+static void	vtblk_read_config(struct vtblk_softc *,
+		    struct virtio_blk_config *);
 static void	vtblk_get_ident(struct vtblk_softc *);
 static void	vtblk_prepare_dump(struct vtblk_softc *);
 static int	vtblk_write_dump(struct vtblk_softc *, void *, off_t, size_t);
@@ -283,8 +285,7 @@ vtblk_attach(device_t dev)
 		sc->vtblk_flags |= VTBLK_FLAG_READONLY;
 
 	/* Get local copy of config. */
-	virtio_read_device_config(dev, 0, &blkcfg,
-	    sizeof(struct virtio_blk_config));
+	vtblk_read_config(sc, &blkcfg);
 
 	/*
 	 * With the current sglist(9) implementation, it is not easy
@@ -428,8 +429,7 @@ vtblk_config_change(device_t dev)
 
 	sc = device_get_softc(dev);
 
-	virtio_read_device_config(dev, 0, &blkcfg,
-	    sizeof(struct virtio_blk_config));
+	vtblk_read_config(sc, &blkcfg);
 
 	/* Capacity is always in 512-byte units. */
 	capacity = blkcfg.capacity * 512;
@@ -878,6 +878,36 @@ vtblk_stop(struct vtblk_softc *sc)
 	virtio_stop(sc->vtblk_dev);
 }
 
+#define VTBLK_GET_CONFIG(_dev, _feature, _field, _cfg)			\
+	if (virtio_with_feature(_dev, _feature)) {			\
+		virtio_read_device_config(_dev,				\
+		    offsetof(struct virtio_blk_config, _field), 	\
+		    &(_cfg)->_field, sizeof((_cfg)->_field));		\
+	}
+
+static void
+vtblk_read_config(struct vtblk_softc *sc, struct virtio_blk_config *blkcfg)
+{
+	device_t dev;
+
+	dev = sc->vtblk_dev;
+
+	bzero(blkcfg, sizeof(struct virtio_blk_config));
+
+	/* The capacity is always available. */
+	virtio_read_device_config(dev, offsetof(struct virtio_blk_config,
+	    capacity), &blkcfg->capacity, 8);
+
+	/* Read the configuration if the feature was negotiated. */
+	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_SIZE_MAX, size_max, blkcfg);
+	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_SEG_MAX, seg_max, blkcfg);
+	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_GEOMETRY, geometry, blkcfg);
+	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_BLK_SIZE, blk_size, blkcfg);
+	VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_TOPOLOGY, topology, blkcfg);
+}
+
+#undef VTBLK_GET_CONFIG
+
 static void
 vtblk_get_ident(struct vtblk_softc *sc)
 {