virtio: add virtio disk geometry feature

Rather than faking up some geometry, allow the backend to push the disk
geometry via virtio pci config option.  Keep the old geo code around for
compatibility.

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (modified to single struct)

1 files changed, 20 insertions, 4 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 78be6b8c89e0..84e064ffee52 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -157,10 +157,25 @@ static int virtblk_ioctl(struct inode *inode, struct file *filp,
 /* We provide getgeo only to please some old bootloader/partitioning tools */
 static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
 {
-        /* some standard values, similar to sd */
-        geo->heads = 1 << 6;
-        geo->sectors = 1 << 5;
-        geo->cylinders = get_capacity(bd->bd_disk) >> 11;
+        struct virtio_blk *vblk = bd->bd_disk->private_data;
+        struct virtio_blk_geometry vgeo;
+        int err;
+
+        /* see if the host passed in geometry config */
+        err = virtio_config_val(vblk->vdev, VIRTIO_BLK_F_GEOMETRY,
+                                offsetof(struct virtio_blk_config, geometry),
+                                &vgeo);
+
+        if (!err) {
+                geo->heads = vgeo.heads;
+                geo->sectors = vgeo.sectors;
+                geo->cylinders = vgeo.cylinders;
+        } else {
+                /* some standard values, similar to sd */
+                geo->heads = 1 << 6;
+                geo->sectors = 1 << 5;
+                geo->cylinders = get_capacity(bd->bd_disk) >> 11;
+        }
         return 0;
 }
 
@@ -310,6 +325,7 @@ static struct virtio_device_id id_table[] = {
 
 static unsigned int features[] = {
         VIRTIO_BLK_F_BARRIER, VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX,
+        VIRTIO_BLK_F_GEOMETRY,
 };
 
 static struct virtio_driver virtio_blk = {