Block driver using virtio.

The block driver uses scatter-gather lists with sg[0] being the
request information (struct virtio_blk_outhdr) with the type, sector
and inbuf id.  The next N sg entries are the bio itself, then the last
sg is the status byte.  Whether the N entries are in or out depends on
whether it's a read or a write.

We accept the normal (SCSI) ioctls: they get handed through to the other
side which can then handle it or reply that it's unsupported.  It's
not clear that this actually works in general, since I don't know
if blk_pc_request() requests have an accurate rq_data_dir().

Although we try to reply -ENOTTY on unsupported commands, ioctl(fd,
CDROMEJECT) returns success to userspace.  This needs a separate
patch.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index ce4b1e484e64..4d0119ea9e35 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -425,4 +425,10 @@ config XEN_BLKDEV_FRONTEND
           block device driver.  It communicates with a back-end driver
           in another domain which drives the actual block device.
 
+config VIRTIO_BLK
+        tristate "Virtio block driver (EXPERIMENTAL)"
+        depends on EXPERIMENTAL && VIRTIO
+        ---help---
+          This is the virtual block driver for lguest.  Say Y or M.
+
 endif # BLK_DEV