virtio_blk: add block topology support
Allow reading various alignment values from the config page. This
allows the guest to much better align I/O requests depending on the
storage topology.
Note that the formats for the config values appear a bit messed up,
but we follow the formats used by ATA and SCSI so they are expected in
the storage world.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/include/linux/virtio_blk.h b/include/linux/virtio_blk.h
index fd294c5..e52029e 100644
--- a/include/linux/virtio_blk.h
+++ b/include/linux/virtio_blk.h
@@ -15,6 +15,7 @@
#define VIRTIO_BLK_F_BLK_SIZE 6 /* Block size of disk is available*/
#define VIRTIO_BLK_F_SCSI 7 /* Supports scsi command passthru */
#define VIRTIO_BLK_F_FLUSH 9 /* Cache flush command support */
+#define VIRTIO_BLK_F_TOPOLOGY 10 /* Topology information is available */
struct virtio_blk_config {
/* The capacity (in 512-byte sectors). */
@@ -29,8 +30,20 @@
__u8 heads;
__u8 sectors;
} geometry;
+
/* block size of device (if VIRTIO_BLK_F_BLK_SIZE) */
__u32 blk_size;
+
+ /* the next 4 entries are guarded by VIRTIO_BLK_F_TOPOLOGY */
+ /* exponent for physical block per logical block. */
+ __u8 physical_block_exp;
+ /* alignment offset in logical blocks. */
+ __u8 alignment_offset;
+ /* minimum I/O size without performance penalty in logical blocks. */
+ __u16 min_io_size;
+ /* optimal sustained I/O size in logical blocks. */
+ __u32 opt_io_size;
+
} __attribute__((packed));
/*