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-rw-r--r--virtio-v1.0-wd01-part1-specification.txt18
1 files changed, 16 insertions, 2 deletions
diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt
index 1ea7a52..36f630c 100644
--- a/virtio-v1.0-wd01-part1-specification.txt
+++ b/virtio-v1.0-wd01-part1-specification.txt
@@ -2226,6 +2226,9 @@ device except where noted.
VIRTIO_BLK_F_FLUSH (9) Cache flush command support.
+ VIRTIO_BLK_F_TOPOLOGY (10) Device exports information on optimal I/O
+ alignment.
+
2.4.2.3.1 Legacy Interface: Feature bits
--------------------
VIRTIO_BLK_F_BARRIER (0) Host supports request barriers.
@@ -2249,6 +2252,12 @@ bits as indicated above.
u8 sectors;
} geometry;
u32 blk_size;
+ struct virtio_blk_topology {
+ u8 physical_block_exp;
+ u8 alignment_offset;
+ u16 min_io_size;
+ u32 opt_io_size;
+ } topology;
};
@@ -2261,13 +2270,18 @@ bits as indicated above.
2. If the VIRTIO_BLK_F_BLK_SIZE feature is negotiated, the
blk_size field can be read to determine the optimal sector size
- for the driver to use. This does not effect the units used in
+ for the driver to use. This does not affect the units used in
the protocol (always 512 bytes), but awareness of the correct
- value can effect performance.
+ value can affect performance.
3. If the VIRTIO_BLK_F_RO feature is set by the device, any write
requests will fail.
+4. If the VIRTIO_BLK_F_TOPOLOGY feature is negotiated, the fields in the
+ topology struct can be read to determine the physical block size and optimal
+ I/O lengths for the driver to use. This also does not affect the units
+ in the protocol, only performance.
+
2.4.2.5. Device Operation
------------------------