hw/arm/aspeed: Check for CPU types in machine_run_board_init()

[mirror_qemu.git] / docs / interop / nbd.txt

diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt
index f3b3cacc96214b1ef7834b14771cbb83c415a872..18efb251de9160bd04d94620bc610b49ab02b3a4 100644 (file)
--- a/docs/interop/nbd.txt
+++ b/docs/interop/nbd.txt
@@ -1,4 +1,4 @@
-Qemu supports the NBD protocol, and has an internal NBD client (see
+QEMU supports the NBD protocol, and has an internal NBD client (see
 block/nbd.c), an internal NBD server (see blockdev-nbd.c), and an
 external NBD server tool (see qemu-nbd.c). The common code is placed
 in nbd/*.
@@ -7,29 +7,41 @@ The NBD protocol is specified here:
 https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md
 
 The following paragraphs describe some specific properties of NBD
-protocol realization in Qemu.
+protocol realization in QEMU.
 
 = Metadata namespaces =
 
-Qemu supports the "base:allocation" metadata context as defined in the
+QEMU supports the "base:allocation" metadata context as defined in the
 NBD protocol specification, and also defines an additional metadata
 namespace "qemu".
 
 == "qemu" namespace ==
 
-The "qemu" namespace currently contains only one type of context,
-related to exposing the contents of a dirty bitmap alongside the
-associated disk contents.  That context has the following form:
+The "qemu" namespace currently contains two available metadata context
+types.  The first is related to exposing the contents of a dirty
+bitmap alongside the associated disk contents.  That metadata context
+is named with the following form:
 
     qemu:dirty-bitmap:<dirty-bitmap-export-name>
 
 Each dirty-bitmap metadata context defines only one flag for extents
 in reply for NBD_CMD_BLOCK_STATUS:
 
-    bit 0: NBD_STATE_DIRTY, means that the extent is "dirty"
+    bit 0: NBD_STATE_DIRTY, set when the extent is "dirty"
+
+The second is related to exposing the source of various extents within
+the image, with a single metadata context named:
+
+    qemu:allocation-depth
+
+In the allocation depth context, the entire 32-bit value represents a
+depth of which layer in a thin-provisioned backing chain provided the
+data (0 for unallocated, 1 for the active layer, 2 for the first
+backing layer, and so forth).
 
 For NBD_OPT_LIST_META_CONTEXT the following queries are supported
-in addition to "qemu:dirty-bitmap:<dirty-bitmap-export-name>":
+in addition to the specific "qemu:allocation-depth" and
+"qemu:dirty-bitmap:<dirty-bitmap-export-name>":
 
 * "qemu:" - returns list of all available metadata contexts in the
             namespace.
@@ -55,3 +67,6 @@ the operation of that feature.
 NBD_CMD_BLOCK_STATUS for "qemu:dirty-bitmap:", NBD_CMD_CACHE
 * 4.2: NBD_FLAG_CAN_MULTI_CONN for shareable read-only exports,
 NBD_CMD_FLAG_FAST_ZERO
+* 5.2: NBD_CMD_BLOCK_STATUS for "qemu:allocation-depth"
+* 7.1: NBD_FLAG_CAN_MULTI_CONN for shareable writable exports
+* 8.2: NBD_OPT_EXTENDED_HEADERS, NBD_FLAG_BLOCK_STATUS_PAYLOAD