[RFC PATCH 5/5] hw/block/nvme: add namespace sharing param for mpath

[Minwoo Im <minwoo.im.dev@gmail.com>]

Added mpath.ns parameter to set multi-namespace bit[0] in NMIC field in
Identify Namespace data structure.  It will indicate that the namespace
can be shared by two or more controllers.

Example:

  To share the namespace between two controllers in a NVM subsystem,
first multi-controllers should be prepared with the same serial:

  -device nvme,id=nvme0,ctrlid=0,serial=foo,...
  -device nvme,id=nvme1,ctrlid=1,serial=foo,...

Then, we can prepare namespace device with mpath.ns enabled.  Also, we
must give the same UUID for those two devices with the same Namespace
ID.

  -device nvme-ns,uuid=<uuid>,bus=nvme0,nsid=1,...
  -device nvme-ns,uuid=<uuid>,bus=nvme1,nsid=1,...

Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
---
 hw/block/nvme-ns.c | 14 ++++++++++++--
 hw/block/nvme-ns.h |  2 ++
 hw/block/nvme.c    |  6 ++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/hw/block/nvme-ns.c b/hw/block/nvme-ns.c
index 274eaf61b721..cedacda9ebab 100644
--- a/hw/block/nvme-ns.c
+++ b/hw/block/nvme-ns.c
@@ -32,13 +32,18 @@
 
 #define MIN_DISCARD_GRANULARITY (4 * KiB)
 
-static int nvme_ns_init(NvmeNamespace *ns, Error **errp)
+static int nvme_ns_init(NvmeCtrl *n, NvmeNamespace *ns, Error **errp)
 {
     BlockDriverInfo bdi;
     NvmeIdNs *id_ns = &ns->id_ns;
     int lba_index = NVME_ID_NS_FLBAS_INDEX(ns->id_ns.flbas);
     int npdg;
 
+    if (!n->params.mpath_ctrl && ns->params.mpath_ns) {
+        error_setg(errp, "mpath.ctrl must be enabled for ns sharing");
+        return -1;
+    }
+
     ns->id_ns.dlfeat = 0x9;
 
     id_ns->lbaf[lba_index].ds = 31 - clz32(ns->blkconf.logical_block_size);
@@ -63,6 +68,10 @@ static int nvme_ns_init(NvmeNamespace *ns, Error **errp)
 
     id_ns->npda = id_ns->npdg = npdg - 1;
 
+    if (ns->params.mpath_ns) {
+        id_ns->nmic |= NVME_NMIC_NS_SHARED;
+    }
+
     return 0;
 }
 
@@ -314,7 +323,7 @@ int nvme_ns_setup(NvmeCtrl *n, NvmeNamespace *ns, Error **errp)
         return -1;
     }
 
-    if (nvme_ns_init(ns, errp)) {
+    if (nvme_ns_init(n, ns, errp)) {
         return -1;
     }
     if (ns->params.zoned) {
@@ -371,6 +380,7 @@ static Property nvme_ns_props[] = {
     DEFINE_BLOCK_PROPERTIES(NvmeNamespace, blkconf),
     DEFINE_PROP_UINT32("nsid", NvmeNamespace, params.nsid, 0),
     DEFINE_PROP_UUID("uuid", NvmeNamespace, params.uuid),
+    DEFINE_PROP_BOOL("mpath.ns", NvmeNamespace, params.mpath_ns, false),
     DEFINE_PROP_BOOL("zoned", NvmeNamespace, params.zoned, false),
     DEFINE_PROP_SIZE("zoned.zone_size", NvmeNamespace, params.zone_size_bs,
                      NVME_DEFAULT_ZONE_SIZE),
diff --git a/hw/block/nvme-ns.h b/hw/block/nvme-ns.h
index f8f3c28c360b..d1f2518f7210 100644
--- a/hw/block/nvme-ns.h
+++ b/hw/block/nvme-ns.h
@@ -29,6 +29,8 @@ typedef struct NvmeNamespaceParams {
     uint32_t nsid;
     QemuUUID uuid;
 
+    bool     mpath_ns;
+
     bool     zoned;
     bool     cross_zone_read;
     uint64_t zone_size_bs;
diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index 50b349cf9ea3..e4aa15345c12 100644
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -62,6 +62,12 @@
  *   can hold two or more controllers.  This will be reflected to Identify
  *   Controller data structure CMIC[76] field.
  *
+ * Setting `mpath.ctrl` to true enables the following properties to configure
+ * multi-path for a namespace:
+ *     mpath.ns=<true|false, default: false>
+ *         If set to true, namespace sharing in a NVM subsystem is enabled.
+ *         This will be reflected to Identify Namespace data structure.
+ *
  * - `zoned.append_size_limit`
  *   The maximum I/O size in bytes that is allowed in Zone Append command.
  *   The default is 128KiB. Since internally this this value is maintained as
-- 
2.17.1