hw/nvme: change nvme-ns 'shared' default

Change namespaces to be shared namespaces by default (parameter
shared=on). Keep shared=off for older machine types.

Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>

docs/system/devices/nvme.rst

@@ -110,28 +110,32 @@ multipath I/O.
 This will create an NVM subsystem with two controllers. Having controllers
 linked to an ``nvme-subsys`` device allows additional ``nvme-ns`` parameters:
 
-``shared`` (default: ``off``)
+``shared`` (default: ``on`` since 6.2)
   Specifies that the namespace will be attached to all controllers in the
-  subsystem. If set to ``off`` (the default), the namespace will remain a
+  subsystem. If set to ``off``, the namespace will remain a private namespace
-  private namespace and may only be attached to a single controller at a time.
+  and may only be attached to a single controller at a time. Shared namespaces
+  are always automatically attached to all controllers (also when controllers
+  are hotplugged).
 
 ``detached`` (default: ``off``)
   If set to ``on``, the namespace will be be available in the subsystem, but
-  not attached to any controllers initially.
+  not attached to any controllers initially. A shared namespace with this set
+  to ``on`` will never be automatically attached to controllers.
 
 Thus, adding
 
 .. code-block:: console
 
    -drive file=nvm-1.img,if=none,id=nvm-1
-   -device nvme-ns,drive=nvm-1,nsid=1,shared=on
+   -device nvme-ns,drive=nvm-1,nsid=1
    -drive file=nvm-2.img,if=none,id=nvm-2
-   -device nvme-ns,drive=nvm-2,nsid=3,detached=on
+   -device nvme-ns,drive=nvm-2,nsid=3,shared=off,detached=on
 
-will cause NSID 1 will be a shared namespace (due to ``shared=on``) that is
+will cause NSID 1 will be a shared namespace that is initially attached to both
-initially attached to both controllers. NSID 3 will be a private namespace
+controllers. NSID 3 will be a private namespace due to ``shared=off`` and only
-(i.e. only attachable to a single controller at a time) and will not be
+attachable to a single controller at a time. Additionally it will not be
-attached to any controller initially (due to ``detached=on``).
+attached to any controller initially (due to ``detached=on``) or to hotplugged
+controllers.
 
 Optional Features
 =================

hw/core/machine.c

@@ -39,6 +39,7 @@
 
 GlobalProperty hw_compat_6_1[] = {
     { "vhost-user-vsock-device", "seqpacket", "off" },
+    { "nvme-ns", "shared", "off" },
 };
 const size_t hw_compat_6_1_len = G_N_ELEMENTS(hw_compat_6_1);
 

hw/nvme/ns.c

@@ -465,12 +465,6 @@ static void nvme_ns_realize(DeviceState *dev, Error **errp)
                        "linked to an nvme-subsys device");
             return;
         }
-
-        if (ns->params.shared) {
-            error_setg(errp, "shared requires that the nvme device is "
-                       "linked to an nvme-subsys device");
-            return;
-        }
     } else {
         /*
          * If this namespace belongs to a subsystem (through a link on the
@@ -532,7 +526,7 @@ static void nvme_ns_realize(DeviceState *dev, Error **errp)
 static Property nvme_ns_props[] = {
     DEFINE_BLOCK_PROPERTIES(NvmeNamespace, blkconf),
     DEFINE_PROP_BOOL("detached", NvmeNamespace, params.detached, false),
-    DEFINE_PROP_BOOL("shared", NvmeNamespace, params.shared, false),
+    DEFINE_PROP_BOOL("shared", NvmeNamespace, params.shared, true),
     DEFINE_PROP_UINT32("nsid", NvmeNamespace, params.nsid, 0),
     DEFINE_PROP_UUID("uuid", NvmeNamespace, params.uuid),
     DEFINE_PROP_UINT64("eui64", NvmeNamespace, params.eui64, 0),