9p: change the default securityModel from mapped-xattr to none

The `mapped-xattr` model is known to be incompatible with symlinks:
https://gitlab.com/qemu-project/qemu/-/issues/173

The `none` model is obviously incompatible with chown, but this is
fine, as the reverse-sshfs does not support chown either.

See issue 971

Signed-off-by: Akihiro Suda <[email protected]>

Author: AkihiroSuda

docs/mount.md

@@ -59,7 +59,8 @@ mounts:
 - location: "~"
   9p:
     # Supported security models are "passthrough", "mapped-xattr", "mapped-file" and "none".
-    # 🟢 Builtin default: "mapped-xattr"
+    # "mapped-xattr" and "mapped-file" are useful for persistent chown but incompatible with symlinks.
+    # 🟢 Builtin default: "none" (since Lima v0.13)
     securityModel: null
     # Select 9P protocol version. Valid options are: "9p2000" (legacy), "9p2000.u", "9p2000.L".
     # 🟢 Builtin default: "9p2000.L"

examples/default.yaml

@@ -69,7 +69,8 @@ mounts:
     sftpDriver: null
   9p:
     # Supported security models are "passthrough", "mapped-xattr", "mapped-file" and "none".
-    # 🟢 Builtin default: "mapped-xattr"
+    # "mapped-xattr" and "mapped-file" are useful for persistent chown but incompatible with symlinks.
+    # 🟢 Builtin default: "none" (since Lima v0.13)
     securityModel: null
     # Select 9P protocol version. Valid options are: "9p2000" (legacy), "9p2000.u", "9p2000.L".
     # 🟢 Builtin default: "9p2000.L"

pkg/limayaml/defaults.go

@@ -20,7 +20,9 @@ import (
 )
 
 const (
-	Default9pSecurityModel   string = "mapped-xattr"
+	// Default9pSecurityModel is "none" for supporting symlinks
+	// https://gitlab.com/qemu-project/qemu/-/issues/173
+	Default9pSecurityModel   string = "none"
 	Default9pProtocolVersion string = "9p2000.L"
 	Default9pMsize           string = "128KiB"
 	Default9pCacheForRO      string = "fscache"