virtio-fs: make permission semantics configurable

docs/usage.md

@@ -215,6 +215,7 @@ the arguments.
 
 - `sharedDir`: Path to the host directory that will be shared with the guest.
 - `mountTag`: Tag to be used to mount the shared directory in the guest.
+- `permissionSemantics`: (Optional) Permission semantics to be used in the virtio-fs device. Supported values: `complete`, `simplified`. Default value is `simplified`.
 
 #### Example
 
@@ -224,6 +225,12 @@ This will share `/Users/user/shared-dir` with the guest:
 --device virtio-fs,sharedDir=/Users/user/shared-dir,mountTag=MOUNT_TAG
 ```
 
+To use complete permission semantics:
+
+```
+--device virtio-fs,sharedDir=/Users/user/shared-dir,mountTag=MOUNT_TAG,permissionSemantics=complete
+```
+
 ## Restful Service
 
 Recall that the RESTful service is started at the address specified in the `--restful-uri` argument (or

src/virtio.rs

@@ -52,7 +52,14 @@ extern "C" {
     ) -> i32;
     fn krun_add_vsock_port2(ctx_id: u32, port: u32, c_filepath: *const c_char, listen: bool)
         -> i32;
-    fn krun_add_virtiofs(ctx_id: u32, c_tag: *const c_char, c_path: *const c_char) -> i32;
+    fn krun_add_virtiofs4(
+        ctx_id: u32,
+        c_tag: *const c_char,
+        c_path: *const c_char,
+        shm_size: u64,
+        read_only: bool,
+        semantics: u32,
+    ) -> i32;
     fn krun_set_console_output(ctx_id: u32, c_filepath: *const c_char) -> i32;
     fn krun_add_net_unixgram(
         ctx_id: u32,
@@ -92,6 +99,25 @@ impl FromStr for DiskImageFormat {
     }
 }
 
+#[derive(Clone, Debug, Default, PartialEq)]
+pub enum FsPermissions {
+    Complete = 0,
+    #[default]
+    Simplified = 1,
+}
+
+impl FromStr for FsPermissions {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.to_lowercase().as_str() {
+            "complete" => Ok(FsPermissions::Complete),
+            "simplified" => Ok(FsPermissions::Simplified),
+            _ => Err(anyhow!("unsupported permission semantics")),
+        }
+    }
+}
+
 /// Each virito device configures itself with krun differently. This is used by each virtio device
 /// to set their respective configurations with libkrun.
 pub trait KrunContextSet {
@@ -584,6 +610,8 @@ pub struct FsConfig {
 
     /// Guest mount tag for shared directory.
     pub mount_tag: PathBuf,
+
+    pub permission_semantics: FsPermissions,
 }
 
 impl FromStr for FsConfig {
@@ -602,6 +630,10 @@ impl FromStr for FsConfig {
         fs_config.mount_tag =
             PathBuf::from_str(mount_tag.as_str()).context("mountTag argument not a valid path")?;
 
+        if let Some(p) = args.remove("permissionSemantics") {
+            fs_config.permission_semantics = FsPermissions::from_str(p.as_str())?;
+        }
+
         check_unknown_args(args, "virtio-fs")?;
 
         Ok(fs_config)
@@ -614,7 +646,15 @@ impl KrunContextSet for FsConfig {
         let shared_dir_cstr = path_to_cstring(&self.shared_dir)?;
         let mount_tag_cstr = path_to_cstring(&self.mount_tag)?;
 
-        if krun_add_virtiofs(id, mount_tag_cstr.as_ptr(), shared_dir_cstr.as_ptr()) < 0 {
+        if krun_add_virtiofs4(
+            id,
+            mount_tag_cstr.as_ptr(),
+            shared_dir_cstr.as_ptr(),
+            0,
+            false,
+            self.permission_semantics.clone() as u32,
+        ) < 0
+        {
             return Err(anyhow!(format!(
                 "unable to add virtiofs shared directory {} with mount tag {}",
                 &self.shared_dir.display(),