Update OSDK guide

docs/src/osdk/guide/work-in-workspace.md

@@ -1 +1,100 @@
 # Working in a Workspace
+
+Typically, an operating system may consist of multiple crates, and these crates may be organized in a workspace. OSDK also supports managing projects in a workspace. Below is an example that demonstrates how to create, build, run, and test projects in a workspace.
+
+## Creating a new workspace
+
+Create a new workspace by executing the following commands:
+
+```bash
+mkdir myworkspace && cd myworkspace
+touch Cargo.toml
+```
+
+Then, add the following content to `Cargo.toml`:
+
+```toml
+[workspace]
+members = []
+resolver = "2"
+```
+
+## Creating a kernel project and a library project
+
+The two projects can be created using the following commands:
+
+```bash
+cargo osdk new --kernel myos
+cargo osdk new mymodule
+```
+
+The generated directory structure will be as follows:
+
+```text
+myworkspace/
+  Cargo.toml
+  OSDK.toml
+  rust-toolchain.toml
+  myos/
+    src/
+      lib.rs
+    Cargo.toml
+  mymodule/
+    src/    
+      lib.rs
+    Cargo.toml
+```
+
+In addition to the two projects, OSDK will also generate `OSDK.toml` and `rust-toolchain.toml` at the root of the workspace.
+
+Next, add the following function to `mymodule/src/lib.rs`. This function will calculate the available memory after booting:
+
+```rust
+pub fn available_memory() -> usize {
+    let regions = aster_frame::boot::memory_regions();
+    regions.iter().map(|region| region.len()).sum()
+}
+```
+
+Then, add a dependency on `mymodule` to `myos/Cargo.toml`:
+
+```toml
+[dependencies]
+mymodule = { path = "../mymodule" }
+```
+
+In `myos/src/lib.rs`, modify the main function as follows. This function will call the function from `mymodule`:
+
+```rust
+#[aster_main]
+fn kernel_main() -> ! {
+  let avail_mem_as_mb = mymodule::available_memory() / 0x1_000_000;
+  println!("The available memory is {} MB", avail_mem_as_mb);
+  abort();
+}
+```
+
+## Building and Running the kernel
+
+Build and run the project using the following commands:
+
+```bash
+cargo osdk build
+cargo osdk run
+```
+
+If everything goes well, you will see the output from the guest kernel.
+
+## Running unit test
+
+You can run test cases from all crates by using the following command in the workspace folder:
+
+```bash
+cargo osdk test
+```
+
+If you want to run test cases from a specific crate, navigate to the crate's folder and run `cargo osdk test`. For example, if you want to test `myos`, use the following command: 
+
+```bash
+cd myos && cargo osdk test
+```