kernel: fix test-in-svsm use of the test serial port

The test serial port must use the same platform abstraction as the rest
of the I/O port abstraction.  Since serial port construction is now
platform-specific, the construction is moved to the first use of the
test serial port.  The serial port cell is changed to an `Option` to
simplify the synchronization of the dynamic initialization across
consumers.

Also, for better abstraction, the operation to obtain the test serial
port doesn't emit a byte; it simply returns the port so the caller can
write whatever it wants.

Signed-off-by: Jon Lange <[email protected]>

kernel/src/greq/services.rs

@@ -121,7 +121,9 @@ mod tests {
 
         use alloc::vec;
 
-        let sp = svsm_test_io(IORequest::GetLaunchMeasurement);
+        let sp = svsm_test_io().unwrap();
+
+        sp.put_byte(IORequest::GetLaunchMeasurement as u8);
 
         let mut expected_measurement = [0u8; 48];
         for byte in &mut expected_measurement {

kernel/src/testing.rs

@@ -4,13 +4,11 @@ use test::ShouldPanic;
 use crate::{
     cpu::percpu::current_ghcb,
     locking::{LockGuard, SpinLock},
-    serial::{SerialPort, Terminal},
+    platform::SVSM_PLATFORM,
+    serial::SerialPort,
     sev::ghcb::GHCBIOSize,
-    svsm_console::SVSMIOPort,
 };
 
-use core::sync::atomic::{AtomicBool, Ordering};
-
 #[macro_export]
 macro_rules! assert_eq_warn {
     ($left:expr, $right:expr) => {
@@ -30,10 +28,7 @@ macro_rules! assert_eq_warn {
 }
 pub use assert_eq_warn;
 
-static SERIAL_INITIALIZED: AtomicBool = AtomicBool::new(false);
-static IOPORT: SVSMIOPort = SVSMIOPort::new();
-static SERIAL_PORT: SpinLock<SerialPort<'_>> =
-    SpinLock::new(SerialPort::new(&IOPORT, 0x2e8 /*COM4*/));
+static SERIAL_PORT: SpinLock<Option<SerialPort<'_>>> = SpinLock::new(None);
 
 /// Byte used to tell the host the request we need for the test.
 /// These values must be aligned with `test_io()` in scripts/test-in-svsm.sh
@@ -49,17 +44,15 @@ pub enum IORequest {
 /// used in a test. The request (first byte) is sent by this function, so the
 /// caller can start using the serial port according to the request implemented
 /// in `test_io()` in scripts/test-in-svsm.sh
-pub fn svsm_test_io(req: IORequest) -> LockGuard<'static, SerialPort<'static>> {
-    let sp = SERIAL_PORT.lock();
-    if SERIAL_INITIALIZED
-        .compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
-        .is_ok()
-    {
-        sp.init();
+pub fn svsm_test_io() -> LockGuard<'static, Option<SerialPort<'static>>> {
+    let mut sp = SERIAL_PORT.lock();
+    if sp.is_none() {
+        let io_port = SVSM_PLATFORM.as_dyn_ref().get_io_port();
+        let serial_port = SerialPort::new(io_port, 0x2e8 /*COM4*/);
+        *sp = Some(serial_port);
+        serial_port.init();
     }
 
-    sp.put_byte(req as u8);
-
     sp
 }