From dda84ba927c42ed227ce93ed2a0f0d16058bb2c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Florian=20N=C3=BCcke?= <florian@nuecke.de>
Date: Thu, 24 Sep 2020 16:54:32 +0200
Subject: [PATCH] Added bare minimum VirtIO console device.

---
 .../vm/device/virtio/VirtIOConsoleDevice.java | 133 ++++++++++++++++++
 1 file changed, 133 insertions(+)
 create mode 100644 src/main/java/li/cil/circuity/vm/device/virtio/VirtIOConsoleDevice.java

diff --git a/src/main/java/li/cil/circuity/vm/device/virtio/VirtIOConsoleDevice.java b/src/main/java/li/cil/circuity/vm/device/virtio/VirtIOConsoleDevice.java
new file mode 100644
index 00000000..08da1db3
--- /dev/null
+++ b/src/main/java/li/cil/circuity/vm/device/virtio/VirtIOConsoleDevice.java
@@ -0,0 +1,133 @@
+package li.cil.circuity.vm.device.virtio;
+
+import li.cil.circuity.api.vm.MemoryMap;
+import li.cil.circuity.api.vm.device.memory.MemoryAccessException;
+
+@SuppressWarnings("PointlessBitwiseExpression")
+public final class VirtIOConsoleDevice extends AbstractVirtIODevice {
+    private static final short DEFAULT_COLUMN_COUNT = 80;
+    private static final short DEFAULT_ROW_COUNT = 25;
+
+    private static final long VIRTIO_CONSOLE_F_SIZE = 1L << 0; // Configuration for cols and rows.
+    private static final long VIRTIO_CONSOLE_F_MULTIPORT = 1L << 1; // Configuration max_nr_ports, control virtqueues.
+    private static final long VIRTIO_CONSOLE_F_EMERG_WRITE = 1L << 2; // Supports emergency write.
+
+    private static final int VIRTIO_CONSOLE_DEVICE_READY = 0;
+    private static final int VIRTIO_CONSOLE_DEVICE_ADD = 1;
+    private static final int VIRTIO_CONSOLE_DEVICE_REMOVE = 2;
+    private static final int VIRTIO_CONSOLE_PORT_READY = 3;
+    private static final int VIRTIO_CONSOLE_CONSOLE_PORT = 4;
+    private static final int VIRTIO_CONSOLE_RESIZE = 5;
+    private static final int VIRTIO_CONSOLE_PORT_OPEN = 6;
+    private static final int VIRTIO_CONSOLE_PORT_NAME = 7;
+
+    private static final int VIRTIO_CONSOLE_CFG_COLS_OFFSET = 0;
+    private static final int VIRTIO_CONSOLE_CFG_ROWS_OFFSET = 2;
+    private static final int VIRTIO_CONSOLE_CFG_MAX_NR_PORTS_OFFSET = 4;
+    private static final int VIRTIO_CONSOLE_CFG_EMERG_WR_OFFSET = 8;
+
+    private static final int VIRTQ_RECEIVE = 0; // receiveq(port0)
+    private static final int VIRTQ_TRANSMIT = 1; // transmitq(port0)
+    private static final int VIRTQ_RECEIVE_CONTROL = 2; // control receiveq
+    private static final int VIRTQ_TRANSMIT_CONTROL = 2; // control transmitq
+
+    private DescriptorChain receive, transmit;
+
+    public VirtIOConsoleDevice(final MemoryMap memoryMap) {
+        super(memoryMap, VirtIODeviceSpec
+                .builder(VirtIODeviceType.VIRTIO_DEVICE_ID_CONSOLE)
+                .features(VIRTIO_CONSOLE_F_SIZE)
+                .queueCount(2)
+                .configSpaceSize(4)
+                .build());
+    }
+
+    public int read() {
+        if (hasDeviceFailed()) {
+            return -1;
+        }
+
+        try {
+            // 5.3.6.1: The driver MUST NOT put a device-writable buffer in a transmitq.
+            transmit = validateReadOnlyDescriptorChain(VIRTQ_TRANSMIT, transmit);
+            if (transmit != null) {
+                return transmit.get() & 0xFF;
+            } else {
+                return -1;
+            }
+        } catch (final VirtIODeviceException | MemoryAccessException e) {
+            error();
+            return -1;
+        }
+    }
+
+    public boolean canPutByte() {
+        if (hasDeviceFailed()) {
+            return false;
+        }
+
+        try {
+            // 5.3.6.1: The driver MUST NOT put a device-readable in a receiveq.
+            receive = validateWriteOnlyDescriptorChain(VIRTQ_RECEIVE, receive);
+            return receive != null;
+        } catch (final VirtIODeviceException | MemoryAccessException e) {
+            error();
+            return false;
+        }
+    }
+
+    public void putByte(final byte value) {
+        if (hasDeviceFailed()) {
+            return;
+        }
+
+        try {
+            // 5.3.6.1: The driver MUST NOT put a device-readable in a receiveq.
+            receive = validateWriteOnlyDescriptorChain(VIRTQ_RECEIVE, receive);
+            if (receive != null) {
+                receive.put(value);
+            }
+        } catch (final VirtIODeviceException | MemoryAccessException e) {
+            error();
+        }
+    }
+
+    public void flush() {
+        if (hasDeviceFailed()) {
+            return;
+        }
+
+        try {
+            // 5.3.6.1: The driver MUST NOT put a device-readable in a receiveq.
+            receive = validateWriteOnlyDescriptorChain(VIRTQ_RECEIVE, receive);
+            if (receive != null) {
+                receive.use();
+            }
+        } catch (final VirtIODeviceException | MemoryAccessException e) {
+            error();
+        }
+    }
+
+    @Override
+    protected void initializeConfig() {
+        setConfigValue(VIRTIO_CONSOLE_CFG_COLS_OFFSET, DEFAULT_COLUMN_COUNT);
+        setConfigValue(VIRTIO_CONSOLE_CFG_ROWS_OFFSET, DEFAULT_ROW_COUNT);
+    }
+
+    @Override
+    protected void storeConfig(final int offset, final int value, final int sizeLog2) {
+        if (offset == VIRTIO_CONSOLE_CFG_EMERG_WR_OFFSET) {
+            // 5.3.5.1: The device SHOULD transmit the lower byte written to emerg_wr [...]
+        }
+    }
+
+    @Override
+    protected void handleFeaturesNegotiated() {
+        setQueueNotifications(VIRTQ_RECEIVE, false);
+        setQueueNotifications(VIRTQ_TRANSMIT, false);
+    }
+
+    private boolean hasDeviceFailed() {
+        return (getStatus() & VIRTIO_STATUS_FAILED) != 0;
+    }
+}