Handout

kernel/arch/ioapic.cc

@@ -0,0 +1,123 @@
+#include "ioapic.h"
+
+#include "../debug/assert.h"
+#include "apic.h"
+#include "core.h"
+
+namespace IOAPIC {
+/*! \brief IOAPIC registers memory mapped into the CPU's address space.
+ *
+ *  Access to the actual IOAPIC registers can be obtained by performing the
+ * following steps:
+ *  1. Write the number of the IOAPIC register to the address stored in
+ * `IOREGSEL_REG`
+ *  2. Read the value from / write the value to the address referred to by
+ * `IOWIN_REG`.
+ *
+ *  \see [IO-APIC manual](intel_ioapic.pdf#page=8)
+ */
+volatile Index *IOREGSEL_REG = reinterpret_cast<volatile Index *>(0xfec00000);
+/// \copydoc IOREGSEL_REG
+volatile Register *IOWIN_REG =
+	reinterpret_cast<volatile Register *>(0xfec00010);
+
+// IOAPIC manual, p. 8
+const Index IOAPICID_IDX = 0x00;
+const Index IOREDTBL_IDX = 0x10;
+
+const uint8_t slot_max = 24;
+
+// Helper function that reads a single register
+static Register read(Index reg) {
+	*IOREGSEL_REG = reg;
+	Register value = *IOWIN_REG;
+	return value;
+}
+
+// Helper function that writes a single register
+static void write(Index reg, Register value) {
+	*IOREGSEL_REG = reg;
+	*IOWIN_REG = value;
+}
+
+// Helper function that reads an entry (= reads from TWO registers) from the
+// redirection table
+static RedirectionTableEntry getRedirectionTableEntry(uint8_t slot) {
+	assert(slot < slot_max);
+	return RedirectionTableEntry(read(IOREDTBL_IDX + 2 * slot + 0),
+								 read(IOREDTBL_IDX + 2 * slot + 1));
+}
+// Helper function that writes an entry (= writes to TWO registers) to the
+// redirection table
+static void setRedirectionTableEntry(uint8_t slot, RedirectionTableEntry rt) {
+	assert(slot < slot_max);
+	write(IOREDTBL_IDX + 2 * slot + 0, rt.value_low);
+	write(IOREDTBL_IDX + 2 * slot + 1, rt.value_high);
+}
+
+static void setID(uint8_t id) {
+	Identification reg(read(IOAPICID_IDX));
+	reg.id = id;
+	write(IOAPICID_IDX, reg.value);
+}
+
+void init() {
+	// optional:
+	IOREGSEL_REG = reinterpret_cast<volatile Index *>(APIC::getIOAPICAddress());
+	IOWIN_REG =
+		reinterpret_cast<volatile Index *>(APIC::getIOAPICAddress() + 0x10);
+
+	// set 4-bit ID to correct IO-APIC value, determined at startup
+	setID(APIC::getIOAPICID());
+
+	for (uint8_t i = 0; i < slot_max; ++i) {
+		RedirectionTableEntry rt = getRedirectionTableEntry(i);
+
+		/* The old solution used 0xff as `destination` here, but the Intel
+		 * manual (3A, 10.6.2.2 - Logical Destination Mode) states the
+		 * following: "For both configurations of logical destination mode, when
+		 * combined with lowest priority delivery mode, software is responsible
+		 * for ensuring that all of the local APICs included in or addressed by
+		 * the IPI or I/O subsystem interrupt are present and enabled to receive
+		 * the interrupt." More recent processors assume the correctness of the
+		 * value written to `destination`, and, therefore, will try to redirect
+		 * the interrupt to non-existing LAPIC if misconfigured and wait for
+		 * response.
+		 */
+		rt.destination = 1;
+		rt.vector = static_cast<uint8_t>(Core::Interrupt::Vector::PANIC);
+		rt.delivery_mode = DeliveryMode::LOWEST_PRIORITY;
+		rt.destination_mode = DestinationMode::LOGICAL;
+		rt.polarity = Polarity::HIGH;
+		rt.trigger_mode = TriggerMode::EDGE;
+		rt.interrupt_mask = InterruptMask::MASKED;
+		setRedirectionTableEntry(i, rt);
+	}
+}
+
+void config(uint8_t slot, Core::Interrupt::Vector vector,
+			TriggerMode trigger_mode, Polarity polarity) {
+	RedirectionTableEntry rt = getRedirectionTableEntry(slot);
+	rt.vector = static_cast<uint8_t>(vector);
+	rt.polarity = polarity;
+	rt.trigger_mode = trigger_mode;
+	setRedirectionTableEntry(slot, rt);
+}
+
+void allow(uint8_t slot) {
+	RedirectionTableEntry rt = getRedirectionTableEntry(slot);
+	rt.interrupt_mask = InterruptMask::UNMASKED;
+	setRedirectionTableEntry(slot, rt);
+}
+
+void forbid(uint8_t slot) {
+	RedirectionTableEntry rt = getRedirectionTableEntry(slot);
+	rt.interrupt_mask = InterruptMask::MASKED;
+	setRedirectionTableEntry(slot, rt);
+}
+
+bool status(uint8_t slot) {
+	RedirectionTableEntry rt = getRedirectionTableEntry(slot);
+	return rt.interrupt_mask == InterruptMask::UNMASKED;
+}
+}  // namespace IOAPIC