kern/amd64: Add I/O APIC initialization code

This commit introduces the initial I/O APIC driver code that does basic
initialization i.e., grabbing base address from MADT, masking each pin,
etc.

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 107 insertions, 0 deletions

diff --git a/src/sys/include/arch/amd64/ioapic.h b/src/sys/include/arch/amd64/ioapic.h
new file mode 100644
index 0000000..9cd8bd4
--- /dev/null
+++ b/src/sys/include/arch/amd64/ioapic.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the project nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _MACHINE_IOAPIC_H_
+#define _MACHINE_IOAPIC_H_ 1
+
+/* Mask arguments for ioapic_gsi_mask() */
+#define IOAPIC_PIN_MASK     1
+#define IOAPIC_PIN_UNMASK   0
+
+/*
+ * Initialize the I/O APIC into a basic state,
+ * all interrupts will be masked.
+ */
+void ioapic_init(void);
+
+/*
+ * Mask or unmask a global system interrupt by index
+ *
+ * @gsi: Global system interrupt to mask
+ * @mask: 1->masked,0->unmasked
+ */
+void ioapic_gsi_mask(uint8_t gsi, uint8_t mask);
+
+#endif  /* !_MACHINE_IOAPIC_H_ */
diff --git a/src/sys/include/arch/amd64/ioapicvar.h b/src/sys/include/arch/amd64/ioapicvar.h
new file mode 100644
index 0000000..eb4fab5
--- /dev/null
+++ b/src/sys/include/arch/amd64/ioapicvar.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the project nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _IOAPICVAR_H_
+#define _IOAPIC_VAR_H_ 1
+
+/* Register offsets */
+#define IOREGSEL    0x00
+#define IOWIN       0x10
+#define IOREDTBL    0x10
+#define IOAPICID    0x00
+#define IOAPICVER   0x01
+
+union ioapic_redentry {
+    struct {
+        uint8_t vector;
+        uint8_t delmod          : 3;
+        uint8_t destmod         : 1;
+        uint8_t delivs          : 1;
+        uint8_t intpol          : 1;
+        uint8_t remote_irr      : 1;
+        uint8_t trigger_mode    : 1;
+        uint8_t interrupt_mask  : 1;
+        uint64_t reserved       : 39;
+        uint8_t dest_field;
+    };
+    uint64_t value;
+};
+
+#endif  /* !_IOAPIC_VAR_H_ */