stos/amd64: Add Local APIC register defs

Signed-off-by: Chloe M. <chloe@mensia.org>

paw/stos/head/arch/amd64/lapicreg.h

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Local APIC registers
+ * Author:      Chloe M.
+ */
+
+#ifndef _MACHINE_LAPICREG_H_
+#define _MACHINE_LAPICREG_H_ 1
+
+#include <stdef.h>
+
+/* LAPIC register offsets */
+#define LAPIC_ID            0x0020U     /* ID Register */
+#define LAPIC_VERSION       0x0030U     /* Version Register */
+#define LAPIC_TPR           0x0080U     /* Task Priority Register */
+#define LAPIC_APR           0x0090U     /* Arbitration Priority Register */
+#define LAPIC_PPR           0x00A0U     /* Processor Priority Register */
+#define LAPIC_EOI           0x00B0U     /* End Of Interrupt Register */
+#define LAPIC_RRD           0x00C0U     /* Remote Read Register */
+#define LAPIC_LDR           0x00D0U     /* Logical Destination Register */
+#define LAPIC_DFR           0x00E0U     /* Destination Format Register */
+#define LAPIC_SVR           0x00F0U     /* Spurious Vector Register */
+#define LAPIC_ISR           0x0100U     /* In service register (max=0x0220) */
+#define LAPIC_TMR           0x0180U     /* Trigger Mode Register (max=0x0220) */
+#define LAPIC_IRR           0x0200U     /* Interrupt Request Register (max=0x0270) */
+#define LAPIC_ERR           0x0280U     /* Error Status Register */
+#define LAPIC_ICRLO         0x0300U     /* Interrupt Command Low Register */
+#define LAPIC_ICRHI         0x0310U     /* Interrupt Command High Register */
+#define LAPIC_LVT_TMR       0x0320U     /* LVT Timer Register */
+#define LAPIC_DCR           0x03E0U     /* Divide Configuration Register (for timer) */
+#define LAPIC_INIT_CNT      0x0380U     /* Initial Count Register (for timer) */
+#define LAPIC_CUR_CNT       0x0390U     /* Current Count Register (for timer) */
+
+/*
+ * The x2APIC register space is accessed via
+ * RDMSR/WRMSR instructions. The below defines
+ * the base MSR address for the register space.
+ */
+#define x2APIC_MSR_BASE 0x00000800
+
+/*
+ * To hardware enable, OR the value of the IA32_APIC_BASE
+ * MSR with LAPIC_HW_ENABLE and rewrite it.
+ *
+ * To software enable, OR the value of the SVR with
+ * LAPIC_SW_ENABLE and rewrite it.
+ *
+ * LAPIC_SW_ENABLE has the low 8 bits set as some hardware
+ * requires the spurious vector to be hardwired to 1s so
+ * we'll go with that to be safe.
+ */
+#define LAPIC_HW_ENABLE     BIT(11)
+#define LAPIC_SW_ENABLE     (BIT(8) | 0xFF)
+#define x2APIC_ENABLE_SHIFT 10
+
+/* LVT bits */
+#define LAPIC_LVT_MASK            BIT(16)
+#define LVT_TMR_ONESHOT           0x00
+#define LVT_TMR_PERIODIC          0x01
+#define LVT_TMR_TSC_DEADLINE      0x02
+
+#endif  /* !_MACHINE_LAPICREG_H_ */