WIP x86 smp: start the framework for detecting and starting secondary cores

platform/pc/mp.c

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2024 Travis Geiselbrecht
+ *
+ * Use of this source code is governed by a MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "platform_p.h"
+
+#include <lk/main.h>
+#include <lib/acpi_lite.h>
+#include <lk/trace.h>
+
+#define LOCAL_TRACE 1
+
+static void start_cpu(uint cpu_num, uint32_t apic_id) {
+    LTRACEF("cpu_num %u, apic_id %u\n", cpu_num, apic_id);
+
+    // XXX do work here
+}
+
+struct detected_cpus {
+    uint32_t num_detected;
+    uint32_t apic_ids[SMP_MAX_CPUS];
+};
+
+static void local_apic_callback(const void *_entry, size_t entry_len, void *cookie) {
+    const struct acpi_madt_local_apic_entry *entry = _entry;
+    struct detected_cpus *cpus = cookie;
+
+    if (entry->apic_id == 0) {
+        // skip the boot cpu
+        return;
+    }
+    if (cpus->num_detected < SMP_MAX_CPUS) {
+        cpus->apic_ids[cpus->num_detected++] = entry->apic_id;
+    }
+}
+
+void platform_start_secondary_cpus(void) {
+    struct detected_cpus cpus;
+    cpus.num_detected = 1;
+    cpus.apic_ids[0] = 0; // the boot cpu
+
+    acpi_process_madt_entries_etc(ACPI_MADT_TYPE_LOCAL_APIC, &local_apic_callback, &cpus);
+
+    // TODO: fall back to legacy methods if ACPI fails
+    // TODO: deal with cpu topology
+
+    // start up the secondary cpus
+    if (cpus.num_detected > 1) {
+        dprintf(INFO, "PC: detected %u cpus\n", cpus.num_detected);
+
+        lk_init_secondary_cpus(cpus.num_detected - 1);
+
+        for (uint i = 1; i < cpus.num_detected; i++) {
+            dprintf(INFO, "PC: starting cpu %u\n", cpus.apic_ids[i]);
+            start_cpu(i, cpus.apic_ids[i]);
+        }
+    }
+}
+