stos/amd64: mp: Add multiprocessing groundwork

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

paw/stos/arch/amd64/cpu/mp.c

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description:  MP bringup
+ * Author:       Chloe M.
+ */
+
+#include <stdef.h>
+#include <hal/mp.h>
+#include <hal/prim.h>
+#include <ex/trace.h>
+#include <machine/irqchip.h>
+#include <machine/hpet.h>
+#include <machine/lapic.h>
+#include <units.h>
+
+/* Limit used to prevent log spam */
+#define MP_LOG_CAP 4
+#define MP_DEBUG 1
+
+#define DTRACE(Fmt, ...) \
+    TRACE("[ MP ]: " Fmt, ##__VA_ARGS__)
+
+#if MP_DEBUG
+#define MP_DTRACE(...)                  \
+    if (ProcessorsUp < MP_LOG_CAP) {    \
+        DTRACE(__VA_ARGS__);            \
+    }
+#else
+#define MP_DTRACE(...) (VOID)0
+#endif  /* MP_DEBUG */
+
+static USIZE ProcessorsUp = 0;
+
+/*
+ * Bring up a single application processor
+ *
+ * @Lapic: Local APIC of processor to bring up
+ */
+static VOID
+ApKick(ACPI_LOCAL_APIC *Lapic)
+{
+    UQUAD UsecCur, UsecGoal;
+    ULONG BspId;
+
+    if (Lapic == NULL) {
+        return;
+    }
+
+    /* Don't nuke ourselves */
+    BspId = MdLapicId();
+    if (Lapic->ApicId == BspId) {
+        return;
+    }
+
+    /* Send an INIT IPI to the processor */
+    MdLapicSendIpi(
+        0,
+        Lapic->ApicId,
+        0,
+        IPI_XND_NONE,
+        IPI_DELMOD_INIT
+    );
+
+    /* MP spec states to wait 10 usec */
+    UsecCur = MdHpetTimeUsec();
+    UsecGoal = UsecCur + (USEC_PER_MSEC * 10);
+    while (MdHpetTimeUsec() < UsecGoal) {
+        HalCpuSpinWait();
+    }
+
+    DTRACE("sent init to apic%d\n", Lapic->ApicId);
+    ++ProcessorsUp;
+}
+
+VOID
+HalMpBringUp(VOID)
+{
+    ACPI_LOCAL_APIC *LocalApic;
+    USIZE Idx;
+
+    /* Bring up each AP */
+    for (Idx = 0;; ++Idx) {
+        LocalApic = MdLapicByIndex(Idx);
+        if (LocalApic == NULL) {
+            break;
+        }
+
+        ApKick(LocalApic);
+    }
+}

paw/stos/head/hal/mp.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description:  MP bringup HAL layer
+ * Author:       Chloe M.
+ */
+
+#ifndef _HAL_MP_H_
+#define _HAL_MP_H_ 1
+
+#include <stdef.h>
+
+/*
+ * Bring the application processors up
+ */
+VOID HalMpBringUp(VOID);
+
+#endif  /* !_HAL_MP_H_ */

paw/stos/init/init.c

@@ -14,6 +14,7 @@
 #include <hal/serial.h>
 #include <hal/kpcr.h>
 #include <hal/board.h>
+#include <hal/mp.h>
 #include <ob/object.h>
 #include <drivers/bootvid/fbio.h>
 #include <drivers/acpi/acpi.h>
@@ -89,4 +90,7 @@ KiKernelEntry(VOID)
 
     /* Phase 3 initialization of the bootstrap core */
     HalKpcrP3Init(&BootstrapCore);
+
+    /* Bring up all other cores */
+    HalMpBringUp();
 }

tools/qemu-x64.sh

@@ -14,4 +14,5 @@ qemu-system-x86_64            \
     -serial stdio             \
     -device virtio-vga-gl     \
     -display sdl,gl=on        \
+    -smp 4                    \
     -cpu host