From f6900b5c3b4832f48359fd761b80f8693a6735e8 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Wed, 16 Jul 2025 20:44:54 -0400
Subject: kernel: Sort out switch MI/MD switch logic

Certain operations dealing with context switches are better off being
implemented as machine dependent routines which allows us to be flexible
with what we can do, as well as the extra benefit of requiring less
workarounds to keep things MI.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/arch/amd64/amd64/lapic_intr.S   |  2 +-
 sys/arch/amd64/amd64/proc_machdep.c | 66 +++++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 1 deletion(-)

(limited to 'sys/arch')

diff --git a/sys/arch/amd64/amd64/lapic_intr.S b/sys/arch/amd64/amd64/lapic_intr.S
index 5ae8f39..1413660 100644
--- a/sys/arch/amd64/amd64/lapic_intr.S
+++ b/sys/arch/amd64/amd64/lapic_intr.S
@@ -33,6 +33,6 @@
     .globl lapic_tmr_isr
 INTRENTRY(lapic_tmr_isr, handle_lapic_tmr)
 handle_lapic_tmr:
-    call sched_switch       // Context switch per every timer IRQ
+    call md_sched_switch    // Context switch per every timer IRQ
     call lapic_eoi          // Done! Signal that we finished to the Local APIC
     retq
diff --git a/sys/arch/amd64/amd64/proc_machdep.c b/sys/arch/amd64/amd64/proc_machdep.c
index 63604a4..72c2b56 100644
--- a/sys/arch/amd64/amd64/proc_machdep.c
+++ b/sys/arch/amd64/amd64/proc_machdep.c
@@ -32,6 +32,8 @@
 #include <sys/param.h>
 #include <sys/errno.h>
 #include <sys/exec.h>
+#include <sys/sched.h>
+#include <sys/schedvar.h>
 #include <machine/frame.h>
 #include <machine/gdt.h>
 #include <machine/cpu.h>
@@ -220,3 +222,67 @@ md_spawn(struct proc *p, struct proc *parent, uintptr_t ip)
     tfp->rsp = ALIGN_DOWN((stack_base + PROC_STACK_SIZE) - 1, 16);
     return 0;
 }
+
+/*
+ * Save thread state and enqueue it back into one
+ * of the ready queues.
+ */
+static void
+sched_save_td(struct proc *td, struct trapframe *tf)
+{
+    /*
+     * Save trapframe to process structure only
+     * if PROC_EXEC is not set.
+     */
+    if (!ISSET(td->flags, PROC_EXEC)) {
+        memcpy(&td->tf, tf, sizeof(td->tf));
+    }
+
+    sched_enqueue_td(td);
+}
+
+static void
+sched_switch_to(struct trapframe *tf, struct proc *td)
+{
+    struct cpu_info *ci;
+    struct pcb *pcbp;
+
+    ci = this_cpu();
+
+    if (tf != NULL) {
+        memcpy(tf, &td->tf, sizeof(*tf));
+    }
+
+    ci->curtd = td;
+    pcbp = &td->pcb;
+    pmap_switch_vas(pcbp->addrsp);
+}
+
+/*
+ * Perform a context switch.
+ */
+void
+md_sched_switch(struct trapframe *tf)
+{
+    struct proc *next_td, *td;
+    struct cpu_info *ci;
+
+    ci = this_cpu();
+    td = ci->curtd;
+    mi_sched_switch(td);
+
+    if (td != NULL) {
+        if (td->pid == 0)
+            return;
+
+        sched_save_td(td, tf);
+    }
+
+    if ((next_td = sched_dequeue_td()) == NULL) {
+        sched_oneshot(false);
+        return;
+    }
+
+    sched_switch_to(tf, next_td);
+    sched_oneshot(false);
+}
-- 
cgit v1.2.3