From 05eb70e9f06c4030c7122fefb714300e57f5868a Mon Sep 17 00:00:00 2001
From: mintsuki <mintsuki@protonmail.com>
Date: Mon, 13 Sep 2021 05:13:02 +0200
Subject: [PATCH] smp: Use rdtsc to delay rather than dummy port IO

---
 stage23/sys/smp.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/stage23/sys/smp.c b/stage23/sys/smp.c
index 79f463e9..14c3d777 100644
--- a/stage23/sys/smp.c
+++ b/stage23/sys/smp.c
@@ -39,9 +39,10 @@ struct madt_x2apic {
     uint32_t acpi_processor_uid;
 } __attribute__((packed));
 
-static void delay(uint32_t cycles) {
-    for (uint32_t i = 0; i < cycles; i++)
-        inb(0x80);
+static void delay(uint64_t cycles) {
+    uint64_t next_stop = rdtsc() + cycles;
+
+    while (rdtsc() < next_stop);
 }
 
 extern symbol _binary_smp_trampoline_bin_start;
@@ -95,7 +96,7 @@ static bool smp_start_ap(uint32_t lapic_id, struct gdtr *gdtr,
         lapic_write(LAPIC_REG_ICR1, lapic_id << 24);
         lapic_write(LAPIC_REG_ICR0, 0x4500);
     }
-    delay(5000);
+    delay(10000000);
 
     // Send the Startup IPI
     if (x2apic) {
@@ -110,7 +111,7 @@ static bool smp_start_ap(uint32_t lapic_id, struct gdtr *gdtr,
         if (locked_read(&passed_info->smp_tpl_booted_flag) == 1) {
             return true;
         }
-        delay(10000);
+        delay(10000000);
     }
 
     return false;