feat(pl/ke): initial amd64 support

src/platform/amd64/impl.zig

@@ -1,6 +1,25 @@
-const entry = @import("entry.zig");
+const b = @import("base");
+const ki = b.ke.private;
 
-pub const first_init = entry.first_init;
+pub const name = "AMD64";
+
+pub fn first_init() void {}
+
+pub fn early_init() void {
+    const impl_cpu = &ki.bootstrap_cpu.impl;
+    impl_cpu.self_ptr = impl_cpu;
+    impl_cpu.percpu_offset = 0;
+
+    const impl_cpu_ptr = @intFromPtr(impl_cpu);
+    asm volatile ("wrmsr"
+        :
+        : [_] "{eax}" (@as(u32, @intCast(impl_cpu_ptr & 0xFFFFFFFF))),
+          [_] "{edx}" (@as(u32, @truncate(impl_cpu_ptr >> 32))),
+          [_] "{ecx}" (0xC000_0101),
+    );
+}
+
+pub fn late_init() void {}
 
 pub fn devices_init() void {}