commit 49c543039050ba85e22f65b719e958a81f4c9c1f
Author: Kostik I. Belousov <kostik@pooma.home>
Date:   Sat Aug 30 21:33:59 2008 +0300

    After reloading %fs, put new fsbase into %r9. This shall allow the
    later code to compare new pcb_fsbase with the actual hw value and
    make a right decision.

diff --git a/sys/amd64/amd64/cpu_switch.S b/sys/amd64/amd64/cpu_switch.S
index f34b0cc..9e13ef4 100644
--- a/sys/amd64/amd64/cpu_switch.S
+++ b/sys/amd64/amd64/cpu_switch.S
@@ -265,6 +265,10 @@ load_seg:
 	movl	PCB_DS(%r8),%ds
 	movl	PCB_ES(%r8),%es
 	movl	PCB_FS(%r8),%fs
+	movl	$MSR_FSBASE,%ecx
+	rdmsr
+	shlq	$32,%rdx
+	leaq	(%rax,%rdx),%r9
 	jmp	done_load_seg
 	/* Restore userland %gs while preserving kernel gsbase */
 2:	movq	PCB_GS32P(%r8),%rax