Index: src/sys/amd64/amd64/mp_machdep.c
===================================================================
RCS file: /home/ncvs/src/sys/amd64/amd64/mp_machdep.c,v
retrieving revision 1.287.2.2
diff -u -p -u -r1.287.2.2 mp_machdep.c
--- src/sys/amd64/amd64/mp_machdep.c	28 Nov 2007 23:24:06 -0000	1.287.2.2
+++ src/sys/amd64/amd64/mp_machdep.c	18 May 2008 13:45:32 -0000
@@ -457,10 +457,18 @@ init_secondary(void)
 	common_tss[cpu].tss_iobase = sizeof(struct amd64tss);
 	common_tss[cpu].tss_ist1 = (long)&doublefault_stack[PAGE_SIZE];
 
+	/* Use a seperate gdt for each cpu because the tss differs.
+	 * This avoids complications for e.g. virtualization software
+	 * that needs to reload the task register and otherwise would
+	 * then end up using the last cpu's tss on others.
+	 */
+	bcopy(gdt, &gdt[NGDT * cpu], NGDT * sizeof(gdt[0]));
+
 	gdt_segs[GPROC0_SEL].ssd_base = (long) &common_tss[cpu];
 	ssdtosyssd(&gdt_segs[GPROC0_SEL],
-	   (struct system_segment_descriptor *)&gdt[GPROC0_SEL]);
+	   (struct system_segment_descriptor *)&gdt[NGDT * cpu + GPROC0_SEL]);
 
+	r_gdt.rd_base =  (long) &gdt[NGDT * cpu];
 	lgdt(&r_gdt);			/* does magic intra-segment return */
 
 	/* Get per-cpu data */