OS-7125 Need mitigation of L1TF (CVE-2018-3646)
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>

@@ -21,10 +21,11 @@
 
 /*
  * Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012 by Delphix. All rights reserved.
  * Copyright 2014 Igor Kozhukhov <ikozhukhov@gmail.com>.
+ * Copyright 2018 Joyent, Inc.
  * Copyright 2017 RackTop Systems.
  */
 
 #ifndef _SYS_CPUVAR_H
 #define _SYS_CPUVAR_H

@@ -570,17 +571,23 @@
 #else
 #define CPU             (curthread->t_cpu)      /* Pointer to current CPU */
 #endif
 
 /*
- * CPU_CURRENT indicates to thread_affinity_set to use CPU->cpu_id
- * as the target and to grab cpu_lock instead of requiring the caller
- * to grab it.
+ * CPU_CURRENT indicates to thread_affinity_set() to use whatever curthread's
+ * current CPU is; holding cpu_lock is not required.
  */
 #define CPU_CURRENT     -3
 
 /*
+ * CPU_BEST can be used by thread_affinity_set() callers to set affinity to a
+ * good CPU (in particular, an ht_acquire()-friendly choice); holding cpu_lock
+ * is not required.
+ */
+#define CPU_BEST        -4
+
+/*
  * Per-CPU statistics
  *
  * cpu_stats_t contains numerous system and VM-related statistics, in the form
  * of gauges or monotonically-increasing event occurrence counts.
  */