[src/trunk]: src/sys/arch/x86/x86 If the CPU is not vulnerable to SpectreV4, ...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3b07821eac7d
branches:  trunk
changeset: 446842:3b07821eac7d
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Dec 22 08:59:44 2018 +0000

description:
If the CPU is not vulnerable to SpectreV4, say it in the sysctl by default.
Apply some minor style while here.

diffstat:

 sys/arch/x86/x86/spectre.c |  22 ++++++++++++++++++----
 1 files changed, 18 insertions(+), 4 deletions(-)

diffs (59 lines):

diff -r b80db9b93fcf -r 3b07821eac7d sys/arch/x86/x86/spectre.c
--- a/sys/arch/x86/x86/spectre.c        Sat Dec 22 08:35:04 2018 +0000
+++ b/sys/arch/x86/x86/spectre.c        Sat Dec 22 08:59:44 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: spectre.c,v 1.19 2018/05/28 20:18:58 maxv Exp $        */
+/*     $NetBSD: spectre.c,v 1.20 2018/12/22 08:59:44 maxv Exp $        */
 
 /*
  * Copyright (c) 2018 NetBSD Foundation, Inc.
@@ -34,7 +34,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: spectre.c,v 1.19 2018/05/28 20:18:58 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: spectre.c,v 1.20 2018/12/22 08:59:44 maxv Exp $");
 
 #include "opt_spectre.h"
 
@@ -483,7 +483,8 @@
        mitigation_v4_apply_cpu(enabled);
 }
 
-static int mitigation_v4_change(bool enabled)
+static int
+mitigation_v4_change(bool enabled)
 {
        struct cpu_info *ci = NULL;
        CPU_INFO_ITERATOR cii;
@@ -609,6 +610,10 @@
         *
         * cpu0 is the one that detects the method and sets the global
         * variable.
+        *
+        * Disabled by default, as recommended by AMD, but can be enabled
+        * dynamically. We only detect if the CPU is not vulnerable, to
+        * mark it as 'mitigated' in the sysctl.
         */
 #if 0
        if (ci == &cpu_info_primary) {
@@ -617,9 +622,18 @@
                    (v4_mitigation_method != V4_MITIGATION_NONE);
                v4_set_name();
        }
-       if (v4_mitigation_method != V4_MITIGATION_NONE) {
+       if (v4_mitigation_method != V4_MITIGATION_NONE &&
+           v4_mitigation_method != V4_MITIGATION_INTEL_SSB_NO) {
                mitigation_v4_apply_cpu(ci, true);
        }
+#else
+       if (ci == &cpu_info_primary) {
+               v4_detect_method();
+               if (v4_mitigation_method == V4_MITIGATION_INTEL_SSB_NO) {
+                       v4_mitigation_enabled = true;
+                       v4_set_name();
+               }
+       }
 #endif
 }