releases/5.0.16/0021-x86-speculation-Support-mitigations-cmdline-option.patch

   1 From 1aaa69ec96c73918d45177d9d35680f648d0faed Mon Sep 17 00:00:00 2001
   2 From: Josh Poimboeuf <jpoimboe@redhat.com>
   3 Date: Fri, 12 Apr 2019 15:39:29 -0500
   4 Subject: [PATCH 21/27] x86/speculation: Support 'mitigations=' cmdline option
   5
   6 commit d68be4c4d31295ff6ae34a8ddfaa4c1a8ff42812 upstream
   7
   8 Configure x86 runtime CPU speculation bug mitigations in accordance with
   9 the 'mitigations=' cmdline option.  This affects Meltdown, Spectre v2,
  10 Speculative Store Bypass, and L1TF.
  11
  12 The default behavior is unchanged.
  13
  14 Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
  15 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  16 Tested-by: Jiri Kosina <jkosina@suse.cz> (on x86)
  17 Reviewed-by: Jiri Kosina <jkosina@suse.cz>
  18 Cc: Borislav Petkov <bp@alien8.de>
  19 Cc: "H . Peter Anvin" <hpa@zytor.com>
  20 Cc: Andy Lutomirski <luto@kernel.org>
  21 Cc: Peter Zijlstra <peterz@infradead.org>
  22 Cc: Jiri Kosina <jikos@kernel.org>
  23 Cc: Waiman Long <longman@redhat.com>
  24 Cc: Andrea Arcangeli <aarcange@redhat.com>
  25 Cc: Jon Masters <jcm@redhat.com>
  26 Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
  27 Cc: Paul Mackerras <paulus@samba.org>
  28 Cc: Michael Ellerman <mpe@ellerman.id.au>
  29 Cc: linuxppc-dev@lists.ozlabs.org
  30 Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
  31 Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
  32 Cc: linux-s390@vger.kernel.org
  33 Cc: Catalin Marinas <catalin.marinas@arm.com>
  34 Cc: Will Deacon <will.deacon@arm.com>
  35 Cc: linux-arm-kernel@lists.infradead.org
  36 Cc: linux-arch@vger.kernel.org
  37 Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  38 Cc: Tyler Hicks <tyhicks@canonical.com>
  39 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  40 Cc: Randy Dunlap <rdunlap@infradead.org>
  41 Cc: Steven Price <steven.price@arm.com>
  42 Cc: Phil Auld <pauld@redhat.com>
  43 Link: https://lkml.kernel.org/r/6616d0ae169308516cfdf5216bedd169f8a8291b.1555085500.git.jpoimboe@redhat.com
  44 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  45 ---
  46  Documentation/admin-guide/kernel-parameters.txt | 16 +++++++++++-----
  47  arch/x86/kernel/cpu/bugs.c                      | 11 +++++++++--
  48  arch/x86/mm/pti.c                               |  4 +++-
  49  3 files changed, 23 insertions(+), 8 deletions(-)
  50
  51 diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
  52 index df6d9a7c1724..59a1181e52b8 100644
  53 --- a/Documentation/admin-guide/kernel-parameters.txt
  54 +++ b/Documentation/admin-guide/kernel-parameters.txt
  55 @@ -2540,15 +2540,20 @@
  56                         http://repo.or.cz/w/linux-2.6/mini2440.git
  57
  58         mitigations=
  59 -                       Control optional mitigations for CPU vulnerabilities.
  60 -                       This is a set of curated, arch-independent options, each
  61 -                       of which is an aggregation of existing arch-specific
  62 -                       options.
  63 +                       [X86] Control optional mitigations for CPU
  64 +                       vulnerabilities.  This is a set of curated,
  65 +                       arch-independent options, each of which is an
  66 +                       aggregation of existing arch-specific options.
  67
  68                         off
  69                                 Disable all optional CPU mitigations.  This
  70                                 improves system performance, but it may also
  71                                 expose users to several CPU vulnerabilities.
  72 +                               Equivalent to: nopti [X86]
  73 +                                              nospectre_v2 [X86]
  74 +                                              spectre_v2_user=off [X86]
  75 +                                              spec_store_bypass_disable=off [X86]
  76 +                                              l1tf=off [X86]
  77
  78                         auto (default)
  79                                 Mitigate all CPU vulnerabilities, but leave SMT
  80 @@ -2556,12 +2561,13 @@
  81                                 users who don't want to be surprised by SMT
  82                                 getting disabled across kernel upgrades, or who
  83                                 have other ways of avoiding SMT-based attacks.
  84 -                               This is the default behavior.
  85 +                               Equivalent to: (default behavior)
  86
  87                         auto,nosmt
  88                                 Mitigate all CPU vulnerabilities, disabling SMT
  89                                 if needed.  This is for users who always want to
  90                                 be fully mitigated, even if it means losing SMT.
  91 +                               Equivalent to: l1tf=flush,nosmt [X86]
  92
  93         mminit_loglevel=
  94                         [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  95 diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
  96 index 04c140ac36af..7c79672234e4 100644
  97 --- a/arch/x86/kernel/cpu/bugs.c
  98 +++ b/arch/x86/kernel/cpu/bugs.c
  99 @@ -506,7 +506,8 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 100         char arg[20];
 101         int ret, i;
 102
 103 -       if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
 104 +       if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") ||
 105 +           cpu_mitigations_off())
 106                 return SPECTRE_V2_CMD_NONE;
 107
 108         ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
 109 @@ -771,7 +772,8 @@ static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
 110         char arg[20];
 111         int ret, i;
 112
 113 -       if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable")) {
 114 +       if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable") ||
 115 +           cpu_mitigations_off()) {
 116                 return SPEC_STORE_BYPASS_CMD_NONE;
 117         } else {
 118                 ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable",
 119 @@ -1095,6 +1097,11 @@ static void __init l1tf_select_mitigation(void)
 120         if (!boot_cpu_has_bug(X86_BUG_L1TF))
 121                 return;
 122
 123 +       if (cpu_mitigations_off())
 124 +               l1tf_mitigation = L1TF_MITIGATION_OFF;
 125 +       else if (cpu_mitigations_auto_nosmt())
 126 +               l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
 127 +
 128         override_cache_bits(&boot_cpu_data);
 129
 130         switch (l1tf_mitigation) {
 131 diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
 132 index 4fee5c3003ed..5890f09bfc19 100644
 133 --- a/arch/x86/mm/pti.c
 134 +++ b/arch/x86/mm/pti.c
 135 @@ -35,6 +35,7 @@
 136  #include <linux/spinlock.h>
 137  #include <linux/mm.h>
 138  #include <linux/uaccess.h>
 139 +#include <linux/cpu.h>
 140
 141  #include <asm/cpufeature.h>
 142  #include <asm/hypervisor.h>
 143 @@ -115,7 +116,8 @@ void __init pti_check_boottime_disable(void)
 144                 }
 145         }
 146
 147 -       if (cmdline_find_option_bool(boot_command_line, "nopti")) {
 148 +       if (cmdline_find_option_bool(boot_command_line, "nopti") ||
 149 +           cpu_mitigations_off()) {
 150                 pti_mode = PTI_FORCE_OFF;
 151                 pti_print_if_insecure("disabled on command line.");
 152                 return;
 153 --
 154 2.21.0
 155