releases/4.4.180/x86-speculation-mds-add-smt-warning-message.patch

   1 From foo@baz Tue 14 May 2019 08:29:35 PM CEST
   2 From: Josh Poimboeuf <jpoimboe@redhat.com>
   3 Date: Tue, 2 Apr 2019 10:00:51 -0500
   4 Subject: x86/speculation/mds: Add SMT warning message
   5
   6 From: Josh Poimboeuf <jpoimboe@redhat.com>
   7
   8 commit 39226ef02bfb43248b7db12a4fdccb39d95318e3 upstream.
   9
  10 MDS is vulnerable with SMT.  Make that clear with a one-time printk
  11 whenever SMT first gets enabled.
  12
  13 Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
  14 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  15 Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
  16 Acked-by: Jiri Kosina <jkosina@suse.cz>
  17 Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
  18 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  19 ---
  20  arch/x86/kernel/cpu/bugs.c |    8 ++++++++
  21  1 file changed, 8 insertions(+)
  22
  23 --- a/arch/x86/kernel/cpu/bugs.c
  24 +++ b/arch/x86/kernel/cpu/bugs.c
  25 @@ -646,6 +646,9 @@ static void update_indir_branch_cond(voi
  26                 static_branch_disable(&switch_to_cond_stibp);
  27  }
  28
  29 +#undef pr_fmt
  30 +#define pr_fmt(fmt) fmt
  31 +
  32  /* Update the static key controlling the MDS CPU buffer clear in idle */
  33  static void update_mds_branch_idle(void)
  34  {
  35 @@ -666,6 +669,8 @@ static void update_mds_branch_idle(void)
  36                 static_branch_disable(&mds_idle_clear);
  37  }
  38
  39 +#define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"
  40 +
  41  void arch_smt_update(void)
  42  {
  43         /* Enhanced IBRS implies STIBP. No update required. */
  44 @@ -689,6 +694,8 @@ void arch_smt_update(void)
  45         switch (mds_mitigation) {
  46         case MDS_MITIGATION_FULL:
  47         case MDS_MITIGATION_VMWERV:
  48 +               if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY))
  49 +                       pr_warn_once(MDS_MSG_SMT);
  50                 update_mds_branch_idle();
  51                 break;
  52         case MDS_MITIGATION_OFF:
  53 @@ -1069,6 +1076,7 @@ static void __init l1tf_select_mitigatio
  54         setup_force_cpu_cap(X86_FEATURE_L1TF_PTEINV);
  55  }
  56  #undef pr_fmt
  57 +#define pr_fmt(fmt) fmt
  58
  59  #ifdef CONFIG_SYSFS
  60