| From 81e6aabbe552fa2db1a4a4c61d1d7c60495726e5 Mon Sep 17 00:00:00 2001 |
| From: Josh Poimboeuf <jpoimboe@redhat.com> |
| Date: Tue, 2 Apr 2019 10:00:51 -0500 |
| Subject: [PATCH 20/30] x86/speculation/mds: Add SMT warning message |
| |
| commit 39226ef02bfb43248b7db12a4fdccb39d95318e3 upstream |
| |
| MDS is vulnerable with SMT. Make that clear with a one-time printk |
| whenever SMT first gets enabled. |
| |
| Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Reviewed-by: Tyler Hicks <tyhicks@canonical.com> |
| Acked-by: Jiri Kosina <jkosina@suse.cz> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/x86/kernel/cpu/bugs.c | 8 ++++++++ |
| 1 file changed, 8 insertions(+) |
| |
| diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c |
| index 6ccbcac2cb1d..8e74282da80e 100644 |
| --- a/arch/x86/kernel/cpu/bugs.c |
| +++ b/arch/x86/kernel/cpu/bugs.c |
| @@ -659,6 +659,9 @@ static void update_indir_branch_cond(void) |
| static_branch_disable(&switch_to_cond_stibp); |
| } |
| |
| +#undef pr_fmt |
| +#define pr_fmt(fmt) fmt |
| + |
| /* Update the static key controlling the MDS CPU buffer clear in idle */ |
| static void update_mds_branch_idle(void) |
| { |
| @@ -679,6 +682,8 @@ static void update_mds_branch_idle(void) |
| static_branch_disable(&mds_idle_clear); |
| } |
| |
| +#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" |
| + |
| void arch_smt_update(void) |
| { |
| /* Enhanced IBRS implies STIBP. No update required. */ |
| @@ -702,6 +707,8 @@ void arch_smt_update(void) |
| switch (mds_mitigation) { |
| case MDS_MITIGATION_FULL: |
| case MDS_MITIGATION_VMWERV: |
| + if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY)) |
| + pr_warn_once(MDS_MSG_SMT); |
| update_mds_branch_idle(); |
| break; |
| case MDS_MITIGATION_OFF: |
| @@ -1131,6 +1138,7 @@ static int __init l1tf_cmdline(char *str) |
| early_param("l1tf", l1tf_cmdline); |
| |
| #undef pr_fmt |
| +#define pr_fmt(fmt) fmt |
| |
| #ifdef CONFIG_SYSFS |
| |
| -- |
| 2.21.0 |
| |
