From 39226ef02bfb43248b7db12a4fdccb39d95318e3 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Tue, 2 Apr 2019 10:00:51 -0500 Subject: [PATCH] x86/speculation/mds: Add SMT warning message MDS is vulnerable with SMT. Make that clear with a one-time printk whenever SMT first gets enabled. Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Reviewed-by: Tyler Hicks Acked-by: Jiri Kosina --- 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 3f934ff..22a14d4 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -673,6 +673,9 @@ 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) { @@ -693,6 +696,8 @@ 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. */ @@ -717,6 +722,8 @@ 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: @@ -1149,6 +1156,7 @@ static int __init l1tf_cmdline(char *str) early_param("l1tf", l1tf_cmdline); #undef pr_fmt +#define pr_fmt(fmt) fmt #ifdef CONFIG_SYSFS -- 2.7.4