From: Josh Poimboeuf <jpoimboe@redhat.com>
Date: Tue, 2 Apr 2019 10:00:51 -0500
Subject: x86/speculation/mds: Add SMT warning message
Git-commit: 39226ef02bfb43248b7db12a4fdccb39d95318e3
Patch-mainline: v5.2-rc1
References: bsc#1111331, CVE-2018-12126, CVE-2018-12127, CVE-2018-12130, CVE-2019-11091
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>
Acked-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/cpu/bugs.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -800,6 +800,9 @@ static void update_indir_branch_cond(voi
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)
{
@@ -820,6 +823,8 @@ 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. */
@@ -843,6 +848,8 @@ 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: