4.9-stable patches

[thirdparty/kernel/stable-queue.git] / queue-4.9 / 0066-x86-speculation-mds-Add-SMT-warning-message.patch

From d6a87300a6f1cba5faabcdb94d54fbef150d8e79 Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@redhat.com>
Date: Tue, 2 Apr 2019 10:00:51 -0500
Subject: [PATCH 66/76] 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: Ben Hutchings <ben@decadent.org.uk>
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 a725105a49d1..6a3fcacbb9a0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -667,6 +667,9 @@ 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)
 {
@@ -687,6 +690,8 @@ 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. */
@@ -710,6 +715,8 @@ 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:
@@ -1139,6 +1146,7 @@ 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