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>
(cherry picked from commit 2dad2dcf7f7eab0e6d10d560e22fddd0a08b37b3)

Orabug: 29526900
CVE: CVE-2018-12126
CVE: CVE-2018-12130
CVE: CVE-2018-12127

Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Conflicts:
	arch/x86/kernel/cpu/bugs.c
bugs.c vs bugs_64.c: we do not have arch_smt_update. Squash the check in mds_select_mitigation.

diff --git a/arch/x86/kernel/cpu/bugs_64.c b/arch/x86/kernel/cpu/bugs_64.c
index 41b485b160b2d70f3da80fd987dc968926d73b31..a2a2021ea5117dee013dc175f6183aa29f071a63 100644 (file)
--- a/arch/x86/kernel/cpu/bugs_64.c
+++ b/arch/x86/kernel/cpu/bugs_64.c
@@ -1327,6 +1327,9 @@ static const char * const mds_strings[] = {
        [MDS_MITIGATION_VMWERV] = "Vulnerable: Clear CPU buffers attempted, no microcode",
 };
 
+#undef pr_fmt
+#define pr_fmt(fmt) "MDS: " fmt
+
 static void update_mds_branch_idle(void)
 {
        /*
@@ -1344,6 +1347,8 @@ 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"
+
 static void mds_select_mitigation(void)
 {
        char arg[12];
@@ -1374,12 +1379,17 @@ static void mds_select_mitigation(void)
                if (mds_nosmt && !boot_cpu_has(X86_BUG_MSBDS_ONLY))
                        cpu_smt_disable(false);
 
+               if (cpu_smt_control == CPU_SMT_ENABLED &&
+                   !boot_cpu_has(X86_BUG_MSBDS_ONLY))
+                       pr_warn_once(MDS_MSG_SMT);
+
                update_mds_branch_idle();
        }
        pr_info("%s\n", mds_strings[mds_mitigation]);
 }
 
 #undef pr_fmt
+#define pr_fmt(fmt) fmt
 
 #ifdef CONFIG_SYSFS