x86/speculation/mds: Print SMT vulnerable on MSBDS with mitigations off

This code is only for CPUs which are affected by MSBDS, but are *not*
affected by the other two MDS issues.

For such CPUs, enabling the mds_idle_clear mitigation is enough to
mitigate SMT.

However if user boots with 'mds=off' and still has SMT enabled, we should
not report that SMT is mitigated:

$cat /sys//devices/system/cpu/vulnerabilities/mds
Vulnerable; SMT mitigated

But rather:
Vulnerable; SMT vulnerable
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20190412215118.294906495@localhost.localdomain

CVE-2018-12126
CVE-2018-12127
CVE-2018-12130

(cherry picked from commit e2c3c947)
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/kernel/cpu/bugs.c

@@ -953,7 +953,8 @@ static ssize_t mds_show_state(char *buf)
 
 	if (boot_cpu_has(X86_BUG_MSBDS_ONLY)) {
 		return sprintf(buf, "%s; SMT %s\n", mds_strings[mds_mitigation],
-			       sched_smt_active() ? "mitigated" : "disabled");
+			       (mds_mitigation == MDS_MITIGATION_OFF ? "vulnerable" :
+			        sched_smt_active() ? "mitigated" : "disabled"));
 	}
 
 	return sprintf(buf, "%s; SMT %s\n", mds_strings[mds_mitigation],