[MODERATED] [PATCH v6 05/43] MDSv6

[Andi Kleen <andi@firstfloor.org>]

From: Andi Kleen <ak@linux.intel.com>
Subject:  x86/speculation/mds: Add sysfs reporting

Report mds mitigation state in sysfs vulnerabilities.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 .../ABI/testing/sysfs-devices-system-cpu      |  1 +
 arch/x86/kernel/cpu/bugs.c                    | 24 +++++++++++++++++++
 drivers/base/cpu.c                            |  8 +++++++
 3 files changed, 33 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 9605dbd4b5b5..2db5c3407fd6 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -484,6 +484,7 @@ What:		/sys/devices/system/cpu/vulnerabilities
 		/sys/devices/system/cpu/vulnerabilities/spectre_v2
 		/sys/devices/system/cpu/vulnerabilities/spec_store_bypass
 		/sys/devices/system/cpu/vulnerabilities/l1tf
+		/sys/devices/system/cpu/vulnerabilities/mds
 Date:		January 2018
 Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
 Description:	Information about CPU vulnerabilities
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b93565ab20b3..4114b4f94c1d 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1192,6 +1192,24 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
 		if (boot_cpu_has(X86_FEATURE_L1TF_PTEINV))
 			return l1tf_show_state(buf);
 		break;
+
+	case X86_BUG_MDS:
+		if (boot_cpu_has(X86_FEATURE_VERW) &&
+		    boot_cpu_has(X86_FEATURE_MD_CLEAR)) {
+			if (cpu_smt_control != CPU_SMT_ENABLED) {
+				/*
+				 * Avoid lying when a hypervisor didn't export
+				 * the SMT state.
+				 */
+				if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
+					return sprintf(buf,
+						"Mitigation: microcode, SMT potentially vulnerable\n");
+				return sprintf(buf, "Mitigation: microcode\n");
+			}
+			return sprintf(buf, "Mitigation: microcode, SMT vulnerable\n");
+		}
+		return sprintf(buf, "Vulnerable\n");
+
 	default:
 		break;
 	}
@@ -1223,4 +1241,10 @@ ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *b
 {
 	return cpu_show_common(dev, attr, buf, X86_BUG_L1TF);
 }
+
+ssize_t cpu_show_mds(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return cpu_show_common(dev, attr, buf, X86_BUG_MDS);
+}
+
 #endif
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index eb9443d5bae1..2fd6ca1021c2 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -546,11 +546,18 @@ ssize_t __weak cpu_show_l1tf(struct device *dev,
 	return sprintf(buf, "Not affected\n");
 }
 
+ssize_t __weak cpu_show_mds(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "Not affected\n");
+}
+
 static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
 static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
 static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
 static DEVICE_ATTR(spec_store_bypass, 0444, cpu_show_spec_store_bypass, NULL);
 static DEVICE_ATTR(l1tf, 0444, cpu_show_l1tf, NULL);
+static DEVICE_ATTR(mds, 0444, cpu_show_mds, NULL);
 
 static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 	&dev_attr_meltdown.attr,
@@ -558,6 +565,7 @@ static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 	&dev_attr_spectre_v2.attr,
 	&dev_attr_spec_store_bypass.attr,
 	&dev_attr_l1tf.attr,
+	&dev_attr_mds.attr,
 	NULL
 };
 
-- 
2.17.2