linux-kernel - [PATCH] x86/cpu/amd: Report zenbleed in sysfs

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Date:   Thu, 27 Jul 2023 10:54:46 +0300
From:   Nikolay Borisov <nik.borisov@...e.com>
To:     x86@...nel.org
Cc:     bp@...en8.de, tglx@...utronix.de, linux-kernel@...r.kernel.org,
        Nikolay Borisov <nik.borisov@...e.com>
Subject: [PATCH] x86/cpu/amd: Report zenbleed in sysfs

Initial submission of Zenbleed fix omitted reporting the bug in sysfs.
There's no reason why it shouldn't be reported so let's add it among
the other vulnerabilities.

Signed-off-by: Nikolay Borisov <nik.borisov@...e.com>
---
 .../ABI/testing/sysfs-devices-system-cpu          |  1 +
 arch/x86/kernel/cpu/amd.c                         | 15 +++++++++++++++
 drivers/base/cpu.c                                |  8 ++++++++
 include/linux/cpu.h                               |  2 ++
 4 files changed, 26 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index ecd585ca2d50..30bb4196e451 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -524,6 +524,7 @@ What:		/sys/devices/system/cpu/vulnerabilities
 		/sys/devices/system/cpu/vulnerabilities/itlb_multihit
 		/sys/devices/system/cpu/vulnerabilities/mmio_stale_data
 		/sys/devices/system/cpu/vulnerabilities/retbleed
+		/sys/devices/system/cpu/vulnerabilities/zenbleed
 Date:		January 2018
 Contact:	Linux kernel mailing list <linux-kernel@...r.kernel.org>
 Description:	Information about CPU vulnerabilities
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 26ad7ca423e7..3ab9745eafc5 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1279,6 +1279,21 @@ u32 amd_get_highest_perf(void)
 }
 EXPORT_SYMBOL_GPL(amd_get_highest_perf);
 
+ssize_t cpu_show_zenbleed(struct device *dev, struct device_attribute *attr, char *buf)
+{
+
+	if (!cpu_has_amd_erratum(&boot_cpu_data, amd_zenbleed) ||
+	    !boot_cpu_has(X86_FEATURE_AVX) ||
+	    boot_cpu_has(X86_FEATURE_HYPERVISOR))
+		return sysfs_emit(buf, "Not affected\n");
+
+	if (!cpu_has_zenbleed_microcode()) {
+		return sysfs_emit(buf, "Mitigation: Chickenbit\n");
+	} else {
+		return sysfs_emit(buf, "Mitigation: Microcode\n");
+	}
+}
+
 static void zenbleed_check_cpu(void *unused)
 {
 	struct cpuinfo_x86 *c = &cpu_data(smp_processor_id());
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index c1815b9dae68..49c963a0f362 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -577,6 +577,12 @@ ssize_t __weak cpu_show_retbleed(struct device *dev,
 	return sysfs_emit(buf, "Not affected\n");
 }
 
+ssize_t __weak cpu_show_zenbleed(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(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);
@@ -588,6 +594,7 @@ static DEVICE_ATTR(itlb_multihit, 0444, cpu_show_itlb_multihit, NULL);
 static DEVICE_ATTR(srbds, 0444, cpu_show_srbds, NULL);
 static DEVICE_ATTR(mmio_stale_data, 0444, cpu_show_mmio_stale_data, NULL);
 static DEVICE_ATTR(retbleed, 0444, cpu_show_retbleed, NULL);
+static DEVICE_ATTR(zenbleed, 0444, cpu_show_zenbleed, NULL);
 
 static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 	&dev_attr_meltdown.attr,
@@ -601,6 +608,7 @@ static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 	&dev_attr_srbds.attr,
 	&dev_attr_mmio_stale_data.attr,
 	&dev_attr_retbleed.attr,
+	&dev_attr_zenbleed.attr,
 	NULL
 };
 
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 6e6e57ec69e8..8ed8fa142067 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -70,6 +70,8 @@ extern ssize_t cpu_show_mmio_stale_data(struct device *dev,
 					char *buf);
 extern ssize_t cpu_show_retbleed(struct device *dev,
 				 struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_zenbleed(struct device *dev,
+				 struct device_attribute *attr, char *buf);
 
 extern __printf(4, 5)
 struct device *cpu_device_create(struct device *parent, void *drvdata,
-- 
2.34.1