[PATCH 5.4 11/15] x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data

Greg Kroah-Hartman
2022-06-14T18:49:05Z

From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>

commit 8d50cdf8b8341770bc6367bce40c0c1bb0e1d5b3 upstream

Add the sysfs reporting file for Processor MMIO Stale Data
vulnerability. It exposes the vulnerability and mitigation state similar
to the existing files for the other hardware vulnerabilities.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Documentation/ABI/testing/sysfs-devices-system-cpu | 1
arch/x86/kernel/cpu/bugs.c | 22 +++++++++++++++++++++
drivers/base/cpu.c | 8 +++++++
include/linux/cpu.h | 3 ++
4 files changed, 34 insertions(+)

--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -489,6 +489,7 @@ What: /sys/devices/system/cpu/vulnerabi
/sys/devices/system/cpu/vulnerabilities/srbds
/sys/devices/system/cpu/vulnerabilities/tsx_async_abort
/sys/devices/system/cpu/vulnerabilities/itlb_multihit
+ /sys/devices/system/cpu/vulnerabilities/mmio_stale_data
Date: January 2018
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Information about CPU vulnerabilities
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1820,6 +1820,20 @@ static ssize_t tsx_async_abort_show_stat
sched_smt_active() ? "vulnerable" : "disabled");
}

+static ssize_t mmio_stale_data_show_state(char *buf)
+{
+ if (mmio_mitigation == MMIO_MITIGATION_OFF)
+ return sysfs_emit(buf, "%s\n", mmio_strings[mmio_mitigation]);
+
+ if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
+ return sysfs_emit(buf, "%s; SMT Host state unknown\n",
+ mmio_strings[mmio_mitigation]);
+ }
+
+ return sysfs_emit(buf, "%s; SMT %s\n", mmio_strings[mmio_mitigation],
+ sched_smt_active() ? "vulnerable" : "disabled");
+}
+
static char *stibp_state(void)
{
if (spectre_v2_in_eibrs_mode(spectre_v2_enabled))
@@ -1920,6 +1934,9 @@ static ssize_t cpu_show_common(struct de
case X86_BUG_SRBDS:
return srbds_show_state(buf);

+ case X86_BUG_MMIO_STALE_DATA:
+ return mmio_stale_data_show_state(buf);
+
default:
break;
}
@@ -1971,4 +1988,9 @@ ssize_t cpu_show_srbds(struct device *de
{
return cpu_show_common(dev, attr, buf, X86_BUG_SRBDS);
}
+
+ssize_t cpu_show_mmio_stale_data(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA);
+}
#endif
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -568,6 +568,12 @@ ssize_t __weak cpu_show_srbds(struct dev
return sysfs_emit(buf, "Not affected\n");
}

+ssize_t __weak cpu_show_mmio_stale_data(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);
@@ -577,6 +583,7 @@ static DEVICE_ATTR(mds, 0444, cpu_show_m
static DEVICE_ATTR(tsx_async_abort, 0444, cpu_show_tsx_async_abort, NULL);
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 struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_meltdown.attr,
@@ -588,6 +595,7 @@ static struct attribute *cpu_root_vulner
&dev_attr_tsx_async_abort.attr,
&dev_attr_itlb_multihit.attr,
&dev_attr_srbds.attr,
+ &dev_attr_mmio_stale_data.attr,
NULL
};

--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -65,6 +65,9 @@ extern ssize_t cpu_show_tsx_async_abort(
extern ssize_t cpu_show_itlb_multihit(struct device *dev,
struct device_attribute *attr, char *buf);
extern ssize_t cpu_show_srbds(struct device *dev, struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_mmio_stale_data(struct device *dev,
+ struct device_attribute *attr,
+ char *buf);

extern __printf(4, 5)
struct device *cpu_device_create(struct device *parent, void *drvdata,