Re: Linux 6.8.1

From: Sasha Levin
Date: Fri Mar 15 2024 - 14:51:04 EST

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index a1db6db475055..710d47be11e04 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -516,6 +516,7 @@ What: /sys/devices/system/cpu/vulnerabilities
/sys/devices/system/cpu/vulnerabilities/mds
/sys/devices/system/cpu/vulnerabilities/meltdown
/sys/devices/system/cpu/vulnerabilities/mmio_stale_data
+ /sys/devices/system/cpu/vulnerabilities/reg_file_data_sampling
/sys/devices/system/cpu/vulnerabilities/retbleed
/sys/devices/system/cpu/vulnerabilities/spec_store_bypass
/sys/devices/system/cpu/vulnerabilities/spectre_v1
diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst
index de99caabf65a3..ff0b440ef2dc9 100644
--- a/Documentation/admin-guide/hw-vuln/index.rst
+++ b/Documentation/admin-guide/hw-vuln/index.rst
@@ -21,3 +21,4 @@ are configurable at compile, boot or run time.
cross-thread-rsb
srso
gather_data_sampling
+ reg-file-data-sampling
diff --git a/Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst b/Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
new file mode 100644
index 0000000000000..0585d02b9a6cb
--- /dev/null
+++ b/Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
@@ -0,0 +1,104 @@
+==================================
+Register File Data Sampling (RFDS)
+==================================
+
+Register File Data Sampling (RFDS) is a microarchitectural vulnerability that
+only affects Intel Atom parts(also branded as E-cores). RFDS may allow
+a malicious actor to infer data values previously used in floating point
+registers, vector registers, or integer registers. RFDS does not provide the
+ability to choose which data is inferred. CVE-2023-28746 is assigned to RFDS.
+
+Affected Processors
+===================
+Below is the list of affected Intel processors [#f1]_:
+
+ =================== ============
+ Common name Family_Model
+ =================== ============
+ ATOM_GOLDMONT 06_5CH
+ ATOM_GOLDMONT_D 06_5FH
+ ATOM_GOLDMONT_PLUS 06_7AH
+ ATOM_TREMONT_D 06_86H
+ ATOM_TREMONT 06_96H
+ ALDERLAKE 06_97H
+ ALDERLAKE_L 06_9AH
+ ATOM_TREMONT_L 06_9CH
+ RAPTORLAKE 06_B7H
+ RAPTORLAKE_P 06_BAH
+ ATOM_GRACEMONT 06_BEH
+ RAPTORLAKE_S 06_BFH
+ =================== ============
+
+As an exception to this table, Intel Xeon E family parts ALDERLAKE(06_97H) and
+RAPTORLAKE(06_B7H) codenamed Catlow are not affected. They are reported as
+vulnerable in Linux because they share the same family/model with an affected
+part. Unlike their affected counterparts, they do not enumerate RFDS_CLEAR or
+CPUID.HYBRID. This information could be used to distinguish between the
+affected and unaffected parts, but it is deemed not worth adding complexity as
+the reporting is fixed automatically when these parts enumerate RFDS_NO.
+
+Mitigation
+==========
+Intel released a microcode update that enables software to clear sensitive
+information using the VERW instruction. Like MDS, RFDS deploys the same
+mitigation strategy to force the CPU to clear the affected buffers before an
+attacker can extract the secrets. This is achieved by using the otherwise
+unused and obsolete VERW instruction in combination with a microcode update.
+The microcode clears the affected CPU buffers when the VERW instruction is
+executed.
+
+Mitigation points
+-----------------
+VERW is executed by the kernel before returning to user space, and by KVM
+before VMentry. None of the affected cores support SMT, so VERW is not required
+at C-state transitions.
+
+New bits in IA32_ARCH_CAPABILITIES
+----------------------------------
+Newer processors and microcode update on existing affected processors added new
+bits to IA32_ARCH_CAPABILITIES MSR. These bits can be used to enumerate
+vulnerability and mitigation capability:
+
+- Bit 27 - RFDS_NO - When set, processor is not affected by RFDS.
+- Bit 28 - RFDS_CLEAR - When set, processor is affected by RFDS, and has the
+ microcode that clears the affected buffers on VERW execution.
+
+Mitigation control on the kernel command line
+---------------------------------------------
+The kernel command line allows to control RFDS mitigation at boot time with the
+parameter "reg_file_data_sampling=". The valid arguments are:
+
+ ========== =================================================================
+ on If the CPU is vulnerable, enable mitigation; CPU buffer clearing
+ on exit to userspace and before entering a VM.
+ off Disables mitigation.
+ ========== =================================================================
+
+Mitigation default is selected by CONFIG_MITIGATION_RFDS.
+
+Mitigation status information
+-----------------------------
+The Linux kernel provides a sysfs interface to enumerate the current
+vulnerability status of the system: whether the system is vulnerable, and
+which mitigations are active. The relevant sysfs file is:
+
+ /sys/devices/system/cpu/vulnerabilities/reg_file_data_sampling
+
+The possible values in this file are:
+
+ .. list-table::
+
+ * - 'Not affected'
+ - The processor is not vulnerable
+ * - 'Vulnerable'
+ - The processor is vulnerable, but no mitigation enabled
+ * - 'Vulnerable: No microcode'
+ - The processor is vulnerable but microcode is not updated.
+ * - 'Mitigation: Clear Register File'
+ - The processor is vulnerable and the CPU buffer clearing mitigation is
+ enabled.
+
+References
+----------
+.. [#f1] Affected Processors
+ https://www.intel.com/content/www/us/en/developer/topic-technology/software-security-guidance/processors-affected-consolidated-product-cpu-model.html
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 31b3a25680d08..73062d47a462e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1150,6 +1150,26 @@
The filter can be disabled or changed to another
driver later using sysfs.

+ reg_file_data_sampling=
+ [X86] Controls mitigation for Register File Data
+ Sampling (RFDS) vulnerability. RFDS is a CPU
+ vulnerability which may allow userspace to infer
+ kernel data values previously stored in floating point
+ registers, vector registers, or integer registers.
+ RFDS only affects Intel Atom processors.
+
+ on: Turns ON the mitigation.
+ off: Turns OFF the mitigation.
+
+ This parameter overrides the compile time default set
+ by CONFIG_MITIGATION_RFDS. Mitigation cannot be
+ disabled when other VERW based mitigations (like MDS)
+ are enabled. In order to disable RFDS mitigation all
+ VERW based mitigations need to be disabled.
+
+ For details see:
+ Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
+
driver_async_probe= [KNL]
List of driver names to be probed asynchronously. *
matches with all driver names. If * is specified, the
@@ -3398,6 +3418,7 @@
nospectre_bhb [ARM64]
nospectre_v1 [X86,PPC]
nospectre_v2 [X86,PPC,S390,ARM64]
+ reg_file_data_sampling=off [X86]
retbleed=off [X86]
spec_store_bypass_disable=off [X86,PPC]
spectre_v2_user=off [X86]
diff --git a/Makefile b/Makefile
index c7ee53f4bf044..95b320ada47c4 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
VERSION = 6
PATCHLEVEL = 8
-SUBLEVEL = 0
+SUBLEVEL = 1
EXTRAVERSION =
NAME = Hurr durr I'ma ninja sloth

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5edec175b9bfc..637e337c332e4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2614,6 +2614,17 @@ config GDS_FORCE_MITIGATION

If in doubt, say N.

+config MITIGATION_RFDS
+ bool "RFDS Mitigation"
+ depends on CPU_SUP_INTEL
+ default y
+ help
+ Enable mitigation for Register File Data Sampling (RFDS) by default.
+ RFDS is a hardware vulnerability which affects Intel Atom CPUs. It
+ allows unprivileged speculative access to stale data previously
+ stored in floating point, vector and integer registers.
+ See also <file:Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst>
+
endif

config ARCH_HAS_ADD_PAGES
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 2b62cdd8dd122..8511aad595813 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -503,4 +503,5 @@
/* BUG word 2 */
#define X86_BUG_SRSO X86_BUG(1*32 + 0) /* AMD SRSO bug */
#define X86_BUG_DIV0 X86_BUG(1*32 + 1) /* AMD DIV0 speculation bug */
+#define X86_BUG_RFDS X86_BUG(1*32 + 2) /* CPU is vulnerable to Register File Data Sampling */
#endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index f1bd7b91b3c63..d1b5edaf6c34b 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -165,6 +165,14 @@
* CPU is not vulnerable to Gather
* Data Sampling (GDS).
*/
+#define ARCH_CAP_RFDS_NO BIT(27) /*
+ * Not susceptible to Register
+ * File Data Sampling.
+ */
+#define ARCH_CAP_RFDS_CLEAR BIT(28) /*
+ * VERW clears CPU Register
+ * File.
+ */

#define ARCH_CAP_XAPIC_DISABLE BIT(21) /*
* IA32_XAPIC_DISABLE_STATUS MSR
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 48d049cd74e71..01ac18f56147f 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -422,6 +422,13 @@ static void __init mmio_select_mitigation(void)
if (boot_cpu_has_bug(X86_BUG_MDS) || (boot_cpu_has_bug(X86_BUG_TAA) &&
boot_cpu_has(X86_FEATURE_RTM)))
setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
+
+ /*
+ * X86_FEATURE_CLEAR_CPU_BUF could be enabled by other VERW based
+ * mitigations, disable KVM-only mitigation in that case.
+ */
+ if (boot_cpu_has(X86_FEATURE_CLEAR_CPU_BUF))
+ static_branch_disable(&mmio_stale_data_clear);
else
static_branch_enable(&mmio_stale_data_clear);

@@ -473,6 +480,57 @@ static int __init mmio_stale_data_parse_cmdline(char *str)
}
early_param("mmio_stale_data", mmio_stale_data_parse_cmdline);

+#undef pr_fmt
+#define pr_fmt(fmt) "Register File Data Sampling: " fmt
+
+enum rfds_mitigations {
+ RFDS_MITIGATION_OFF,
+ RFDS_MITIGATION_VERW,
+ RFDS_MITIGATION_UCODE_NEEDED,
+};
+
+/* Default mitigation for Register File Data Sampling */
+static enum rfds_mitigations rfds_mitigation __ro_after_init =
+ IS_ENABLED(CONFIG_MITIGATION_RFDS) ? RFDS_MITIGATION_VERW : RFDS_MITIGATION_OFF;
+
+static const char * const rfds_strings[] = {
+ [RFDS_MITIGATION_OFF] = "Vulnerable",
+ [RFDS_MITIGATION_VERW] = "Mitigation: Clear Register File",
+ [RFDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode",
+};
+
+static void __init rfds_select_mitigation(void)
+{
+ if (!boot_cpu_has_bug(X86_BUG_RFDS) || cpu_mitigations_off()) {
+ rfds_mitigation = RFDS_MITIGATION_OFF;
+ return;
+ }
+ if (rfds_mitigation == RFDS_MITIGATION_OFF)
+ return;
+
+ if (x86_read_arch_cap_msr() & ARCH_CAP_RFDS_CLEAR)
+ setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
+ else
+ rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED;
+}
+
+static __init int rfds_parse_cmdline(char *str)
+{
+ if (!str)
+ return -EINVAL;
+
+ if (!boot_cpu_has_bug(X86_BUG_RFDS))
+ return 0;
+
+ if (!strcmp(str, "off"))
+ rfds_mitigation = RFDS_MITIGATION_OFF;
+ else if (!strcmp(str, "on"))
+ rfds_mitigation = RFDS_MITIGATION_VERW;
+
+ return 0;
+}
+early_param("reg_file_data_sampling", rfds_parse_cmdline);
+
#undef pr_fmt
#define pr_fmt(fmt) "" fmt

@@ -498,11 +556,19 @@ static void __init md_clear_update_mitigation(void)
taa_mitigation = TAA_MITIGATION_VERW;
taa_select_mitigation();
}
- if (mmio_mitigation == MMIO_MITIGATION_OFF &&
- boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) {
+ /*
+ * MMIO_MITIGATION_OFF is not checked here so that mmio_stale_data_clear
+ * gets updated correctly as per X86_FEATURE_CLEAR_CPU_BUF state.
+ */
+ if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) {
mmio_mitigation = MMIO_MITIGATION_VERW;
mmio_select_mitigation();
}
+ if (rfds_mitigation == RFDS_MITIGATION_OFF &&
+ boot_cpu_has_bug(X86_BUG_RFDS)) {
+ rfds_mitigation = RFDS_MITIGATION_VERW;
+ rfds_select_mitigation();
+ }
out:
if (boot_cpu_has_bug(X86_BUG_MDS))
pr_info("MDS: %s\n", mds_strings[mds_mitigation]);
@@ -512,6 +578,8 @@ static void __init md_clear_update_mitigation(void)
pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]);
else if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
pr_info("MMIO Stale Data: Unknown: No mitigations\n");
+ if (boot_cpu_has_bug(X86_BUG_RFDS))
+ pr_info("Register File Data Sampling: %s\n", rfds_strings[rfds_mitigation]);
}

static void __init md_clear_select_mitigation(void)
@@ -519,11 +587,12 @@ static void __init md_clear_select_mitigation(void)
mds_select_mitigation();
taa_select_mitigation();
mmio_select_mitigation();
+ rfds_select_mitigation();

/*
- * As MDS, TAA and MMIO Stale Data mitigations are inter-related, update
- * and print their mitigation after MDS, TAA and MMIO Stale Data
- * mitigation selection is done.
+ * As these mitigations are inter-related and rely on VERW instruction
+ * to clear the microarchitural buffers, update and print their status
+ * after mitigation selection is done for each of these vulnerabilities.
*/
md_clear_update_mitigation();
}
@@ -2612,6 +2681,11 @@ static ssize_t mmio_stale_data_show_state(char *buf)
sched_smt_active() ? "vulnerable" : "disabled");
}

+static ssize_t rfds_show_state(char *buf)
+{
+ return sysfs_emit(buf, "%s\n", rfds_strings[rfds_mitigation]);
+}
+
static char *stibp_state(void)
{
if (spectre_v2_in_eibrs_mode(spectre_v2_enabled) &&
@@ -2771,6 +2845,9 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
case X86_BUG_GDS:
return gds_show_state(buf);

+ case X86_BUG_RFDS:
+ return rfds_show_state(buf);
+
default:
break;
}
@@ -2845,4 +2922,9 @@ ssize_t cpu_show_gds(struct device *dev, struct device_attribute *attr, char *bu
{
return cpu_show_common(dev, attr, buf, X86_BUG_GDS);
}
+
+ssize_t cpu_show_reg_file_data_sampling(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ return cpu_show_common(dev, attr, buf, X86_BUG_RFDS);
+}
#endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index fbc4e60d027cb..40d8c110bb32e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1267,6 +1267,8 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
#define SRSO BIT(5)
/* CPU is affected by GDS */
#define GDS BIT(6)
+/* CPU is affected by Register File Data Sampling */
+#define RFDS BIT(7)

static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_INTEL_STEPPINGS(IVYBRIDGE, X86_STEPPING_ANY, SRBDS),
@@ -1294,9 +1296,18 @@ static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_INTEL_STEPPINGS(TIGERLAKE, X86_STEPPING_ANY, GDS),
VULNBL_INTEL_STEPPINGS(LAKEFIELD, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED),
VULNBL_INTEL_STEPPINGS(ROCKETLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS),
- VULNBL_INTEL_STEPPINGS(ATOM_TREMONT, X86_STEPPING_ANY, MMIO | MMIO_SBDS),
- VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_D, X86_STEPPING_ANY, MMIO),
- VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE_L, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE_P, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE_S, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_GRACEMONT, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_TREMONT, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_D, X86_STEPPING_ANY, MMIO | RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_GOLDMONT, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_GOLDMONT_D, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_GOLDMONT_PLUS, X86_STEPPING_ANY, RFDS),

VULNBL_AMD(0x15, RETBLEED),
VULNBL_AMD(0x16, RETBLEED),
@@ -1330,6 +1341,24 @@ static bool arch_cap_mmio_immune(u64 ia32_cap)
ia32_cap & ARCH_CAP_SBDR_SSDP_NO);
}

+static bool __init vulnerable_to_rfds(u64 ia32_cap)
+{
+ /* The "immunity" bit trumps everything else: */
+ if (ia32_cap & ARCH_CAP_RFDS_NO)
+ return false;
+
+ /*
+ * VMMs set ARCH_CAP_RFDS_CLEAR for processors not in the blacklist to
+ * indicate that mitigation is needed because guest is running on a
+ * vulnerable hardware or may migrate to such hardware:
+ */
+ if (ia32_cap & ARCH_CAP_RFDS_CLEAR)
+ return true;
+
+ /* Only consult the blacklist when there is no enumeration: */
+ return cpu_matches(cpu_vuln_blacklist, RFDS);
+}
+
static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
{
u64 ia32_cap = x86_read_arch_cap_msr();
@@ -1441,6 +1470,9 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
boot_cpu_has(X86_FEATURE_AVX))
setup_force_cpu_bug(X86_BUG_GDS);

+ if (vulnerable_to_rfds(ia32_cap))
+ setup_force_cpu_bug(X86_BUG_RFDS);
+
if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
return;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e02cc710f56de..ffe580169c93f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1623,7 +1623,8 @@ static bool kvm_is_immutable_feature_msr(u32 msr)
ARCH_CAP_SKIP_VMENTRY_L1DFLUSH | ARCH_CAP_SSB_NO | ARCH_CAP_MDS_NO | \
ARCH_CAP_PSCHANGE_MC_NO | ARCH_CAP_TSX_CTRL_MSR | ARCH_CAP_TAA_NO | \
ARCH_CAP_SBDR_SSDP_NO | ARCH_CAP_FBSDP_NO | ARCH_CAP_PSDP_NO | \
- ARCH_CAP_FB_CLEAR | ARCH_CAP_RRSBA | ARCH_CAP_PBRSB_NO | ARCH_CAP_GDS_NO)
+ ARCH_CAP_FB_CLEAR | ARCH_CAP_RRSBA | ARCH_CAP_PBRSB_NO | ARCH_CAP_GDS_NO | \
+ ARCH_CAP_RFDS_NO | ARCH_CAP_RFDS_CLEAR)

static u64 kvm_get_arch_capabilities(void)
{
@@ -1655,6 +1656,8 @@ static u64 kvm_get_arch_capabilities(void)
data |= ARCH_CAP_SSB_NO;
if (!boot_cpu_has_bug(X86_BUG_MDS))
data |= ARCH_CAP_MDS_NO;
+ if (!boot_cpu_has_bug(X86_BUG_RFDS))
+ data |= ARCH_CAP_RFDS_NO;

if (!boot_cpu_has(X86_FEATURE_RTM)) {
/*
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 47de0f140ba65..0b33e81f9c9b6 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -588,6 +588,7 @@ CPU_SHOW_VULN_FALLBACK(mmio_stale_data);
CPU_SHOW_VULN_FALLBACK(retbleed);
CPU_SHOW_VULN_FALLBACK(spec_rstack_overflow);
CPU_SHOW_VULN_FALLBACK(gds);
+CPU_SHOW_VULN_FALLBACK(reg_file_data_sampling);

static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
@@ -602,6 +603,7 @@ 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(spec_rstack_overflow, 0444, cpu_show_spec_rstack_overflow, NULL);
static DEVICE_ATTR(gather_data_sampling, 0444, cpu_show_gds, NULL);
+static DEVICE_ATTR(reg_file_data_sampling, 0444, cpu_show_reg_file_data_sampling, NULL);

static struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_meltdown.attr,
@@ -617,6 +619,7 @@ static struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_retbleed.attr,
&dev_attr_spec_rstack_overflow.attr,
&dev_attr_gather_data_sampling.attr,
+ &dev_attr_reg_file_data_sampling.attr,
NULL
};

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index dcb89c9871640..8654714421a0d 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -75,6 +75,8 @@ extern ssize_t cpu_show_spec_rstack_overflow(struct device *dev,
struct device_attribute *attr, char *buf);
extern ssize_t cpu_show_gds(struct device *dev,
struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_reg_file_data_sampling(struct device *dev,
+ struct device_attribute *attr, char *buf);

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