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-rw-r--r--Documentation/ABI/testing/sysfs-devices-system-cpu1
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt20
-rw-r--r--arch/x86/include/asm/cpufeatures.h2
-rw-r--r--arch/x86/include/asm/msr-index.h4
-rw-r--r--arch/x86/kernel/cpu/bugs.c106
-rw-r--r--arch/x86/kernel/cpu/common.c31
-rw-r--r--arch/x86/kernel/cpu/cpu.h1
-rw-r--r--drivers/base/cpu.c8
8 files changed, 173 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index b492fb6057c9..b9c14c11efc5 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -478,6 +478,7 @@ What: /sys/devices/system/cpu/vulnerabilities
/sys/devices/system/cpu/vulnerabilities/spec_store_bypass
/sys/devices/system/cpu/vulnerabilities/l1tf
/sys/devices/system/cpu/vulnerabilities/mds
+ /sys/devices/system/cpu/vulnerabilities/srbds
/sys/devices/system/cpu/vulnerabilities/tsx_async_abort
/sys/devices/system/cpu/vulnerabilities/itlb_multihit
Date: January 2018
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1a5101b7e853..30752db57587 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4415,6 +4415,26 @@
spia_pedr=
spia_peddr=
+ srbds= [X86,INTEL]
+ Control the Special Register Buffer Data Sampling
+ (SRBDS) mitigation.
+
+ Certain CPUs are vulnerable to an MDS-like
+ exploit which can leak bits from the random
+ number generator.
+
+ By default, this issue is mitigated by
+ microcode. However, the microcode fix can cause
+ the RDRAND and RDSEED instructions to become
+ much slower. Among other effects, this will
+ result in reduced throughput from /dev/urandom.
+
+ The microcode mitigation can be disabled with
+ the following option:
+
+ off: Disable mitigation and remove
+ performance impact to RDRAND and RDSEED
+
srcutree.counter_wrap_check [KNL]
Specifies how frequently to check for
grace-period sequence counter wrap for the
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 8c13b99b9507..9f03ac233566 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -347,6 +347,7 @@
/* Intel-defined CPU features, CPUID level 0x00000007:0 (EDX), word 18 */
#define X86_FEATURE_AVX512_4VNNIW (18*32+ 2) /* AVX-512 Neural Network Instructions */
#define X86_FEATURE_AVX512_4FMAPS (18*32+ 3) /* AVX-512 Multiply Accumulation Single precision */
+#define X86_FEATURE_SRBDS_CTRL (18*32+ 9) /* "" SRBDS mitigation MSR available */
#define X86_FEATURE_TSX_FORCE_ABORT (18*32+13) /* "" TSX_FORCE_ABORT */
#define X86_FEATURE_MD_CLEAR (18*32+10) /* VERW clears CPU buffers */
#define X86_FEATURE_PCONFIG (18*32+18) /* Intel PCONFIG */
@@ -391,5 +392,6 @@
#define X86_BUG_SWAPGS X86_BUG(21) /* CPU is affected by speculation through SWAPGS */
#define X86_BUG_TAA X86_BUG(22) /* CPU is affected by TSX Async Abort(TAA) */
#define X86_BUG_ITLB_MULTIHIT X86_BUG(23) /* CPU may incur MCE during certain page attribute changes */
+#define X86_BUG_SRBDS X86_BUG(24) /* CPU may leak RNG bits if not mitigated */
#endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index d2c25a13e1ce..5bb11a8c245e 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -110,6 +110,10 @@
#define TSX_CTRL_RTM_DISABLE BIT(0) /* Disable RTM feature */
#define TSX_CTRL_CPUID_CLEAR BIT(1) /* Disable TSX enumeration */
+/* SRBDS support */
+#define MSR_IA32_MCU_OPT_CTRL 0x00000123
+#define RNGDS_MITG_DIS BIT(0)
+
#define MSR_IA32_SYSENTER_CS 0x00000174
#define MSR_IA32_SYSENTER_ESP 0x00000175
#define MSR_IA32_SYSENTER_EIP 0x00000176
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 2d23a448e72d..cf07437cd106 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -41,6 +41,7 @@ static void __init l1tf_select_mitigation(void);
static void __init mds_select_mitigation(void);
static void __init mds_print_mitigation(void);
static void __init taa_select_mitigation(void);
+static void __init srbds_select_mitigation(void);
/* The base value of the SPEC_CTRL MSR that always has to be preserved. */
u64 x86_spec_ctrl_base;
@@ -108,6 +109,7 @@ void __init check_bugs(void)
l1tf_select_mitigation();
mds_select_mitigation();
taa_select_mitigation();
+ srbds_select_mitigation();
/*
* As MDS and TAA mitigations are inter-related, print MDS
@@ -391,6 +393,97 @@ static int __init tsx_async_abort_parse_cmdline(char *str)
early_param("tsx_async_abort", tsx_async_abort_parse_cmdline);
#undef pr_fmt
+#define pr_fmt(fmt) "SRBDS: " fmt
+
+enum srbds_mitigations {
+ SRBDS_MITIGATION_OFF,
+ SRBDS_MITIGATION_UCODE_NEEDED,
+ SRBDS_MITIGATION_FULL,
+ SRBDS_MITIGATION_TSX_OFF,
+ SRBDS_MITIGATION_HYPERVISOR,
+};
+
+static enum srbds_mitigations srbds_mitigation __ro_after_init = SRBDS_MITIGATION_FULL;
+
+static const char * const srbds_strings[] = {
+ [SRBDS_MITIGATION_OFF] = "Vulnerable",
+ [SRBDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode",
+ [SRBDS_MITIGATION_FULL] = "Mitigation: Microcode",
+ [SRBDS_MITIGATION_TSX_OFF] = "Mitigation: TSX disabled",
+ [SRBDS_MITIGATION_HYPERVISOR] = "Unknown: Dependent on hypervisor status",
+};
+
+static bool srbds_off;
+
+void update_srbds_msr(void)
+{
+ u64 mcu_ctrl;
+
+ if (!boot_cpu_has_bug(X86_BUG_SRBDS))
+ return;
+
+ if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
+ return;
+
+ if (srbds_mitigation == SRBDS_MITIGATION_UCODE_NEEDED)
+ return;
+
+ rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
+
+ switch (srbds_mitigation) {
+ case SRBDS_MITIGATION_OFF:
+ case SRBDS_MITIGATION_TSX_OFF:
+ mcu_ctrl |= RNGDS_MITG_DIS;
+ break;
+ case SRBDS_MITIGATION_FULL:
+ mcu_ctrl &= ~RNGDS_MITG_DIS;
+ break;
+ default:
+ break;
+ }
+
+ wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
+}
+
+static void __init srbds_select_mitigation(void)
+{
+ u64 ia32_cap;
+
+ if (!boot_cpu_has_bug(X86_BUG_SRBDS))
+ return;
+
+ /*
+ * Check to see if this is one of the MDS_NO systems supporting
+ * TSX that are only exposed to SRBDS when TSX is enabled.
+ */
+ ia32_cap = x86_read_arch_cap_msr();
+ if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM))
+ srbds_mitigation = SRBDS_MITIGATION_TSX_OFF;
+ else if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
+ srbds_mitigation = SRBDS_MITIGATION_HYPERVISOR;
+ else if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL))
+ srbds_mitigation = SRBDS_MITIGATION_UCODE_NEEDED;
+ else if (cpu_mitigations_off() || srbds_off)
+ srbds_mitigation = SRBDS_MITIGATION_OFF;
+
+ update_srbds_msr();
+ pr_info("%s\n", srbds_strings[srbds_mitigation]);
+}
+
+static int __init srbds_parse_cmdline(char *str)
+{
+ if (!str)
+ return -EINVAL;
+
+ if (!boot_cpu_has_bug(X86_BUG_SRBDS))
+ return 0;
+
+ srbds_off = !strcmp(str, "off");
+ return 0;
+}
+early_param("srbds", srbds_parse_cmdline);
+
+#undef pr_fmt
#define pr_fmt(fmt) "Spectre V1 : " fmt
enum spectre_v1_mitigation {
@@ -1491,6 +1584,11 @@ static char *ibpb_state(void)
return "";
}
+static ssize_t srbds_show_state(char *buf)
+{
+ return sprintf(buf, "%s\n", srbds_strings[srbds_mitigation]);
+}
+
static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
char *buf, unsigned int bug)
{
@@ -1535,6 +1633,9 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
case X86_BUG_ITLB_MULTIHIT:
return itlb_multihit_show_state(buf);
+ case X86_BUG_SRBDS:
+ return srbds_show_state(buf);
+
default:
break;
}
@@ -1581,4 +1682,9 @@ ssize_t cpu_show_itlb_multihit(struct device *dev, struct device_attribute *attr
{
return cpu_show_common(dev, attr, buf, X86_BUG_ITLB_MULTIHIT);
}
+
+ssize_t cpu_show_srbds(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ return cpu_show_common(dev, attr, buf, X86_BUG_SRBDS);
+}
#endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 375e1d459b68..2058e8c0e61d 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1013,6 +1013,27 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
{}
};
+#define VULNBL_INTEL_STEPPINGS(model, steppings, issues) \
+ X86_MATCH_VENDOR_FAM_MODEL_STEPPINGS_FEATURE(INTEL, 6, \
+ INTEL_FAM6_##model, steppings, \
+ X86_FEATURE_ANY, issues)
+
+#define SRBDS BIT(0)
+
+static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
+ VULNBL_INTEL_STEPPINGS(IVYBRIDGE, X86_STEPPING_ANY, SRBDS),
+ VULNBL_INTEL_STEPPINGS(HASWELL_CORE, X86_STEPPING_ANY, SRBDS),
+ VULNBL_INTEL_STEPPINGS(HASWELL_ULT, X86_STEPPING_ANY, SRBDS),
+ VULNBL_INTEL_STEPPINGS(HASWELL_GT3E, X86_STEPPING_ANY, SRBDS),
+ VULNBL_INTEL_STEPPINGS(BROADWELL_GT3E, X86_STEPPING_ANY, SRBDS),
+ VULNBL_INTEL_STEPPINGS(BROADWELL_CORE, X86_STEPPING_ANY, SRBDS),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE_MOBILE, X86_STEPPING_ANY, SRBDS),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE_DESKTOP, X86_STEPPING_ANY, SRBDS),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE_MOBILE, X86_STEPPINGS(0x0, 0xC), SRBDS),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE_DESKTOP,X86_STEPPINGS(0x0, 0xD), SRBDS),
+ {}
+};
+
static bool __init cpu_matches(const struct x86_cpu_id *table, unsigned long which)
{
const struct x86_cpu_id *m = x86_match_cpu(table);
@@ -1078,6 +1099,15 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
(ia32_cap & ARCH_CAP_TSX_CTRL_MSR)))
setup_force_cpu_bug(X86_BUG_TAA);
+ /*
+ * SRBDS affects CPUs which support RDRAND or RDSEED and are listed
+ * in the vulnerability blacklist.
+ */
+ if ((cpu_has(c, X86_FEATURE_RDRAND) ||
+ cpu_has(c, X86_FEATURE_RDSEED)) &&
+ cpu_matches(cpu_vuln_blacklist, SRBDS))
+ setup_force_cpu_bug(X86_BUG_SRBDS);
+
if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
return;
@@ -1522,6 +1552,7 @@ void identify_secondary_cpu(struct cpuinfo_x86 *c)
mtrr_ap_init();
validate_apic_and_package_id(c);
x86_spec_ctrl_setup_ap();
+ update_srbds_msr();
}
static __init int setup_noclflush(char *arg)
diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h
index 236582c90d3f..e89602d2aff5 100644
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -80,6 +80,7 @@ extern void detect_ht(struct cpuinfo_x86 *c);
unsigned int aperfmperf_get_khz(int cpu);
extern void x86_spec_ctrl_setup_ap(void);
+extern void update_srbds_msr(void);
extern u64 x86_read_arch_cap_msr(void);
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index f3ecf7418ed4..1df057486176 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -565,6 +565,12 @@ ssize_t __weak cpu_show_itlb_multihit(struct device *dev,
return sprintf(buf, "Not affected\n");
}
+ssize_t __weak cpu_show_srbds(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);
@@ -573,6 +579,7 @@ static DEVICE_ATTR(l1tf, 0444, cpu_show_l1tf, NULL);
static DEVICE_ATTR(mds, 0444, cpu_show_mds, NULL);
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 struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_meltdown.attr,
@@ -583,6 +590,7 @@ static struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_mds.attr,
&dev_attr_tsx_async_abort.attr,
&dev_attr_itlb_multihit.attr,
+ &dev_attr_srbds.attr,
NULL
};