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Diffstat (limited to 'arch/x86/kernel/cpu/bugs.c')
-rw-r--r--arch/x86/kernel/cpu/bugs.c235
1 files changed, 199 insertions, 36 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d879a6c93609..74c62cc47a5f 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -41,8 +41,10 @@ static void __init spectre_v2_select_mitigation(void);
static void __init ssb_select_mitigation(void);
static void __init l1tf_select_mitigation(void);
static void __init mds_select_mitigation(void);
-static void __init mds_print_mitigation(void);
+static void __init md_clear_update_mitigation(void);
+static void __init md_clear_select_mitigation(void);
static void __init taa_select_mitigation(void);
+static void __init mmio_select_mitigation(void);
static void __init srbds_select_mitigation(void);
static void __init l1d_flush_select_mitigation(void);
@@ -85,6 +87,10 @@ EXPORT_SYMBOL_GPL(mds_idle_clear);
*/
DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush);
+/* Controls CPU Fill buffer clear before KVM guest MMIO accesses */
+DEFINE_STATIC_KEY_FALSE(mmio_stale_data_clear);
+EXPORT_SYMBOL_GPL(mmio_stale_data_clear);
+
void __init check_bugs(void)
{
identify_boot_cpu();
@@ -117,17 +123,10 @@ void __init check_bugs(void)
spectre_v2_select_mitigation();
ssb_select_mitigation();
l1tf_select_mitigation();
- mds_select_mitigation();
- taa_select_mitigation();
+ md_clear_select_mitigation();
srbds_select_mitigation();
l1d_flush_select_mitigation();
- /*
- * As MDS and TAA mitigations are inter-related, print MDS
- * mitigation until after TAA mitigation selection is done.
- */
- mds_print_mitigation();
-
arch_smt_update();
#ifdef CONFIG_X86_32
@@ -267,14 +266,6 @@ static void __init mds_select_mitigation(void)
}
}
-static void __init mds_print_mitigation(void)
-{
- if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off())
- return;
-
- pr_info("%s\n", mds_strings[mds_mitigation]);
-}
-
static int __init mds_cmdline(char *str)
{
if (!boot_cpu_has_bug(X86_BUG_MDS))
@@ -329,7 +320,7 @@ static void __init taa_select_mitigation(void)
/* TSX previously disabled by tsx=off */
if (!boot_cpu_has(X86_FEATURE_RTM)) {
taa_mitigation = TAA_MITIGATION_TSX_DISABLED;
- goto out;
+ return;
}
if (cpu_mitigations_off()) {
@@ -343,7 +334,7 @@ static void __init taa_select_mitigation(void)
*/
if (taa_mitigation == TAA_MITIGATION_OFF &&
mds_mitigation == MDS_MITIGATION_OFF)
- goto out;
+ return;
if (boot_cpu_has(X86_FEATURE_MD_CLEAR))
taa_mitigation = TAA_MITIGATION_VERW;
@@ -375,18 +366,6 @@ static void __init taa_select_mitigation(void)
if (taa_nosmt || cpu_mitigations_auto_nosmt())
cpu_smt_disable(false);
-
- /*
- * Update MDS mitigation, if necessary, as the mds_user_clear is
- * now enabled for TAA mitigation.
- */
- if (mds_mitigation == MDS_MITIGATION_OFF &&
- boot_cpu_has_bug(X86_BUG_MDS)) {
- mds_mitigation = MDS_MITIGATION_FULL;
- mds_select_mitigation();
- }
-out:
- pr_info("%s\n", taa_strings[taa_mitigation]);
}
static int __init tsx_async_abort_parse_cmdline(char *str)
@@ -411,6 +390,151 @@ 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) "MMIO Stale Data: " fmt
+
+enum mmio_mitigations {
+ MMIO_MITIGATION_OFF,
+ MMIO_MITIGATION_UCODE_NEEDED,
+ MMIO_MITIGATION_VERW,
+};
+
+/* Default mitigation for Processor MMIO Stale Data vulnerabilities */
+static enum mmio_mitigations mmio_mitigation __ro_after_init = MMIO_MITIGATION_VERW;
+static bool mmio_nosmt __ro_after_init = false;
+
+static const char * const mmio_strings[] = {
+ [MMIO_MITIGATION_OFF] = "Vulnerable",
+ [MMIO_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode",
+ [MMIO_MITIGATION_VERW] = "Mitigation: Clear CPU buffers",
+};
+
+static void __init mmio_select_mitigation(void)
+{
+ u64 ia32_cap;
+
+ if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) ||
+ cpu_mitigations_off()) {
+ mmio_mitigation = MMIO_MITIGATION_OFF;
+ return;
+ }
+
+ if (mmio_mitigation == MMIO_MITIGATION_OFF)
+ return;
+
+ ia32_cap = x86_read_arch_cap_msr();
+
+ /*
+ * Enable CPU buffer clear mitigation for host and VMM, if also affected
+ * by MDS or TAA. Otherwise, enable mitigation for VMM only.
+ */
+ if (boot_cpu_has_bug(X86_BUG_MDS) || (boot_cpu_has_bug(X86_BUG_TAA) &&
+ boot_cpu_has(X86_FEATURE_RTM)))
+ static_branch_enable(&mds_user_clear);
+ else
+ static_branch_enable(&mmio_stale_data_clear);
+
+ /*
+ * If Processor-MMIO-Stale-Data bug is present and Fill Buffer data can
+ * be propagated to uncore buffers, clearing the Fill buffers on idle
+ * is required irrespective of SMT state.
+ */
+ if (!(ia32_cap & ARCH_CAP_FBSDP_NO))
+ static_branch_enable(&mds_idle_clear);
+
+ /*
+ * Check if the system has the right microcode.
+ *
+ * CPU Fill buffer clear mitigation is enumerated by either an explicit
+ * FB_CLEAR or by the presence of both MD_CLEAR and L1D_FLUSH on MDS
+ * affected systems.
+ */
+ if ((ia32_cap & ARCH_CAP_FB_CLEAR) ||
+ (boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
+ boot_cpu_has(X86_FEATURE_FLUSH_L1D) &&
+ !(ia32_cap & ARCH_CAP_MDS_NO)))
+ mmio_mitigation = MMIO_MITIGATION_VERW;
+ else
+ mmio_mitigation = MMIO_MITIGATION_UCODE_NEEDED;
+
+ if (mmio_nosmt || cpu_mitigations_auto_nosmt())
+ cpu_smt_disable(false);
+}
+
+static int __init mmio_stale_data_parse_cmdline(char *str)
+{
+ if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
+ return 0;
+
+ if (!str)
+ return -EINVAL;
+
+ if (!strcmp(str, "off")) {
+ mmio_mitigation = MMIO_MITIGATION_OFF;
+ } else if (!strcmp(str, "full")) {
+ mmio_mitigation = MMIO_MITIGATION_VERW;
+ } else if (!strcmp(str, "full,nosmt")) {
+ mmio_mitigation = MMIO_MITIGATION_VERW;
+ mmio_nosmt = true;
+ }
+
+ return 0;
+}
+early_param("mmio_stale_data", mmio_stale_data_parse_cmdline);
+
+#undef pr_fmt
+#define pr_fmt(fmt) "" fmt
+
+static void __init md_clear_update_mitigation(void)
+{
+ if (cpu_mitigations_off())
+ return;
+
+ if (!static_key_enabled(&mds_user_clear))
+ goto out;
+
+ /*
+ * mds_user_clear is now enabled. Update MDS, TAA and MMIO Stale Data
+ * mitigation, if necessary.
+ */
+ if (mds_mitigation == MDS_MITIGATION_OFF &&
+ boot_cpu_has_bug(X86_BUG_MDS)) {
+ mds_mitigation = MDS_MITIGATION_FULL;
+ mds_select_mitigation();
+ }
+ if (taa_mitigation == TAA_MITIGATION_OFF &&
+ boot_cpu_has_bug(X86_BUG_TAA)) {
+ 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 = MMIO_MITIGATION_VERW;
+ mmio_select_mitigation();
+ }
+out:
+ if (boot_cpu_has_bug(X86_BUG_MDS))
+ pr_info("MDS: %s\n", mds_strings[mds_mitigation]);
+ if (boot_cpu_has_bug(X86_BUG_TAA))
+ pr_info("TAA: %s\n", taa_strings[taa_mitigation]);
+ if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
+ pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]);
+}
+
+static void __init md_clear_select_mitigation(void)
+{
+ mds_select_mitigation();
+ taa_select_mitigation();
+ mmio_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.
+ */
+ md_clear_update_mitigation();
+}
+
+#undef pr_fmt
#define pr_fmt(fmt) "SRBDS: " fmt
enum srbds_mitigations {
@@ -478,11 +602,13 @@ static void __init srbds_select_mitigation(void)
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.
+ * Check to see if this is one of the MDS_NO systems supporting TSX that
+ * are only exposed to SRBDS when TSX is enabled or when CPU is affected
+ * by Processor MMIO Stale Data vulnerability.
*/
ia32_cap = x86_read_arch_cap_msr();
- if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM))
+ if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM) &&
+ !boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
srbds_mitigation = SRBDS_MITIGATION_TSX_OFF;
else if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
srbds_mitigation = SRBDS_MITIGATION_HYPERVISOR;
@@ -1116,6 +1242,8 @@ static void update_indir_branch_cond(void)
/* Update the static key controlling the MDS CPU buffer clear in idle */
static void update_mds_branch_idle(void)
{
+ u64 ia32_cap = x86_read_arch_cap_msr();
+
/*
* Enable the idle clearing if SMT is active on CPUs which are
* affected only by MSBDS and not any other MDS variant.
@@ -1127,14 +1255,17 @@ static void update_mds_branch_idle(void)
if (!boot_cpu_has_bug(X86_BUG_MSBDS_ONLY))
return;
- if (sched_smt_active())
+ if (sched_smt_active()) {
static_branch_enable(&mds_idle_clear);
- else
+ } else if (mmio_mitigation == MMIO_MITIGATION_OFF ||
+ (ia32_cap & ARCH_CAP_FBSDP_NO)) {
static_branch_disable(&mds_idle_clear);
+ }
}
#define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"
#define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n"
+#define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n"
void cpu_bugs_smt_update(void)
{
@@ -1179,6 +1310,16 @@ void cpu_bugs_smt_update(void)
break;
}
+ switch (mmio_mitigation) {
+ case MMIO_MITIGATION_VERW:
+ case MMIO_MITIGATION_UCODE_NEEDED:
+ if (sched_smt_active())
+ pr_warn_once(MMIO_MSG_SMT);
+ break;
+ case MMIO_MITIGATION_OFF:
+ break;
+ }
+
mutex_unlock(&spec_ctrl_mutex);
}
@@ -1781,6 +1922,20 @@ static ssize_t tsx_async_abort_show_state(char *buf)
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))
@@ -1881,6 +2036,9 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
case X86_BUG_SRBDS:
return srbds_show_state(buf);
+ case X86_BUG_MMIO_STALE_DATA:
+ return mmio_stale_data_show_state(buf);
+
default:
break;
}
@@ -1932,4 +2090,9 @@ ssize_t cpu_show_srbds(struct device *dev, struct device_attribute *attr, char *
{
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