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-rw-r--r--arch/x86/kernel/cpu/bugs.c92
1 files changed, 87 insertions, 5 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 48d049cd74..01ac18f561 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);
@@ -474,6 +481,57 @@ 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
static void __init md_clear_update_mitigation(void)
@@ -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 @@ out:
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