linux-kernel - [PATCH RFC 7/7] x86: cpu: update blacklist spec features for late loading

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Date:   Thu,  2 Jul 2020 18:18:27 +0300
From:   Mihai Carabas <mihai.carabas@...cle.com>
To:     linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
        Mihai Carabas <mihai.carabas@...cle.com>
Subject: [PATCH RFC 7/7] x86: cpu: update blacklist spec features for late loading

If we have loaded a broken microcode at boot time, all the
speculation features will be blacklisted. Created a new
function for Intel CPUs to verify if we have a broken microcode
loaded or not and whitelist/blacklist features as needed.

This has to be done before get_cpu_cap because it uses these
black/white lists.

Signed-off-by: Mihai Carabas <mihai.carabas@...cle.com>
---
 arch/x86/include/asm/microcode_intel.h |  1 +
 arch/x86/kernel/cpu/intel.c            | 28 ++++++++++++++++++++++++++++
 arch/x86/kernel/cpu/microcode/intel.c  |  5 ++++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/microcode_intel.h b/arch/x86/include/asm/microcode_intel.h
index d85a07d..74c87cc 100644
--- a/arch/x86/include/asm/microcode_intel.h
+++ b/arch/x86/include/asm/microcode_intel.h
@@ -74,6 +74,7 @@ static inline u32 intel_get_microcode_revision(void)
 extern void show_ucode_info_early(void);
 extern int __init save_microcode_in_initrd_intel(void);
 void reload_ucode_intel(void);
+void check_intel_bad_spectre_microcode(struct cpuinfo_x86 *c);
 #else
 static inline __init void load_ucode_intel_bsp(void) {}
 static inline void load_ucode_intel_ap(void) {}
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index c25a67a..286168e 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -170,6 +170,34 @@ static bool bad_spectre_microcode(struct cpuinfo_x86 *c)
 	return false;
 }
 
+/*
+ * check_intel_bad_spectre_microcode verifies if a valid microcode was
+ * loaded and whitelist/blacklist the features related to speculation control.
+ */
+void check_intel_bad_spectre_microcode(struct cpuinfo_x86 *c)
+{
+	int i;
+	unsigned int features[] = {
+		X86_FEATURE_IBRS,
+		X86_FEATURE_IBPB,
+		X86_FEATURE_STIBP,
+		X86_FEATURE_SPEC_CTRL,
+		X86_FEATURE_MSR_SPEC_CTRL,
+		X86_FEATURE_INTEL_STIBP,
+		X86_FEATURE_SSBD,
+		X86_FEATURE_SPEC_CTRL_SSBD
+	};
+
+	if (bad_spectre_microcode(c)) {
+		for (i = 0; i < ARRAY_SIZE(features); i++)
+			set_bit(features[i], (unsigned long *)cpu_caps_cleared);
+	} else {
+		for (i = 0; i < ARRAY_SIZE(features); i++)
+			clear_bit(features[i],
+				  (unsigned long *)cpu_caps_cleared);
+	}
+}
+
 static void early_init_intel(struct cpuinfo_x86 *c)
 {
 	u64 misc_enable;
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 2ef4338..73a5a52 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -854,8 +854,11 @@ static enum ucode_state apply_microcode_intel(int cpu)
 	c->microcode	 = rev;
 
 	/* Update boot_cpu_data's revision too, if we're on the BSP: */
-	if (bsp)
+	if (bsp) {
 		boot_cpu_data.microcode = rev;
+		/* Whitelist/blacklist speculation control features. */
+		check_intel_bad_spectre_microcode(c);
+	}
 
 	return ret;
 }
-- 
1.8.3.1