Linux-libre 4.7.1-gnupck-4.7.1-gnu

1 files changed, 44 insertions, 7 deletions

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index e4393bfc7..6e2ffbebb 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -25,6 +25,41 @@
 #include <asm/apic.h>
 #endif
 
+/*
+ * Just in case our CPU detection goes bad, or you have a weird system,
+ * allow a way to override the automatic disabling of MPX.
+ */
+static int forcempx;
+
+static int __init forcempx_setup(char *__unused)
+{
+	forcempx = 1;
+
+	return 1;
+}
+__setup("intel-skd-046-workaround=disable", forcempx_setup);
+
+void check_mpx_erratum(struct cpuinfo_x86 *c)
+{
+	if (forcempx)
+		return;
+	/*
+	 * Turn off the MPX feature on CPUs where SMEP is not
+	 * available or disabled.
+	 *
+	 * Works around Intel Erratum SKD046: "Branch Instructions
+	 * May Initialize MPX Bound Registers Incorrectly".
+	 *
+	 * This might falsely disable MPX on systems without
+	 * SMEP, like Atom processors without SMEP.  But there
+	 * is no such hardware known at the moment.
+	 */
+	if (cpu_has(c, X86_FEATURE_MPX) && !cpu_has(c, X86_FEATURE_SMEP)) {
+		setup_clear_cpu_cap(X86_FEATURE_MPX);
+		pr_warn("x86/mpx: Disabling MPX since SMEP not present\n");
+	}
+}
+
 static void early_init_intel(struct cpuinfo_x86 *c)
 {
 	u64 misc_enable;
@@ -152,9 +187,9 @@ static void early_init_intel(struct cpuinfo_x86 *c)
 	 *  the TLB when any changes are made to any of the page table entries.
 	 *  The operating system must reload CR3 to cause the TLB to be flushed"
 	 *
-	 * As a result cpu_has_pge() in arch/x86/include/asm/tlbflush.h should
-	 * be false so that __flush_tlb_all() causes CR3 insted of CR4.PGE
-	 * to be modified
+	 * As a result, boot_cpu_has(X86_FEATURE_PGE) in arch/x86/include/asm/tlbflush.h
+	 * should be false so that __flush_tlb_all() causes CR3 insted of CR4.PGE
+	 * to be modified.
 	 */
 	if (c->x86 == 5 && c->x86_model == 9) {
 		pr_info("Disabling PGE capability bit\n");
@@ -173,6 +208,8 @@ static void early_init_intel(struct cpuinfo_x86 *c)
 		if (edx & (1U << 28))
 			c->x86_coreid_bits = get_count_order((ebx >> 16) & 0xff);
 	}
+
+	check_mpx_erratum(c);
 }
 
 #ifdef CONFIG_X86_32
@@ -233,7 +270,7 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
 	 * The Quark is also family 5, but does not have the same bug.
 	 */
 	clear_cpu_bug(c, X86_BUG_F00F);
-	if (!paravirt_enabled() && c->x86 == 5 && c->x86_model < 9) {
+	if (c->x86 == 5 && c->x86_model < 9) {
 		static int f00f_workaround_enabled;
 
 		set_cpu_bug(c, X86_BUG_F00F);
@@ -281,7 +318,7 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
 	 * integrated APIC (see 11AP erratum in "Pentium Processor
 	 * Specification Update").
 	 */
-	if (cpu_has_apic && (c->x86<<8 | c->x86_model<<4) == 0x520 &&
+	if (boot_cpu_has(X86_FEATURE_APIC) && (c->x86<<8 | c->x86_model<<4) == 0x520 &&
 	    (c->x86_mask < 0x6 || c->x86_mask == 0xb))
 		set_cpu_bug(c, X86_BUG_11AP);
 
@@ -456,7 +493,7 @@ static void init_intel(struct cpuinfo_x86 *c)
 			set_cpu_cap(c, X86_FEATURE_ARCH_PERFMON);
 	}
 
-	if (cpu_has_xmm2)
+	if (cpu_has(c, X86_FEATURE_XMM2))
 		set_cpu_cap(c, X86_FEATURE_LFENCE_RDTSC);
 
 	if (boot_cpu_has(X86_FEATURE_DS)) {
@@ -468,7 +505,7 @@ static void init_intel(struct cpuinfo_x86 *c)
 			set_cpu_cap(c, X86_FEATURE_PEBS);
 	}
 
-	if (c->x86 == 6 && cpu_has_clflush &&
+	if (c->x86 == 6 && boot_cpu_has(X86_FEATURE_CLFLUSH) &&
 	    (c->x86_model == 29 || c->x86_model == 46 || c->x86_model == 47))
 		set_cpu_bug(c, X86_BUG_CLFLUSH_MONITOR);