x86/bhi: Define SPEC_CTRL_BHI_DIS_S

Newer processors supports a hardware control BHI_DIS_S to mitigate
Branch History Injection (BHI). Setting BHI_DIS_S protects the kernel
from userspace BHI attacks without having to manually overwrite the
branch history.

Define MSR_SPEC_CTRL bit BHI_DIS_S and its enumeration CPUID.BHI_CTRL.
Mitigation is enabled later.

Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 9b94a86..4085090 100644 (file)
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -467,6 +467,7 @@
  */
 #define X86_FEATURE_AMD_LBR_PMC_FREEZE (21*32+ 0) /* AMD LBR and PMC Freeze */
 #define X86_FEATURE_CLEAR_BHB_LOOP     (21*32+ 1) /* "" Clear branch history at syscall entry using SW loop */
+#define X86_FEATURE_BHI_CTRL           (21*32+ 2) /* "" BHI_DIS_S HW control available */
 
 /*
  * BUG word(s)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 05956bd..24615e8 100644 (file)
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -61,10 +61,13 @@
 #define SPEC_CTRL_SSBD                 BIT(SPEC_CTRL_SSBD_SHIFT)       /* Speculative Store Bypass Disable */
 #define SPEC_CTRL_RRSBA_DIS_S_SHIFT    6          /* Disable RRSBA behavior */
 #define SPEC_CTRL_RRSBA_DIS_S          BIT(SPEC_CTRL_RRSBA_DIS_S_SHIFT)
+#define SPEC_CTRL_BHI_DIS_S_SHIFT      10         /* Disable Branch History Injection behavior */
+#define SPEC_CTRL_BHI_DIS_S            BIT(SPEC_CTRL_BHI_DIS_S_SHIFT)
 
 /* A mask for bits which the kernel toggles when controlling mitigations */
 #define SPEC_CTRL_MITIGATIONS_MASK     (SPEC_CTRL_IBRS | SPEC_CTRL_STIBP | SPEC_CTRL_SSBD \
-                                                       | SPEC_CTRL_RRSBA_DIS_S)
+                                                       | SPEC_CTRL_RRSBA_DIS_S \
+                                                       | SPEC_CTRL_BHI_DIS_S)
 
 #define MSR_IA32_PRED_CMD              0x00000049 /* Prediction Command */
 #define PRED_CMD_IBPB                  BIT(0)     /* Indirect Branch Prediction Barrier */

diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index a515328..af5aa2c 100644 (file)
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -28,6 +28,7 @@ static const struct cpuid_bit cpuid_bits[] = {
        { X86_FEATURE_EPB,              CPUID_ECX,  3, 0x00000006, 0 },
        { X86_FEATURE_INTEL_PPIN,       CPUID_EBX,  0, 0x00000007, 1 },
        { X86_FEATURE_RRSBA_CTRL,       CPUID_EDX,  2, 0x00000007, 2 },
+       { X86_FEATURE_BHI_CTRL,         CPUID_EDX,  4, 0x00000007, 2 },
        { X86_FEATURE_CQM_LLC,          CPUID_EDX,  1, 0x0000000f, 0 },
        { X86_FEATURE_CQM_OCCUP_LLC,    CPUID_EDX,  0, 0x0000000f, 1 },
        { X86_FEATURE_CQM_MBM_TOTAL,    CPUID_EDX,  1, 0x0000000f, 1 },

diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index aadefca..da9880d 100644 (file)
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -52,7 +52,7 @@ enum kvm_only_cpuid_leafs {
 #define X86_FEATURE_IPRED_CTRL         KVM_X86_FEATURE(CPUID_7_2_EDX, 1)
 #define KVM_X86_FEATURE_RRSBA_CTRL     KVM_X86_FEATURE(CPUID_7_2_EDX, 2)
 #define X86_FEATURE_DDPD_U             KVM_X86_FEATURE(CPUID_7_2_EDX, 3)
-#define X86_FEATURE_BHI_CTRL           KVM_X86_FEATURE(CPUID_7_2_EDX, 4)
+#define KVM_X86_FEATURE_BHI_CTRL       KVM_X86_FEATURE(CPUID_7_2_EDX, 4)
 #define X86_FEATURE_MCDT_NO            KVM_X86_FEATURE(CPUID_7_2_EDX, 5)
 
 /* CPUID level 0x80000007 (EDX). */
@@ -126,6 +126,7 @@ static __always_inline u32 __feature_translate(int x86_feature)
        KVM_X86_TRANSLATE_FEATURE(CONSTANT_TSC);
        KVM_X86_TRANSLATE_FEATURE(PERFMON_V2);
        KVM_X86_TRANSLATE_FEATURE(RRSBA_CTRL);
+       KVM_X86_TRANSLATE_FEATURE(BHI_CTRL);
        default:
                return x86_feature;
        }