diff mbox series

[06/13] KVM: x86: Advertise CPUID.(EAX=7, ECX=2):EDX[5:0] to userspace

Message ID 20240412192351.89501-7-yuxuan.luo@canonical.com
State New
Headers show
Series CVE-2024-2201 | expand

Commit Message

Yuxuan Luo April 12, 2024, 7:23 p.m. UTC 
From: Jim Mattson <jmattson@google.com>

The low five bits {INTEL_PSFD, IPRED_CTRL, RRSBA_CTRL, DDPD_U, BHI_CTRL}
advertise the availability of specific bits in IA32_SPEC_CTRL. Since KVM
dynamically determines the legal IA32_SPEC_CTRL bits for the underlying
hardware, the hard work has already been done. Just let userspace know
that a guest can use these IA32_SPEC_CTRL bits.

The sixth bit (MCDT_NO) states that the processor does not exhibit MXCSR
Configuration Dependent Timing (MCDT) behavior. This is an inherent
property of the physical processor that is inherited by the virtual
CPU. Pass that information on to userspace.

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Link: https://lore.kernel.org/r/20231024001636.890236-1-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
(backported from commit eefe5e6682099445f77f2d97d4c525f9ac9d9b07)
[yuxuan.luo: ignored contextual conflicts]
CVE-2024-2201
Signed-off-by: Yuxuan Luo <yuxuan.luo@canonical.com>
---
 arch/x86/kvm/cpuid.c         | 21 ++++++++++++++++++---
 arch/x86/kvm/reverse_cpuid.h | 12 ++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e4783abc12012..537e826205cec 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -469,6 +469,11 @@  void kvm_set_cpu_caps(void)
 		F(AVX_VNNI) | F(AVX512_BF16)
 	);
 
+	kvm_cpu_cap_init_kvm_defined(CPUID_7_2_EDX,
+		F(INTEL_PSFD) | F(IPRED_CTRL) | F(RRSBA_CTRL) | F(DDPD_U) |
+		F(BHI_CTRL) | F(MCDT_NO)
+	);
+
 	kvm_cpu_cap_mask(CPUID_D_1_EAX,
 		F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | F(XSAVES)
 	);
@@ -710,13 +715,13 @@  static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		break;
 	/* function 7 has additional index. */
 	case 7:
-		entry->eax = min(entry->eax, 1u);
+		max_idx = entry->eax = min(entry->eax, 2u);
 		cpuid_entry_override(entry, CPUID_7_0_EBX);
 		cpuid_entry_override(entry, CPUID_7_ECX);
 		cpuid_entry_override(entry, CPUID_7_EDX);
 
-		/* KVM only supports 0x7.0 and 0x7.1, capped above via min(). */
-		if (entry->eax == 1) {
+		/* KVM only supports up to 0x7.2, capped above via min(). */
+		if (max_idx >= 1) {
 			entry = do_host_cpuid(array, function, 1);
 			if (!entry)
 				goto out;
@@ -726,6 +731,16 @@  static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 			entry->ecx = 0;
 			entry->edx = 0;
 		}
+		if (max_idx >= 2) {
+			entry = do_host_cpuid(array, function, 2);
+			if (!entry)
+				goto out;
+
+			cpuid_entry_override(entry, CPUID_7_2_EDX);
+			entry->ecx = 0;
+			entry->ebx = 0;
+			entry->eax = 0;
+		}
 		break;
 	case 0xa: { /* Architectural Performance Monitoring */
 		struct x86_pmu_capability cap;
diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index 9b73fb8b87d99..d50b653cb8d09 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -13,6 +13,7 @@ 
  */
 enum kvm_only_cpuid_leafs {
 	CPUID_12_EAX	 = NCAPINTS,
+	CPUID_7_2_EDX,
 	NR_KVM_CPU_CAPS,
 
 	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
@@ -36,6 +37,14 @@  enum kvm_only_cpuid_leafs {
 #define KVM_X86_FEATURE_SGX1		KVM_X86_FEATURE(CPUID_12_EAX, 0)
 #define KVM_X86_FEATURE_SGX2		KVM_X86_FEATURE(CPUID_12_EAX, 1)
 
+/* Intel-defined sub-features, CPUID level 0x00000007:2 (EDX) */
+#define X86_FEATURE_INTEL_PSFD		KVM_X86_FEATURE(CPUID_7_2_EDX, 0)
+#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 X86_FEATURE_MCDT_NO		KVM_X86_FEATURE(CPUID_7_2_EDX, 5)
+
 struct cpuid_reg {
 	u32 function;
 	u32 index;
@@ -61,6 +70,7 @@  static const struct cpuid_reg reverse_cpuid[] = {
 	[CPUID_12_EAX]        = {0x00000012, 0, CPUID_EAX},
 	[CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
 	[CPUID_8000_0021_EAX] = {0x80000021, 0, CPUID_EAX},
+	[CPUID_7_2_EDX]       = {         7, 2, CPUID_EDX},
 };
 
 /*
@@ -91,6 +101,8 @@  static __always_inline u32 __feature_translate(int x86_feature)
 		return KVM_X86_FEATURE_SGX1;
 	else if (x86_feature == X86_FEATURE_SGX2)
 		return KVM_X86_FEATURE_SGX2;
+	else if (x86_feature == X86_FEATURE_RRSBA_CTRL)
+		return KVM_X86_FEATURE_RRSBA_CTRL;
 
 	return x86_feature;
 }