diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index ab18de894e..339881b40f 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1415,6 +1415,22 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         .tcg_features = 0,
         .unmigratable_flags = 0,
     },
+    [FEAT_8000_0021_ECX] = {
+        .type = CPUID_FEATURE_WORD,
+        .feat_names = {
+            NULL, "tsa-sq-no", "tsa-l1-no", NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+        },
+        .cpuid = { .eax = 0x80000021, .reg = R_ECX, },
+        .tcg_features = 0,
+        .unmigratable_flags = 0,
+    },
     [FEAT_8000_0022_EAX] = {
         .type = CPUID_FEATURE_WORD,
         .feat_names = {
@@ -8526,6 +8542,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         *eax = *ebx = *ecx = *edx = 0;
         *eax = env->features[FEAT_8000_0021_EAX];
         *ebx = env->features[FEAT_8000_0021_EBX];
+        *ecx = env->features[FEAT_8000_0021_ECX];
         break;
     case 0x80000022:
         *eax = *ebx = *ecx = *edx = 0;
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 8b7c173838..f74f13534e 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -643,6 +643,7 @@ typedef enum FeatureWord {
     FEAT_8000_0008_EBX, /* CPUID[8000_0008].EBX */
     FEAT_8000_0021_EAX, /* CPUID[8000_0021].EAX */
     FEAT_8000_0021_EBX, /* CPUID[8000_0021].EBX */
+    FEAT_8000_0021_ECX, /* CPUID[8000_0021].ECX */
     FEAT_8000_0022_EAX, /* CPUID[8000_0022].EAX */
     FEAT_C000_0001_EDX, /* CPUID[C000_0001].EDX */
     FEAT_KVM,           /* CPUID[4000_0001].EAX (KVM_CPUID_FEATURES) */
@@ -1126,6 +1127,11 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w);
  */
 #define CPUID_8000_0021_EBX_RAPSIZE    (8U << 16)
 
+/* CPU is not vulnerable TSA SA-SQ attack */
+#define CPUID_8000_0021_ECX_TSA_SQ_NO  (1U << 1)
+/* CPU is not vulnerable TSA SA-L1 attack */
+#define CPUID_8000_0021_ECX_TSA_L1_NO  (1U << 2)
+
 /* Performance Monitoring Version 2 */
 #define CPUID_8000_0022_EAX_PERFMON_V2  (1U << 0)