[PATCH 4/5] target/i386: Add feature bits for CPUID_Fn80000021_EAX

[Babu Moger]

Add the following feature bits.
no-nested-data-bp         : Processor ignores nested data breakpoints.
lfence-always-serializing : LFENCE instruction is always serializing.
null-select-clears-base   : Null Selector Clears Base. When this bit is
                            set, a null segment load clears the segment base.

The documentation for the features are available in the links below.
a. Processor Programming Reference (PPR) for AMD Family 19h Model 01h,
   Revision B1 Processors
b. AMD64 Architecture Programmer’s Manual Volumes 1–5 Publication No. Revision
    40332 4.05 Date October 2022

Link: https://www.amd.com/system/files/TechDocs/55898_B1_pub_0.50.zip
Link: https://www.amd.com/system/files/TechDocs/40332_4.05.pdf

Signed-off-by: Babu Moger <babu.moger@amd.com>
---
 target/i386/cpu.c |   24 ++++++++++++++++++++++++
 target/i386/cpu.h |    8 ++++++++
 2 files changed, 32 insertions(+)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index b20e422b2e..e9175da92f 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -918,6 +918,22 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         .tcg_features = 0,
         .unmigratable_flags = 0,
     },
+    [FEAT_8000_0021_EAX] = {
+        .type = CPUID_FEATURE_WORD,
+        .feat_names = {
+            "no-nested-data-bp", NULL, "lfence-always-serializing", NULL,
+            NULL, NULL, "null-select-clears-base", 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_EAX, },
+        .tcg_features = 0,
+        .unmigratable_flags = 0,
+    },
     [FEAT_XSAVE] = {
         .type = CPUID_FEATURE_WORD,
         .feat_names = {
@@ -6002,6 +6018,10 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
uint32_t count,
             *ebx |= sev_get_reduced_phys_bits() << 6;
         }
         break;
+    case 0x80000021:
+        *eax = env->features[FEAT_8000_0021_EAX];
+        *ebx = *ecx = *edx = 0;
+        break;
     default:
         /* reserved values: zero */
         *eax = 0;
@@ -6429,6 +6449,10 @@ void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
             x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000001F);
         }
 
+        if (env->features[FEAT_8000_0021_EAX]) {
+            x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x80000021);
+        }
+
         /* SGX requires CPUID[0x12] for EPC enumeration */
         if (env->features[FEAT_7_0_EBX] & CPUID_7_0_EBX_SGX) {
             x86_cpu_adjust_level(cpu, &env->cpuid_min_level, 0x12);
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 8c65c92131..42b347051a 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -597,6 +597,7 @@ typedef enum FeatureWord {
     FEAT_8000_0001_ECX, /* CPUID[8000_0001].ECX */
     FEAT_8000_0007_EDX, /* CPUID[8000_0007].EDX */
     FEAT_8000_0008_EBX, /* CPUID[8000_0008].EBX */
+    FEAT_8000_0021_EAX, /* CPUID[8000_0021].EAX */
     FEAT_C000_0001_EDX, /* CPUID[C000_0001].EDX */
     FEAT_KVM,           /* CPUID[4000_0001].EAX (KVM_CPUID_FEATURES) */
     FEAT_KVM_HINTS,     /* CPUID[4000_0001].EDX */
@@ -925,6 +926,13 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
 /* Predictive Store Forwarding Disable */
 #define CPUID_8000_0008_EBX_AMD_PSFD    (1U << 28)
 
+/* Processor ignores nested data breakpoints */
+#define CPUID_8000_0021_EAX_No_NESTED_DATA_BP    (1U << 0)
+/* LFENCE is always serializing */
+#define CPUID_8000_0021_EAX_LFENCE_ALWAYS_SERIALIZING    (1U << 2)
+/* Null Selector Clears Base */
+#define CPUID_8000_0021_EAX_NULL_SELECT_CLEARS_BASE    (1U << 6)
+
 #define CPUID_XSAVE_XSAVEOPT   (1U << 0)
 #define CPUID_XSAVE_XSAVEC     (1U << 1)
 #define CPUID_XSAVE_XGETBV1    (1U << 2)