[Qemu-devel] [PATCH v3 11/12] target-i386: support "invariant tsc" flag

[Eduardo Habkost]

From: Marcelo Tosatti <address@hidden>

Expose "Invariant TSC" flag, if KVM is enabled. From Intel documentation:

17.13.1 Invariant TSC The time stamp counter in newer processors may
support an enhancement, referred to as invariant TSC. Processor’s
support for invariant TSC is indicated by CPUID.80000007H:EDX[8].
The invariant TSC will run at a constant rate in all ACPI P-, C-.
and T-states. This is the architectural behavior moving forward. On
processors with invariant TSC support, the OS may use the TSC for wall
clock timer services (instead of ACPI or HPET timers). TSC reads are
much more efficient and do not incur the overhead associated with a ring
transition or access to a platform resource.

Signed-off-by: Marcelo Tosatti <address@hidden>
[ehabkost: redo feature filtering to use .tcg_features]
Signed-off-by: Eduardo Habkost <address@hidden>
---
 target-i386/cpu.c | 26 ++++++++++++++++++++++++++
 target-i386/cpu.h |  1 +
 2 files changed, 27 insertions(+)

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 198767f..bcd3a43 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -262,6 +262,17 @@ static const char *cpuid_7_0_ebx_feature_name[] = {
     NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
 };
 
+static const char *cpuid_apm_edx_feature_name[] = {
+    NULL, NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL,
+    "invtsc", NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL,
+};
+
 #define I486_FEATURES (CPUID_FP87 | CPUID_VME | CPUID_PSE)
 #define PENTIUM_FEATURES (I486_FEATURES | CPUID_DE | CPUID_TSC | \
           CPUID_MSR | CPUID_MCE | CPUID_CX8 | CPUID_MMX | CPUID_APIC)
@@ -319,6 +330,7 @@ static const char *cpuid_7_0_ebx_feature_name[] = {
           CPUID_7_0_EBX_FSGSBASE, CPUID_7_0_EBX_HLE, CPUID_7_0_EBX_AVX2,
           CPUID_7_0_EBX_ERMS, CPUID_7_0_EBX_INVPCID, CPUID_7_0_EBX_RTM,
           CPUID_7_0_EBX_RDSEED */
+#define TCG_APM_FEATURES 0
 
 
 typedef struct FeatureWordInfo {
@@ -373,6 +385,12 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         .cpuid_reg = R_EBX,
         .tcg_features = TCG_7_0_EBX_FEATURES,
     },
+    [FEAT_8000_0007_EDX] = {
+        .feat_names = cpuid_apm_edx_feature_name,
+        .cpuid_eax = 0x80000007,
+        .cpuid_reg = R_EDX,
+        .tcg_features = TCG_APM_FEATURES,
+    },
 };
 
 typedef struct X86RegisterInfo32 {
@@ -1731,6 +1749,7 @@ static void x86_cpu_parse_featurestr(CPUState *cs, char 
*features,
     env->features[FEAT_1_ECX] |= plus_features[FEAT_1_ECX];
     env->features[FEAT_8000_0001_EDX] |= plus_features[FEAT_8000_0001_EDX];
     env->features[FEAT_8000_0001_ECX] |= plus_features[FEAT_8000_0001_ECX];
+    env->features[FEAT_8000_0007_EDX] |= plus_features[FEAT_8000_0007_EDX];
     env->features[FEAT_C000_0001_EDX] |= plus_features[FEAT_C000_0001_EDX];
     env->features[FEAT_KVM] |= plus_features[FEAT_KVM];
     env->features[FEAT_SVM] |= plus_features[FEAT_SVM];
@@ -1739,6 +1758,7 @@ static void x86_cpu_parse_featurestr(CPUState *cs, char 
*features,
     env->features[FEAT_1_ECX] &= ~minus_features[FEAT_1_ECX];
     env->features[FEAT_8000_0001_EDX] &= ~minus_features[FEAT_8000_0001_EDX];
     env->features[FEAT_8000_0001_ECX] &= ~minus_features[FEAT_8000_0001_ECX];
+    env->features[FEAT_8000_0007_EDX] &= ~minus_features[FEAT_8000_0007_EDX];
     env->features[FEAT_C000_0001_EDX] &= ~minus_features[FEAT_C000_0001_EDX];
     env->features[FEAT_KVM] &= ~minus_features[FEAT_KVM];
     env->features[FEAT_SVM] &= ~minus_features[FEAT_SVM];
@@ -2345,6 +2365,12 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
uint32_t count,
                (AMD_ENC_ASSOC(L3_ASSOCIATIVITY) << 12) | \
                (L3_LINES_PER_TAG << 8) | (L3_LINE_SIZE);
         break;
+    case 0x80000007:
+        *eax = 0;
+        *ebx = 0;
+        *ecx = 0;
+        *edx = env->features[FEAT_8000_0007_EDX];
+        break;
     case 0x80000008:
         /* virtual & phys address size in low 2 bytes. */
 /* XXX: This value must match the one used in the MMU code. */
diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index 2a22a7d..7ad980f 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -398,6 +398,7 @@ typedef enum FeatureWord {
     FEAT_7_0_EBX,       /* CPUID[EAX=7,ECX=0].EBX */
     FEAT_8000_0001_EDX, /* CPUID[8000_0001].EDX */
     FEAT_8000_0001_ECX, /* CPUID[8000_0001].ECX */
+    FEAT_8000_0007_EDX, /* CPUID[8000_0007].EDX */
     FEAT_C000_0001_EDX, /* CPUID[C000_0001].EDX */
     FEAT_KVM,           /* CPUID[4000_0001].EAX (KVM_CPUID_FEATURES) */
     FEAT_SVM,           /* CPUID[8000_000A].EDX */
-- 
1.9.0