[3/7] target/i386/kvm: init PMU information only once

Commit Message

Dongli Zhang Nov. 4, 2024, 9:40 a.m. UTC

Currently, the 'has_architectural_pmu_version',
'num_architectural_pmu_gp_counters', and
'num_architectural_pmu_fixed_counters' are shared globally across all vCPUs
and are initialized during the setup of each vCPU.

To optimize, initialize PMU information only once for the first vCPU.

Additionally, the code extracted from kvm_x86_build_cpuid() is unrelated to
the process of building the CPUID.

Signed-off-by: Dongli Zhang <[e-mail]>
---
 target/i386/kvm/kvm.c | 71 +++++++++++++++++++++++++++----------------
 1 file changed, 44 insertions(+), 27 deletions(-)

Patch

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index ed73b1e7e0..5c0276f889 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1961,33 +1961,6 @@  static uint32_t kvm_x86_build_cpuid(CPUX86State *env,
         }
     }
 
-    if (limit >= 0x0a) {
-        uint32_t eax, edx;
-
-        cpu_x86_cpuid(env, 0x0a, 0, &eax, &unused, &unused, &edx);
-
-        has_architectural_pmu_version = eax & 0xff;
-        if (has_architectural_pmu_version > 0) {
-            num_architectural_pmu_gp_counters = (eax & 0xff00) >> 8;
-
-            /* Shouldn't be more than 32, since that's the number of bits
-             * available in EBX to tell us _which_ counters are available.
-             * Play it safe.
-             */
-            if (num_architectural_pmu_gp_counters > MAX_GP_COUNTERS) {
-                num_architectural_pmu_gp_counters = MAX_GP_COUNTERS;
-            }
-
-            if (has_architectural_pmu_version > 1) {
-                num_architectural_pmu_fixed_counters = edx & 0x1f;
-
-                if (num_architectural_pmu_fixed_counters > MAX_FIXED_COUNTERS) {
-                    num_architectural_pmu_fixed_counters = MAX_FIXED_COUNTERS;
-                }
-            }
-        }
-    }
-
     cpu_x86_cpuid(env, 0x80000000, 0, &limit, &unused, &unused, &unused);
 
     for (i = 0x80000000; i <= limit; i++) {
@@ -2055,6 +2028,43 @@  full:
     abort();
 }
 
+static void kvm_init_pmu_info(CPUX86State *env)
+{
+    uint32_t eax, edx;
+    uint32_t unused;
+    uint32_t limit;
+
+    cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
+
+    if (limit < 0x0a) {
+        return;
+    }
+
+    cpu_x86_cpuid(env, 0x0a, 0, &eax, &unused, &unused, &edx);
+
+    has_architectural_pmu_version = eax & 0xff;
+    if (has_architectural_pmu_version > 0) {
+        num_architectural_pmu_gp_counters = (eax & 0xff00) >> 8;
+
+        /*
+         * Shouldn't be more than 32, since that's the number of bits
+         * available in EBX to tell us _which_ counters are available.
+         * Play it safe.
+         */
+        if (num_architectural_pmu_gp_counters > MAX_GP_COUNTERS) {
+            num_architectural_pmu_gp_counters = MAX_GP_COUNTERS;
+        }
+
+        if (has_architectural_pmu_version > 1) {
+            num_architectural_pmu_fixed_counters = edx & 0x1f;
+
+            if (num_architectural_pmu_fixed_counters > MAX_FIXED_COUNTERS) {
+                num_architectural_pmu_fixed_counters = MAX_FIXED_COUNTERS;
+            }
+        }
+    }
+}
+
 int kvm_arch_init_vcpu(CPUState *cs)
 {
     struct {
@@ -2237,6 +2247,13 @@  int kvm_arch_init_vcpu(CPUState *cs)
     cpuid_i = kvm_x86_build_cpuid(env, cpuid_data.entries, cpuid_i);
     cpuid_data.cpuid.nent = cpuid_i;
 
+    /*
+     * Initialize PMU information only once for the first vCPU.
+     */
+    if (cs == first_cpu) {
+        kvm_init_pmu_info(env);
+    }
+
     if (((env->cpuid_version >> 8)&0xF) >= 6
         && (env->features[FEAT_1_EDX] & (CPUID_MCE | CPUID_MCA)) ==
            (CPUID_MCE | CPUID_MCA)) {