[PATCH v4 4/6] target/i386: Support full-width writes for perf counters

[Zide Chen <zide.chen@intel.com>]

From: Dapeng Mi <dapeng1.mi@linux.intel.com>

If IA32_PERF_CAPABILITIES.FW_WRITE (bit 13) is set, each general-
purpose counter IA32_PMCi (starting at 0xc1) is accompanied by a
corresponding 64-bit alias MSR starting at 0x4c1 (IA32_A_PMC0).

The legacy IA32_PMCi MSRs are not full-width and their effective width
is determined by CPUID.0AH:EAX[23:16].

Since these MSRs are architectural aliases, when IA32_A_PMCi is
supported it is safe to use it for save/restore instead of the legacy
IA32_PMCi MSRs.

Full-width write is a user-visible feature and can be disabled
individually.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
---
V3:
- Move the MAX_GP_COUNTERS change and migrate version ID code to
  [patch v3 4/13] to avoid bumping version IDs twice in one patch
  series.

V2:
- Slightly improve the commit message wording.
- Update the comment for MSR_IA32_PMC0 definition.
---
 target/i386/cpu.h     |  3 +++
 target/i386/kvm/kvm.c | 18 ++++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 5288c92fe52f..8cc3c2f139e7 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -421,6 +421,7 @@ typedef enum X86Seg {
 
 #define MSR_IA32_PERF_CAPABILITIES      0x345
 #define PERF_CAP_LBR_FMT                0x3f
+#define PERF_CAP_FULL_WRITE             (1U << 13)
 
 #define MSR_IA32_TSX_CTRL		0x122
 #define MSR_IA32_TSCDEADLINE            0x6e0
@@ -448,6 +449,8 @@ typedef enum X86Seg {
 #define MSR_IA32_SGXLEPUBKEYHASH3       0x8f
 
 #define MSR_P6_PERFCTR0                 0xc1
+/* Alias MSR range for full-width general-purpose performance counters */
+#define MSR_IA32_PMC0                   0x4c1
 
 #define MSR_IA32_SMBASE                 0x9e
 #define MSR_SMI_COUNT                   0x34
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 5c953a0f3a60..a99c1dba83f2 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -4270,6 +4270,12 @@ static int kvm_put_msrs(X86CPU *cpu, KvmPutState level)
         }
 
         if ((IS_INTEL_CPU(env) || IS_ZHAOXIN_CPU(env)) && pmu_version > 0) {
+            uint32_t perf_cntr_base = MSR_P6_PERFCTR0;
+
+            if (env->features[FEAT_PERF_CAPABILITIES] & PERF_CAP_FULL_WRITE) {
+                perf_cntr_base = MSR_IA32_PMC0;
+            }
+
             if (pmu_version > 1) {
                 /* Stop the counter.  */
                 kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR_CTRL, 0);
@@ -4282,7 +4288,7 @@ static int kvm_put_msrs(X86CPU *cpu, KvmPutState level)
                                   env->msr_fixed_counters[i]);
             }
             for (i = 0; i < num_pmu_gp_counters; i++) {
-                kvm_msr_entry_add(cpu, MSR_P6_PERFCTR0 + i,
+                kvm_msr_entry_add(cpu, perf_cntr_base + i,
                                   env->msr_gp_counters[i]);
                 kvm_msr_entry_add(cpu, MSR_P6_EVNTSEL0 + i,
                                   env->msr_gp_evtsel[i]);
@@ -4844,6 +4850,11 @@ static int kvm_get_msrs(X86CPU *cpu)
     }
 
     if ((IS_INTEL_CPU(env) || IS_ZHAOXIN_CPU(env)) && pmu_version > 0) {
+        uint32_t perf_cntr_base = MSR_P6_PERFCTR0;
+
+        if (env->features[FEAT_PERF_CAPABILITIES] & PERF_CAP_FULL_WRITE) {
+            perf_cntr_base = MSR_IA32_PMC0;
+        }
         if (pmu_version > 1) {
             kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR_CTRL, 0);
             kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_CTRL, 0);
@@ -4853,7 +4864,7 @@ static int kvm_get_msrs(X86CPU *cpu)
             kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR0 + i, 0);
         }
         for (i = 0; i < num_pmu_gp_counters; i++) {
-            kvm_msr_entry_add(cpu, MSR_P6_PERFCTR0 + i, 0);
+            kvm_msr_entry_add(cpu, perf_cntr_base + i, 0);
             kvm_msr_entry_add(cpu, MSR_P6_EVNTSEL0 + i, 0);
         }
     }
@@ -5218,6 +5229,9 @@ static int kvm_get_msrs(X86CPU *cpu)
         case MSR_P6_PERFCTR0 ... MSR_P6_PERFCTR0 + MAX_GP_COUNTERS - 1:
             env->msr_gp_counters[index - MSR_P6_PERFCTR0] = msrs[i].data;
             break;
+        case MSR_IA32_PMC0 ... MSR_IA32_PMC0 + MAX_GP_COUNTERS - 1:
+            env->msr_gp_counters[index - MSR_IA32_PMC0] = msrs[i].data;
+            break;
         case MSR_P6_EVNTSEL0 ... MSR_P6_EVNTSEL0 + MAX_GP_COUNTERS - 1:
             env->msr_gp_evtsel[index - MSR_P6_EVNTSEL0] = msrs[i].data;
             break;
-- 
2.54.0