[PATCH v4 1/6] target/i386: Don't save/restore PERF_GLOBAL_OVF_CTRL MSRs

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

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

MSR_CORE_PERF_GLOBAL_OVF_CTRL and MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_CLR
are write-only MSRs and reads always return zero.

Saving and restoring these MSRs is therefore unnecessary.  Replace
VMSTATE_UINT64 with VMSTATE_UNUSED in the VMStateDescription to ignore
env.msr_global_ovf_ctrl during migration.  This avoids the need to bump
version_id and does not introduce any migration incompatibility.

Cc: Dongli Zhang <dongli.zhang@oracle.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Fixes: e587632c228e ("target/i386/kvm: support perfmon-v2 for reset")
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Co-developed-by: Zide Chen <zide.chen@intel.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
---
V3:
- Remove MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_CLR as well.
---
 target/i386/cpu.h     |  3 ---
 target/i386/kvm/kvm.c | 10 ----------
 target/i386/machine.c |  4 ++--
 3 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 6b500737c3be..ff44487d0b6d 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -507,11 +507,9 @@ typedef enum X86Seg {
 #define MSR_CORE_PERF_FIXED_CTR_CTRL    0x38d
 #define MSR_CORE_PERF_GLOBAL_STATUS     0x38e
 #define MSR_CORE_PERF_GLOBAL_CTRL       0x38f
-#define MSR_CORE_PERF_GLOBAL_OVF_CTRL   0x390
 
 #define MSR_AMD64_PERF_CNTR_GLOBAL_STATUS       0xc0000300
 #define MSR_AMD64_PERF_CNTR_GLOBAL_CTL          0xc0000301
-#define MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_CLR   0xc0000302
 
 #define MSR_K7_EVNTSEL0                 0xc0010000
 #define MSR_K7_PERFCTR0                 0xc0010004
@@ -2104,7 +2102,6 @@ typedef struct CPUArchState {
     uint64_t msr_fixed_ctr_ctrl;
     uint64_t msr_global_ctrl;
     uint64_t msr_global_status;
-    uint64_t msr_global_ovf_ctrl;
     uint64_t msr_fixed_counters[MAX_FIXED_COUNTERS];
     uint64_t msr_gp_counters[MAX_GP_COUNTERS];
     uint64_t msr_gp_evtsel[MAX_GP_COUNTERS];
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index a29f757c168a..1ac1803e8a2e 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -4290,8 +4290,6 @@ static int kvm_put_msrs(X86CPU *cpu, KvmPutState level)
             if (pmu_version > 1) {
                 kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_STATUS,
                                   env->msr_global_status);
-                kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_OVF_CTRL,
-                                  env->msr_global_ovf_ctrl);
 
                 /* Now start the PMU.  */
                 kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR_CTRL,
@@ -4335,8 +4333,6 @@ static int kvm_put_msrs(X86CPU *cpu, KvmPutState level)
             if (pmu_version > 1) {
                 kvm_msr_entry_add(cpu, MSR_AMD64_PERF_CNTR_GLOBAL_STATUS,
                                   env->msr_global_status);
-                kvm_msr_entry_add(cpu, MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_CLR,
-                                  env->msr_global_ovf_ctrl);
                 kvm_msr_entry_add(cpu, MSR_AMD64_PERF_CNTR_GLOBAL_CTL,
                                   env->msr_global_ctrl);
             }
@@ -4852,7 +4848,6 @@ static int kvm_get_msrs(X86CPU *cpu)
             kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR_CTRL, 0);
             kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_CTRL, 0);
             kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_STATUS, 0);
-            kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_OVF_CTRL, 0);
         }
         for (i = 0; i < num_pmu_fixed_counters; i++) {
             kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR0 + i, 0);
@@ -4895,7 +4890,6 @@ static int kvm_get_msrs(X86CPU *cpu)
         if (pmu_version > 1) {
             kvm_msr_entry_add(cpu, MSR_AMD64_PERF_CNTR_GLOBAL_CTL, 0);
             kvm_msr_entry_add(cpu, MSR_AMD64_PERF_CNTR_GLOBAL_STATUS, 0);
-            kvm_msr_entry_add(cpu, MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_CLR, 0);
         }
     }
 
@@ -5218,10 +5212,6 @@ static int kvm_get_msrs(X86CPU *cpu)
         case MSR_AMD64_PERF_CNTR_GLOBAL_STATUS:
             env->msr_global_status = msrs[i].data;
             break;
-        case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
-        case MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_CLR:
-            env->msr_global_ovf_ctrl = msrs[i].data;
-            break;
         case MSR_CORE_PERF_FIXED_CTR0 ... MSR_CORE_PERF_FIXED_CTR0 + MAX_FIXED_COUNTERS - 1:
             env->msr_fixed_counters[index - MSR_CORE_PERF_FIXED_CTR0] = msrs[i].data;
             break;
diff --git a/target/i386/machine.c b/target/i386/machine.c
index 48a2a4b31907..e0a5a5da6f5a 100644
--- a/target/i386/machine.c
+++ b/target/i386/machine.c
@@ -666,7 +666,7 @@ static bool pmu_enable_needed(void *opaque)
     int i;
 
     if (env->msr_fixed_ctr_ctrl || env->msr_global_ctrl ||
-        env->msr_global_status || env->msr_global_ovf_ctrl) {
+        env->msr_global_status) {
         return true;
     }
     for (i = 0; i < MAX_FIXED_COUNTERS; i++) {
@@ -692,7 +692,7 @@ static const VMStateDescription vmstate_msr_architectural_pmu = {
         VMSTATE_UINT64(env.msr_fixed_ctr_ctrl, X86CPU),
         VMSTATE_UINT64(env.msr_global_ctrl, X86CPU),
         VMSTATE_UINT64(env.msr_global_status, X86CPU),
-        VMSTATE_UINT64(env.msr_global_ovf_ctrl, X86CPU),
+        VMSTATE_UNUSED(sizeof(uint64_t)),
         VMSTATE_UINT64_ARRAY(env.msr_fixed_counters, X86CPU, MAX_FIXED_COUNTERS),
         VMSTATE_UINT64_ARRAY(env.msr_gp_counters, X86CPU, MAX_GP_COUNTERS),
         VMSTATE_UINT64_ARRAY(env.msr_gp_evtsel, X86CPU, MAX_GP_COUNTERS),
-- 
2.54.0