kvm: i386: halt poll control MSR support

Add support for halt poll control MSR: save/restore, migration
and new feature name.

The purpose of this MSR is to allow the guest to disable
host halt poll.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Message-Id: <20190603230408.GA7938@amt.cnet>
[Do not enable by default, as pointed out by Mark Kanda. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/standard-headers/asm-x86/kvm_para.h

@@ -29,6 +29,7 @@
 #define KVM_FEATURE_PV_TLB_FLUSH	9
 #define KVM_FEATURE_ASYNC_PF_VMEXIT	10
 #define KVM_FEATURE_PV_SEND_IPI	11
+#define KVM_FEATURE_POLL_CONTROL	12
 
 #define KVM_HINTS_REALTIME      0
 
@@ -47,6 +48,7 @@
 #define MSR_KVM_ASYNC_PF_EN 0x4b564d02
 #define MSR_KVM_STEAL_TIME  0x4b564d03
 #define MSR_KVM_PV_EOI_EN      0x4b564d04
+#define MSR_KVM_POLL_CONTROL	0x4b564d05
 
 struct kvm_steal_time {
 	uint64_t steal;

target/i386/cpu.c

@@ -906,7 +906,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
             "kvmclock", "kvm-nopiodelay", "kvm-mmu", "kvmclock",
             "kvm-asyncpf", "kvm-steal-time", "kvm-pv-eoi", "kvm-pv-unhalt",
             NULL, "kvm-pv-tlb-flush", NULL, "kvm-pv-ipi",
-            NULL, NULL, NULL, NULL,
+            "kvm-poll-control", NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,
             "kvmclock-stable-bit", NULL, NULL, NULL,
@@ -5660,6 +5660,8 @@ static void x86_cpu_initfn(Object *obj)
     object_property_add_alias(obj, "kvm_steal_time", obj, "kvm-steal-time", &error_abort);
     object_property_add_alias(obj, "kvm_pv_eoi", obj, "kvm-pv-eoi", &error_abort);
     object_property_add_alias(obj, "kvm_pv_unhalt", obj, "kvm-pv-unhalt", &error_abort);
+    object_property_add_alias(obj, "kvm_poll_control", obj, "kvm-poll-control",
+                              &error_abort);
     object_property_add_alias(obj, "svm_lock", obj, "svm-lock", &error_abort);
     object_property_add_alias(obj, "nrip_save", obj, "nrip-save", &error_abort);
     object_property_add_alias(obj, "tsc_scale", obj, "tsc-scale", &error_abort);

target/i386/cpu.h

@@ -1260,6 +1260,7 @@ typedef struct CPUX86State {
     uint64_t steal_time_msr;
     uint64_t async_pf_en_msr;
     uint64_t pv_eoi_en_msr;
+    uint64_t poll_control_msr;
 
     /* Partition-wide HV MSRs, will be updated only on the first vcpu */
     uint64_t msr_hv_hypercall;

target/i386/kvm.c

@@ -1785,6 +1785,8 @@ void kvm_arch_reset_vcpu(X86CPU *cpu)
 
         hyperv_x86_synic_reset(cpu);
     }
+    /* enabled by default */
+    env->poll_control_msr = 1;
 }
 
 void kvm_arch_do_init_vcpu(X86CPU *cpu)
@@ -2493,6 +2495,11 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
         if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_STEAL_TIME)) {
             kvm_msr_entry_add(cpu, MSR_KVM_STEAL_TIME, env->steal_time_msr);
         }
+
+        if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_POLL_CONTROL)) {
+            kvm_msr_entry_add(cpu, MSR_KVM_POLL_CONTROL, env->poll_control_msr);
+        }
+
         if (has_architectural_pmu_version > 0) {
             if (has_architectural_pmu_version > 1) {
                 /* Stop the counter.  */
@@ -2878,6 +2885,9 @@ static int kvm_get_msrs(X86CPU *cpu)
     if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_STEAL_TIME)) {
         kvm_msr_entry_add(cpu, MSR_KVM_STEAL_TIME, 0);
     }
+    if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_POLL_CONTROL)) {
+        kvm_msr_entry_add(cpu, MSR_KVM_POLL_CONTROL, 1);
+    }
     if (has_architectural_pmu_version > 0) {
         if (has_architectural_pmu_version > 1) {
             kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR_CTRL, 0);
@@ -3112,6 +3122,10 @@ static int kvm_get_msrs(X86CPU *cpu)
         case MSR_KVM_STEAL_TIME:
             env->steal_time_msr = msrs[i].data;
             break;
+        case MSR_KVM_POLL_CONTROL: {
+            env->poll_control_msr = msrs[i].data;
+            break;
+        }
         case MSR_CORE_PERF_FIXED_CTR_CTRL:
             env->msr_fixed_ctr_ctrl = msrs[i].data;
             break;

target/i386/machine.c

@@ -437,6 +437,14 @@ static const VMStateDescription vmstate_exception_info = {
     }
 };
 
+/* Poll control MSR enabled by default */
+static bool poll_control_msr_needed(void *opaque)
+{
+    X86CPU *cpu = opaque;
+
+    return cpu->env.poll_control_msr != 1;
+}
+
 static const VMStateDescription vmstate_steal_time_msr = {
     .name = "cpu/steal_time_msr",
     .version_id = 1,
@@ -470,6 +478,17 @@ static const VMStateDescription vmstate_pv_eoi_msr = {
     }
 };
 
+static const VMStateDescription vmstate_poll_control_msr = {
+    .name = "cpu/poll_control_msr",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = poll_control_msr_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64(env.poll_control_msr, X86CPU),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static bool fpop_ip_dp_needed(void *opaque)
 {
     X86CPU *cpu = opaque;
@@ -1354,6 +1373,7 @@ VMStateDescription vmstate_x86_cpu = {
         &vmstate_async_pf_msr,
         &vmstate_pv_eoi_msr,
         &vmstate_steal_time_msr,
+        &vmstate_poll_control_msr,
         &vmstate_fpop_ip_dp,
         &vmstate_msr_tsc_adjust,
         &vmstate_msr_tscdeadline,