[PATCH 2/2] Implement support for precise TSC migration

[Maxim Levitsky <mlevitsk@redhat.com>]

Currently to enable it, you need to set x-precise-tsc=on
for each vcpu.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 target/i386/cpu.c     |   1 +
 target/i386/cpu.h     |   4 ++
 target/i386/kvm.c     | 141 ++++++++++++++++++++++++++++++++++--------
 target/i386/machine.c |  20 ++++++
 4 files changed, 139 insertions(+), 27 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 5a8c96072e..3c82864930 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -7231,6 +7231,7 @@ static Property x86_cpu_properties[] = {
                      false),
     DEFINE_PROP_BOOL("x-intel-pt-auto-level", X86CPU, intel_pt_auto_level,
                      true),
+    DEFINE_PROP_BOOL("x-precise-tsc", X86CPU, precise_tsc, false),
     DEFINE_PROP_END_OF_LIST()
 };
 
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 88e8586f8f..fd355057b8 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1460,6 +1460,7 @@ typedef struct CPUX86State {
     uint64_t tsc_adjust;
     uint64_t tsc_deadline;
     uint64_t tsc_aux;
+    uint64_t tsc_ns_timestamp;
 
     uint64_t xcr0;
 
@@ -1743,6 +1744,9 @@ struct X86CPU {
     /* Number of physical address bits supported */
     uint32_t phys_bits;
 
+    /* Use KVM_GET_TSC_PRECISE/KVM_SET_TSC_PRECISE to access IA32_TSC */
+    bool precise_tsc;
+
     /* in order to simplify APIC support, we leave this pointer to the
        user */
     struct DeviceState *apic_state;
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index a2934dda02..f0488aa6cc 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -121,6 +121,7 @@ static int has_xsave;
 static int has_xcrs;
 static int has_pit_state2;
 static int has_exception_payload;
+static int has_precise_tsc;
 
 static bool has_msr_mcg_ext_ctl;
 
@@ -196,31 +197,109 @@ static int kvm_get_tsc(CPUState *cs)
 {
     X86CPU *cpu = X86_CPU(cs);
     CPUX86State *env = &cpu->env;
-    struct {
-        struct kvm_msrs info;
-        struct kvm_msr_entry entries[1];
-    } msr_data = {};
     int ret;
 
     if (env->tsc_valid) {
         return 0;
     }
 
-    memset(&msr_data, 0, sizeof(msr_data));
-    msr_data.info.nmsrs = 1;
-    msr_data.entries[0].index = MSR_IA32_TSC;
-    env->tsc_valid = !runstate_is_running();
+    if (cpu->precise_tsc) {
+        struct kvm_tsc_state tsc_state;
 
-    ret = kvm_vcpu_ioctl(CPU(cpu), KVM_GET_MSRS, &msr_data);
-    if (ret < 0) {
-        return ret;
+        ret = kvm_vcpu_ioctl(CPU(cpu), KVM_GET_TSC_STATE, &tsc_state);
+        if (ret < 0) {
+            return ret;
+        }
+
+        env->tsc = tsc_state.tsc;
+        if (tsc_state.flags & KVM_TSC_STATE_TSC_ADJUST_VALID) {
+            env->tsc_adjust = tsc_state.tsc_adjust;
+        }
+        env->tsc_ns_timestamp = tsc_state.nsec;
+
+    } else {
+        struct {
+            struct kvm_msrs info;
+            struct kvm_msr_entry entries[2];
+        } msr_data = {};
+
+        memset(&msr_data, 0, sizeof(msr_data));
+        msr_data.info.nmsrs = 1;
+        msr_data.entries[0].index = MSR_IA32_TSC;
+
+        if (has_msr_tsc_adjust) {
+            msr_data.info.nmsrs++;
+            msr_data.entries[1].index = MSR_TSC_ADJUST;
+        }
+
+        ret = kvm_vcpu_ioctl(CPU(cpu), KVM_GET_MSRS, &msr_data);
+        if (ret < 0) {
+            return ret;
+        }
+
+        assert(ret == msr_data.info.nmsrs);
+
+        env->tsc = msr_data.entries[0].data;
+        if (has_msr_tsc_adjust) {
+            env->tsc_adjust = msr_data.entries[1].data;
+        }
     }
 
-    assert(ret == 1);
-    env->tsc = msr_data.entries[0].data;
+    env->tsc_valid = !runstate_is_running();
     return 0;
 }
 
+static int kvm_set_tsc(CPUState *cs)
+{
+    int ret;
+    X86CPU *cpu = X86_CPU(cs);
+    CPUX86State *env = &cpu->env;
+
+    if (cpu->precise_tsc) {
+        struct kvm_tsc_state tsc_state;
+
+        memset(&tsc_state, 0, sizeof(tsc_state));
+
+        tsc_state.tsc = env->tsc;
+        tsc_state.nsec = env->tsc_ns_timestamp;
+
+        if (has_msr_tsc_adjust) {
+            tsc_state.tsc_adjust = env->tsc_adjust;
+            tsc_state.flags |= KVM_TSC_STATE_TSC_ADJUST_VALID;
+        }
+
+        ret = kvm_vcpu_ioctl(CPU(cpu), KVM_SET_TSC_STATE, &tsc_state);
+        if (ret < 0) {
+            return ret;
+        }
+
+    } else {
+        struct {
+            struct kvm_msrs info;
+            struct kvm_msr_entry entries[2];
+        } msr_data = {};
+
+        memset(&msr_data, 0, sizeof(msr_data));
+        msr_data.info.nmsrs = 1;
+        msr_data.entries[0].index = MSR_IA32_TSC;
+        msr_data.entries[0].data = env->tsc;
+
+        if (has_msr_tsc_adjust) {
+            msr_data.info.nmsrs++;
+            msr_data.entries[1].index = MSR_TSC_ADJUST;
+            msr_data.entries[1].data = env->tsc_adjust;
+        }
+
+        ret = kvm_vcpu_ioctl(CPU(cpu), KVM_SET_MSRS, &msr_data);
+        if (ret < 0) {
+            return ret;
+        }
+
+        assert(ret == msr_data.info.nmsrs);
+    }
+    return ret;
+}
+
 static inline void do_kvm_synchronize_tsc(CPUState *cpu, run_on_cpu_data arg)
 {
     kvm_get_tsc(cpu);
@@ -1780,6 +1859,13 @@ int kvm_arch_init_vcpu(CPUState *cs)
         }
     }
 
+    if (cpu->precise_tsc) {
+        if (!kvm_check_extension(cs->kvm_state, KVM_CAP_PRECISE_TSC)) {
+            error_report("kvm: Precise TSC is not supported by the host's KVM");
+            return -ENOTSUP;
+        }
+    }
+
     if (cpu->vmware_cpuid_freq
         /* Guests depend on 0x40000000 to detect this feature, so only expose
          * it if KVM exposes leaf 0x40000000. (Conflicts with Hyper-V) */
@@ -2196,6 +2282,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         int disable_exits = kvm_check_extension(s, KVM_CAP_X86_DISABLE_EXITS);
         int ret;
 
+
+
 /* Work around for kernel header with a typo. TODO: fix header and drop. */
 #if defined(KVM_X86_DISABLE_EXITS_HTL) && !defined(KVM_X86_DISABLE_EXITS_HLT)
 #define KVM_X86_DISABLE_EXITS_HLT KVM_X86_DISABLE_EXITS_HTL
@@ -2215,6 +2303,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         }
     }
 
+    has_precise_tsc = kvm_check_extension(s, KVM_CAP_PRECISE_TSC);
+
     return 0;
 }
 
@@ -2756,9 +2846,6 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
     if (has_msr_tsc_aux) {
         kvm_msr_entry_add(cpu, MSR_TSC_AUX, env->tsc_aux);
     }
-    if (has_msr_tsc_adjust) {
-        kvm_msr_entry_add(cpu, MSR_TSC_ADJUST, env->tsc_adjust);
-    }
     if (has_msr_misc_enable) {
         kvm_msr_entry_add(cpu, MSR_IA32_MISC_ENABLE,
                           env->msr_ia32_misc_enable);
@@ -2802,7 +2889,6 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
      * for normal writeback. Limit them to reset or full state updates.
      */
     if (level >= KVM_PUT_RESET_STATE) {
-        kvm_msr_entry_add(cpu, MSR_IA32_TSC, env->tsc);
         kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, env->system_time_msr);
         kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
         if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_ASYNC_PF_INT)) {
@@ -3142,9 +3228,6 @@ static int kvm_get_msrs(X86CPU *cpu)
     if (has_msr_tsc_aux) {
         kvm_msr_entry_add(cpu, MSR_TSC_AUX, 0);
     }
-    if (has_msr_tsc_adjust) {
-        kvm_msr_entry_add(cpu, MSR_TSC_ADJUST, 0);
-    }
     if (has_msr_tsc_deadline) {
         kvm_msr_entry_add(cpu, MSR_IA32_TSCDEADLINE, 0);
     }
@@ -3178,10 +3261,6 @@ static int kvm_get_msrs(X86CPU *cpu)
     if (has_msr_virt_ssbd) {
         kvm_msr_entry_add(cpu, MSR_VIRT_SSBD, 0);
     }
-    if (!env->tsc_valid) {
-        kvm_msr_entry_add(cpu, MSR_IA32_TSC, 0);
-        env->tsc_valid = !runstate_is_running();
-    }
 
 #ifdef TARGET_X86_64
     if (lm_capable_kernel) {
@@ -3385,9 +3464,6 @@ static int kvm_get_msrs(X86CPU *cpu)
         case MSR_TSC_AUX:
             env->tsc_aux = msrs[i].data;
             break;
-        case MSR_TSC_ADJUST:
-            env->tsc_adjust = msrs[i].data;
-            break;
         case MSR_IA32_TSCDEADLINE:
             env->tsc_deadline = msrs[i].data;
             break;
@@ -3995,6 +4071,11 @@ int kvm_arch_put_registers(CPUState *cpu, int level)
         if (ret < 0) {
             return ret;
         }
+
+        ret = kvm_set_tsc(cpu);
+        if (ret < 0) {
+            return ret;
+        }
     }
 
     ret = kvm_put_tscdeadline_msr(x86_cpu);
@@ -4064,6 +4145,12 @@ int kvm_arch_get_registers(CPUState *cs)
     if (ret < 0) {
         goto out;
     }
+
+    ret = kvm_get_tsc(cs);
+    if (ret < 0) {
+        goto out;
+    }
+
     ret = 0;
  out:
     cpu_sync_bndcs_hflags(&cpu->env);
diff --git a/target/i386/machine.c b/target/i386/machine.c
index 233e46bb70..4f4296a3e4 100644
--- a/target/i386/machine.c
+++ b/target/i386/machine.c
@@ -1359,6 +1359,25 @@ static const VMStateDescription vmstate_msr_tsx_ctrl = {
     }
 };
 
+
+static bool tsc_info_needed(void *opaque)
+{
+    X86CPU *cpu = opaque;
+    return cpu->precise_tsc;
+}
+
+static const VMStateDescription vmstate_tsc_info = {
+    .name = "cpu/tsc_nsec_info",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = tsc_info_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64(env.tsc_ns_timestamp, X86CPU),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+
 VMStateDescription vmstate_x86_cpu = {
     .name = "cpu",
     .version_id = 12,
@@ -1493,6 +1512,7 @@ VMStateDescription vmstate_x86_cpu = {
 #endif
 #ifdef CONFIG_KVM
         &vmstate_nested_state,
+        &vmstate_tsc_info,
 #endif
         &vmstate_msr_tsx_ctrl,
         NULL
-- 
2.26.2