2 files changed, 72 insertions, 21 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 519d6f784984..9e6fe391094e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -384,6 +384,9 @@ struct kvm_vcpu_arch {
         u64 last_host_tsc;
         u64 last_guest_tsc;
         u64 last_kernel_ns;
+        u64 last_tsc_nsec;
+        u64 last_tsc_write;
+        bool tsc_catchup;
 
         bool nmi_pending;
         bool nmi_injected;
@@ -444,6 +447,9 @@ struct kvm_arch {
         u64 last_tsc_nsec;
         u64 last_tsc_offset;
         u64 last_tsc_write;
+        u32 virtual_tsc_khz;
+        u32 virtual_tsc_mult;
+        s8 virtual_tsc_shift;
 
         struct kvm_xen_hvm_config xen_hvm_config;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ce57cd899a62..bfcf8fd5e080 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -962,6 +962,7 @@ static inline u64 get_kernel_ns(void)
 }
 
 static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz);
+unsigned long max_tsc_khz;
 
 static inline int kvm_tsc_changes_freq(void)
 {
@@ -985,6 +986,24 @@ static inline u64 nsec_to_cycles(u64 nsec)
         return ret;
 }
 
+static void kvm_arch_set_tsc_khz(struct kvm *kvm, u32 this_tsc_khz)
+{
+        /* Compute a scale to convert nanoseconds in TSC cycles */
+        kvm_get_time_scale(this_tsc_khz, NSEC_PER_SEC / 1000,
+                           &kvm->arch.virtual_tsc_shift,
+                           &kvm->arch.virtual_tsc_mult);
+        kvm->arch.virtual_tsc_khz = this_tsc_khz;
+}
+
+static u64 compute_guest_tsc(struct kvm_vcpu *vcpu, s64 kernel_ns)
+{
+        u64 tsc = pvclock_scale_delta(kernel_ns-vcpu->arch.last_tsc_nsec,
+                                      vcpu->kvm->arch.virtual_tsc_mult,
+                                      vcpu->kvm->arch.virtual_tsc_shift);
+        tsc += vcpu->arch.last_tsc_write;
+        return tsc;
+}
+
 void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)
 {
         struct kvm *kvm = vcpu->kvm;
@@ -1029,6 +1048,8 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)
 
         /* Reset of TSC must disable overshoot protection below */
         vcpu->arch.hv_clock.tsc_timestamp = 0;
+        vcpu->arch.last_tsc_write = data;
+        vcpu->arch.last_tsc_nsec = ns;
 }
 EXPORT_SYMBOL_GPL(kvm_write_tsc);
 
@@ -1041,22 +1062,42 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
         s64 kernel_ns, max_kernel_ns;
         u64 tsc_timestamp;
 
-        if ((!vcpu->time_page))
-                return 0;
-
         /* Keep irq disabled to prevent changes to the clock */
         local_irq_save(flags);
         kvm_get_msr(v, MSR_IA32_TSC, &tsc_timestamp);
         kernel_ns = get_kernel_ns();
         this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
-        local_irq_restore(flags);
 
         if (unlikely(this_tsc_khz == 0)) {
+                local_irq_restore(flags);
                 kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
                 return 1;
         }
 
         /*
+         * We may have to catch up the TSC to match elapsed wall clock
+         * time for two reasons, even if kvmclock is used.
+         *   1) CPU could have been running below the maximum TSC rate
+         *   2) Broken TSC compensation resets the base at each VCPU
+         *      entry to avoid unknown leaps of TSC even when running
+         *      again on the same CPU.  This may cause apparent elapsed
+         *      time to disappear, and the guest to stand still or run
+         *      very slowly.
+         */
+        if (vcpu->tsc_catchup) {
+                u64 tsc = compute_guest_tsc(v, kernel_ns);
+                if (tsc > tsc_timestamp) {
+                        kvm_x86_ops->adjust_tsc_offset(v, tsc - tsc_timestamp);
+                        tsc_timestamp = tsc;
+                }
+        }
+
+        local_irq_restore(flags);
+
+        if (!vcpu->time_page)
+                return 0;
+
+        /*
          * Time as measured by the TSC may go backwards when resetting the base
          * tsc_timestamp.  The reason for this is that the TSC resolution is
          * higher than the resolution of the other clock scales.  Thus, many
@@ -1122,16 +1163,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
         return 0;
 }
 
-static int kvm_request_guest_time_update(struct kvm_vcpu *v)
-{
-        struct kvm_vcpu_arch *vcpu = &v->arch;
-
-        if (!vcpu->time_page)
-                return 0;
-        kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
-        return 1;
-}
-
 static bool msr_mtrr_valid(unsigned msr)
 {
         switch (msr) {
@@ -1455,6 +1486,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
                 }
 
                 vcpu->arch.time = data;
+                kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
 
                 /* we verify if the enable bit is set... */
                 if (!(data & 1))
@@ -1470,8 +1502,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
                         kvm_release_page_clean(vcpu->arch.time_page);
                         vcpu->arch.time_page = NULL;
                 }
-
-                kvm_request_guest_time_update(vcpu);
                 break;
         }
         case MSR_IA32_MCG_CTL:
@@ -2028,9 +2058,13 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
                                 native_read_tsc() - vcpu->arch.last_host_tsc;
                 if (tsc_delta < 0)
                         mark_tsc_unstable("KVM discovered backwards TSC");
-                if (check_tsc_unstable())
+                if (check_tsc_unstable()) {
                         kvm_x86_ops->adjust_tsc_offset(vcpu, -tsc_delta);
-                kvm_migrate_timers(vcpu);
+                        vcpu->arch.tsc_catchup = 1;
+                        kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
+                }
+                if (vcpu->cpu != cpu)
+                        kvm_migrate_timers(vcpu);
                 vcpu->cpu = cpu;
         }
 }
@@ -4461,8 +4495,7 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
                 kvm_for_each_vcpu(i, vcpu, kvm) {
                         if (vcpu->cpu != freq->cpu)
                                 continue;
-                        if (!kvm_request_guest_time_update(vcpu))
-                                continue;
+                        kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
                         if (vcpu->cpu != smp_processor_id())
                                 send_ipi = 1;
                 }
@@ -4517,11 +4550,20 @@ static void kvm_timer_init(void)
 {
         int cpu;
 
+        max_tsc_khz = tsc_khz;
         register_hotcpu_notifier(&kvmclock_cpu_notifier_block);
         if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
+#ifdef CONFIG_CPU_FREQ
+                struct cpufreq_policy policy;
+                memset(&policy, 0, sizeof(policy));
+                cpufreq_get_policy(&policy, get_cpu());
+                if (policy.cpuinfo.max_freq)
+                        max_tsc_khz = policy.cpuinfo.max_freq;
+#endif
                 cpufreq_register_notifier(&kvmclock_cpufreq_notifier_block,
                                           CPUFREQ_TRANSITION_NOTIFIER);
         }
+        pr_debug("kvm: max_tsc_khz = %ld\n", max_tsc_khz);
         for_each_online_cpu(cpu)
                 smp_call_function_single(cpu, tsc_khz_changed, NULL, 1);
 }
@@ -5752,7 +5794,7 @@ int kvm_arch_hardware_enable(void *garbage)
         list_for_each_entry(kvm, &vm_list, vm_list)
                 kvm_for_each_vcpu(i, vcpu, kvm)
                         if (vcpu->cpu == smp_processor_id())
-                                kvm_request_guest_time_update(vcpu);
+                                kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
         return kvm_x86_ops->hardware_enable(garbage);
 }
 
@@ -5803,6 +5845,9 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
         }
         vcpu->arch.pio_data = page_address(page);
 
+        if (!kvm->arch.virtual_tsc_khz)
+                kvm_arch_set_tsc_khz(kvm, max_tsc_khz);
+
         r = kvm_mmu_create(vcpu);
         if (r < 0)
                 goto fail_free_pio_data;