Register a notifier for clocksource change event. In case
the host switches to clock other than TSC, disable master
clock usage.
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Index: vsyscall/arch/x86/kvm/x86.c
===================================================================
--- vsyscall.orig/arch/x86/kvm/x86.c
+++ vsyscall/arch/x86/kvm/x86.c
@@ -1218,6 +1218,7 @@ static bool kvm_get_time_and_clockread(s
return true;
}
+static atomic_t kvm_guest_has_master_clock = ATOMIC_INIT(0);
/*
*
@@ -1271,6 +1272,8 @@ static void pvclock_update_vm_gtod_copy(
ka->use_master_clock = kvm_get_time_and_clockread(
&ka->master_kernel_ns,
&ka->master_cycle_now);
+ if (ka->use_master_clock)
+ atomic_set(&kvm_guest_has_master_clock, 1);
vclock_mode = pvclock_gtod_data.clock.vclock_mode;
trace_kvm_update_master_clock(ka->use_master_clock, vclock_mode);
@@ -5124,6 +5127,44 @@ static void kvm_set_mmio_spte_mask(void)
kvm_mmu_set_mmio_spte_mask(mask);
}
+static void pvclock_gtod_update_fn(struct work_struct *work)
+{
+ struct kvm *kvm;
+ struct kvm_vcpu *vcpu;
+ int i;
+
+ raw_spin_lock(&kvm_lock);
+ list_for_each_entry(kvm, &vm_list, vm_list)
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ set_bit(KVM_REQ_MASTERCLOCK_UPDATE, &vcpu->requests);
+ atomic_set(&kvm_guest_has_master_clock, 0);
+ raw_spin_unlock(&kvm_lock);
+}
+
+static DECLARE_WORK(pvclock_gtod_work, pvclock_gtod_update_fn);
+
+/*
+ * Notification about pvclock gtod data update.
+ */
+static int pvclock_gtod_notify(struct notifier_block *nb, unsigned long unused,
+ void *unused2)
+{
+ struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
+
+ /* disable master clock if host does not trust, or does not
+ * use, TSC clocksource
+ */
+ if (gtod->clock.vclock_mode != VCLOCK_TSC &&
+ atomic_read(&kvm_guest_has_master_clock) != 0)
+ queue_work(system_long_wq, &pvclock_gtod_work);
+
+ return 0;
+}
+
+static struct notifier_block pvclock_gtod_notifier = {
+ .notifier_call = pvclock_gtod_notify,
+};
+
int kvm_arch_init(void *opaque)
{
int r;
@@ -5165,6 +5206,8 @@ int kvm_arch_init(void *opaque)
host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
kvm_lapic_init();
+ pvclock_gtod_register_notifier(&pvclock_gtod_notifier);
+
return 0;
out:
@@ -5179,6 +5222,7 @@ void kvm_arch_exit(void)
cpufreq_unregister_notifier(&kvmclock_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
unregister_hotcpu_notifier(&kvmclock_cpu_notifier_block);
+ pvclock_gtod_unregister_notifier(&pvclock_gtod_notifier);
kvm_x86_ops = NULL;
kvm_mmu_module_exit();
}
--
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