The offset to add to the hosts monotonic time, kvmclock_offset, is
calculated against the monotonic time at KVM_SET_CLOCK ioctl time.
Request a master clock update at this time, to reduce a potentially
unbounded difference between the values of the masterclock and
the clock value used to calculate kvmclock_offset.
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d21bce5..0a93354 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1457,6 +1457,29 @@ static void pvclock_update_vm_gtod_copy(struct kvm *kvm)
#endif
}
+static void kvm_gen_update_masterclock(struct kvm *kvm)
+{
+#ifdef CONFIG_X86_64
+ int i;
+ struct kvm_vcpu *vcpu;
+ struct kvm_arch *ka = &kvm->arch;
+
+ spin_lock(&ka->pvclock_gtod_sync_lock);
+ kvm_make_mclock_inprogress_request(kvm);
+ /* no guest entries from this point */
+ pvclock_update_vm_gtod_copy(kvm);
+
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ set_bit(KVM_REQ_CLOCK_UPDATE, &vcpu->requests);
+
+ /* guest entries allowed */
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ clear_bit(KVM_REQ_MCLOCK_INPROGRESS, &vcpu->requests);
+
+ spin_unlock(&ka->pvclock_gtod_sync_lock);
+#endif
+}
+
static int kvm_guest_time_update(struct kvm_vcpu *v)
{
unsigned long flags, this_tsc_khz;
@@ -3806,6 +3829,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
delta = user_ns.clock - now_ns;
local_irq_enable();
kvm->arch.kvmclock_offset = delta;
+ kvm_gen_update_masterclock(kvm);
break;
}
case KVM_GET_CLOCK: {
@@ -5689,29 +5713,6 @@ static void process_nmi(struct kvm_vcpu *vcpu)
kvm_make_request(KVM_REQ_EVENT, vcpu);
}
-static void kvm_gen_update_masterclock(struct kvm *kvm)
-{
-#ifdef CONFIG_X86_64
- int i;
- struct kvm_vcpu *vcpu;
- struct kvm_arch *ka = &kvm->arch;
-
- spin_lock(&ka->pvclock_gtod_sync_lock);
- kvm_make_mclock_inprogress_request(kvm);
- /* no guest entries from this point */
- pvclock_update_vm_gtod_copy(kvm);
-
- kvm_for_each_vcpu(i, vcpu, kvm)
- set_bit(KVM_REQ_CLOCK_UPDATE, &vcpu->requests);
-
- /* guest entries allowed */
- kvm_for_each_vcpu(i, vcpu, kvm)
- clear_bit(KVM_REQ_MCLOCK_INPROGRESS, &vcpu->requests);
-
- spin_unlock(&ka->pvclock_gtod_sync_lock);
-#endif
-}
-
static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
{
u64 eoi_exit_bitmap[4];
--
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