KVM: nVMX: Change emulated VMX-preemption timer hrtimer to absolute

Prepare for migration of this hrtimer, by changing it from relative to
absolute. (I couldn't get migration to work with a relative timer.)
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Message-Id: <20200508203643.85477-3-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -2113,7 +2113,8 @@ static void vmx_start_preemption_timer(struct kvm_vcpu *vcpu)
 	preemption_timeout *= 1000000;
 	do_div(preemption_timeout, vcpu->arch.virtual_tsc_khz);
 	hrtimer_start(&vmx->nested.preemption_timer,
-		      ns_to_ktime(preemption_timeout), HRTIMER_MODE_REL_PINNED);
+		      ktime_add_ns(ktime_get(), preemption_timeout),
+		      HRTIMER_MODE_ABS_PINNED);
 }
 
 static u64 nested_vmx_calc_efer(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
@@ -4673,7 +4674,7 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu)
 		goto out_shadow_vmcs;
 
 	hrtimer_init(&vmx->nested.preemption_timer, CLOCK_MONOTONIC,
-		     HRTIMER_MODE_REL_PINNED);
+		     HRTIMER_MODE_ABS_PINNED);
 	vmx->nested.preemption_timer.function = vmx_preemption_timer_fn;
 
 	vmx->nested.vpid02 = allocate_vpid();