KVM: x86: Reload pit counters for all channels when restoring state

Currently if userspace restores the pit counters with a count of 0
on channels 1 or 2 and the guest attempts to read the count on those
channels, then KVM will perform a mod of 0 and crash.  This will ensure
that 0 values are converted to 65536 as per the spec.

This is CVE-2015-7513.

Signed-off-by: Andy Honig <ahonig@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
void kvm_set_pending_timer(struct kvm_vcpu *vcpu)
{
	/*
	 * Note: KVM_REQ_PENDING_TIMER is implicitly checked in
	 * vcpu_enter_guest.  This function is only called from
	 * the physical CPU that is running vcpu.
	 */
	kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
}

void kvm_set_pending_timer(struct kvm_vcpu *vcpu)
{
	/*
	 * Note: KVM_REQ_PENDING_TIMER is implicitly checked in
	 * vcpu_enter_guest.  This function is only called from
	 * the physical CPU that is running vcpu.
	 */
	kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
}
