void p2m_mem_paging_populate(struct p2m_domain *p2m, unsigned long gfn)
{
    struct vcpu *v = current;
    mem_event_request_t req;
    p2m_type_t p2mt;
    struct domain *d = p2m->domain;

 +  p2m_lock(p2m);
    /* Check that there's space on the ring for this request */
    if ( mem_event_check_ring(d) )
+  {
+     p2m_unlock(p2m);
        return;
+ }

    memset(&req, 0, sizeof(req));
    req.type = MEM_EVENT_TYPE_PAGING;

    /* Fix p2m mapping */
    /* XXX: It seems inefficient to have this here, as it's only needed
     *      in one case (ept guest accessing paging out page) */
    gfn_to_mfn(p2m, gfn, &p2mt);
    if ( p2mt == p2m_ram_paged )
    {
-      p2m_lock(p2m);
        set_p2m_entry(p2m, gfn, _mfn(PAGING_MFN), 0, p2m_ram_paging_in_start, p2m->default_access);
        audit_p2m(p2m, 1);
-     p2m_unlock(p2m);
    }

    /* Pause domain */
    if ( v->domain->domain_id == d->domain_id )
    {
        vcpu_pause_nosync(v);
        req.flags |= MEM_EVENT_FLAG_VCPU_PAUSED;
    }
    else if ( p2mt != p2m_ram_paging_out && p2mt != p2m_ram_paged )
    {
        /* gfn is already on its way back and vcpu is not paused */
+     p2m_unlock(p2m);
        return;
    }

    /* Send request to pager */
    req.gfn = gfn;
    req.p2mt = p2mt;
    req.vcpu_id = v->vcpu_id;

    mem_event_put_request(d, &req);
+ p2m_unlock(p2m);
}