x86/mm: Consume multiple mem event responses off the ring

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Signed-off-by: Adin Scannell <adin@scanneel.ca>
Acked-by: Tim Deegan <tim@xen.org>
Committed-by: Tim Deegan <tim@xen.org>

xen/arch/x86/mm/mem_event.c

@@ -166,7 +166,7 @@ void mem_event_put_request(struct domain *d, struct mem_event_domain *med, mem_e
     notify_via_xen_event_channel(d, med->xen_port);
 }
 
-void mem_event_get_response(struct mem_event_domain *med, mem_event_response_t *rsp)
+int mem_event_get_response(struct mem_event_domain *med, mem_event_response_t *rsp)
 {
     mem_event_front_ring_t *front_ring;
     RING_IDX rsp_cons;
@@ -176,6 +176,12 @@ void mem_event_get_response(struct mem_event_domain *med, mem_event_response_t *
     front_ring = &med->front_ring;
     rsp_cons = front_ring->rsp_cons;
 
+    if ( !RING_HAS_UNCONSUMED_RESPONSES(front_ring) )
+    {
+        mem_event_ring_unlock(med);
+        return 0;
+    }
+
     /* Copy response */
     memcpy(rsp, RING_GET_RESPONSE(front_ring, rsp_cons), sizeof(*rsp));
     rsp_cons++;
@@ -185,6 +191,8 @@ void mem_event_get_response(struct mem_event_domain *med, mem_event_response_t *
     front_ring->sring->rsp_event = rsp_cons + 1;
 
     mem_event_ring_unlock(med);
+
+    return 1;
 }
 
 void mem_event_unpause_vcpus(struct domain *d)

xen/arch/x86/mm/mem_sharing.c

@@ -300,12 +300,13 @@ int mem_sharing_sharing_resume(struct domain *d)
 {
     mem_event_response_t rsp;
 
-    /* Get request off the ring */
-    mem_event_get_response(&d->mem_event->share, &rsp);
-
-    /* Unpause domain/vcpu */
-    if( rsp.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
-        vcpu_unpause(d->vcpu[rsp.vcpu_id]);
+    /* Get all requests off the ring */
+    while ( mem_event_get_response(&d->mem_event->share, &rsp) )
+    {
+        /* Unpause domain/vcpu */
+        if ( rsp.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
+            vcpu_unpause(d->vcpu[rsp.vcpu_id]);
+    }
 
     return 0;
 }

xen/arch/x86/mm/p2m.c

@@ -1053,31 +1053,31 @@ void p2m_mem_paging_resume(struct domain *d)
     p2m_access_t a;
     mfn_t mfn;
 
-    /* Pull the response off the ring */
-    mem_event_get_response(&d->mem_event->paging, &rsp);
-
-    /* Fix p2m entry if the page was not dropped */
-    if ( !(rsp.flags & MEM_EVENT_FLAG_DROP_PAGE) )
+    /* Pull all responses off the ring */
+    while( mem_event_get_response(&d->mem_event->paging, &rsp) )
     {
-        p2m_lock(p2m);
-        mfn = p2m->get_entry(p2m, rsp.gfn, &p2mt, &a, p2m_query, NULL);
-        /* Allow only pages which were prepared properly, or pages which
-         * were nominated but not evicted */
-        if ( mfn_valid(mfn) && 
-             (p2mt == p2m_ram_paging_in || p2mt == p2m_ram_paging_in_start) )
+        /* Fix p2m entry if the page was not dropped */
+        if ( !(rsp.flags & MEM_EVENT_FLAG_DROP_PAGE) )
         {
-            set_p2m_entry(p2m, rsp.gfn, mfn, PAGE_ORDER_4K, 
-                            paging_mode_log_dirty(d) ? p2m_ram_logdirty : p2m_ram_rw, 
-                            a);
-            set_gpfn_from_mfn(mfn_x(mfn), rsp.gfn);
+            p2m_lock(p2m);
+            mfn = p2m->get_entry(p2m, rsp.gfn, &p2mt, &a, p2m_query, NULL);
+            /* Allow only pages which were prepared properly, or pages which
+             * were nominated but not evicted */
+            if ( mfn_valid(mfn) && 
+                 (p2mt == p2m_ram_paging_in || p2mt == p2m_ram_paging_in_start) )
+            {
+                set_p2m_entry(p2m, rsp.gfn, mfn, PAGE_ORDER_4K, 
+                                paging_mode_log_dirty(d) ? p2m_ram_logdirty : 
+                                p2m_ram_rw, a);
+                set_gpfn_from_mfn(mfn_x(mfn), rsp.gfn);
+            }
+            p2m_unlock(p2m);
         }
-        p2m_unlock(p2m);
+        /* Unpause domain */
+        if ( rsp.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
+            vcpu_unpause(d->vcpu[rsp.vcpu_id]);
     }
 
-    /* Unpause domain */
-    if ( rsp.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
-        vcpu_unpause(d->vcpu[rsp.vcpu_id]);
-
     /* Unpause any domains that were paused because the ring was full */
     mem_event_unpause_vcpus(d);
 }
@@ -1161,11 +1161,13 @@ void p2m_mem_access_resume(struct domain *d)
 {
     mem_event_response_t rsp;
 
-    mem_event_get_response(&d->mem_event->access, &rsp);
-
-    /* Unpause domain */
-    if ( rsp.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
-        vcpu_unpause(d->vcpu[rsp.vcpu_id]);
+    /* Pull all responses off the ring */
+    while( mem_event_get_response(&d->mem_event->access, &rsp) )
+    {
+        /* Unpause domain */
+        if ( rsp.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
+            vcpu_unpause(d->vcpu[rsp.vcpu_id]);
+    }
 
     /* Unpause any domains that were paused because the ring was full or no listener 
      * was available */

xen/include/asm-x86/mem_event.h

@@ -29,7 +29,7 @@ void mem_event_mark_and_pause(struct vcpu *v);
 int mem_event_check_ring(struct domain *d, struct mem_event_domain *med);
 void mem_event_put_req_producers(struct mem_event_domain *med);
 void mem_event_put_request(struct domain *d, struct mem_event_domain *med, mem_event_request_t *req);
-void mem_event_get_response(struct mem_event_domain *med, mem_event_response_t *rsp);
+int mem_event_get_response(struct mem_event_domain *med, mem_event_response_t *rsp);
 void mem_event_unpause_vcpus(struct domain *d);
 
 int mem_event_domctl(struct domain *d, xen_domctl_mem_event_op_t *mec,