vhost: allow backends to filter memory sections

This patch introduces a vhost op for vhost backends to allow
them to filter the memory sections that they can handle.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/virtio/vhost-user.c

@@ -1620,6 +1620,16 @@ vhost_user_crypto_close_session(struct vhost_dev *dev, uint64_t session_id)
     return 0;
 }
 
+static bool vhost_user_mem_section_filter(struct vhost_dev *dev,
+                                          MemoryRegionSection *section)
+{
+    bool result;
+
+    result = memory_region_get_fd(section->mr) >= 0;
+
+    return result;
+}
+
 const VhostOps user_ops = {
         .backend_type = VHOST_BACKEND_TYPE_USER,
         .vhost_backend_init = vhost_user_init,
@@ -1650,4 +1660,5 @@ const VhostOps user_ops = {
         .vhost_set_config = vhost_user_set_config,
         .vhost_crypto_create_session = vhost_user_crypto_create_session,
         .vhost_crypto_close_session = vhost_user_crypto_close_session,
+        .vhost_backend_mem_section_filter = vhost_user_mem_section_filter,
 };

hw/virtio/vhost.c

@@ -386,7 +386,7 @@ static int vhost_verify_ring_mappings(struct vhost_dev *dev,
     return r;
 }
 
-static bool vhost_section(MemoryRegionSection *section)
+static bool vhost_section(struct vhost_dev *dev, MemoryRegionSection *section)
 {
     bool result;
     bool log_dirty = memory_region_get_dirty_log_mask(section->mr) &
@@ -399,6 +399,11 @@ static bool vhost_section(MemoryRegionSection *section)
      */
     result &= !log_dirty;
 
+    if (result && dev->vhost_ops->vhost_backend_mem_section_filter) {
+        result &=
+            dev->vhost_ops->vhost_backend_mem_section_filter(dev, section);
+    }
+
     trace_vhost_section(section->mr->name, result);
     return result;
 }
@@ -632,7 +637,7 @@ static void vhost_region_addnop(MemoryListener *listener,
     struct vhost_dev *dev = container_of(listener, struct vhost_dev,
                                          memory_listener);
 
-    if (!vhost_section(section)) {
+    if (!vhost_section(dev, section)) {
         return;
     }
     vhost_region_add_section(dev, section);

include/hw/virtio/vhost-backend.h

@@ -101,6 +101,9 @@ typedef int (*vhost_crypto_create_session_op)(struct vhost_dev *dev,
 typedef int (*vhost_crypto_close_session_op)(struct vhost_dev *dev,
                                              uint64_t session_id);
 
+typedef bool (*vhost_backend_mem_section_filter_op)(struct vhost_dev *dev,
+                                                MemoryRegionSection *section);
+
 typedef struct VhostOps {
     VhostBackendType backend_type;
     vhost_backend_init vhost_backend_init;
@@ -138,6 +141,7 @@ typedef struct VhostOps {
     vhost_set_config_op vhost_set_config;
     vhost_crypto_create_session_op vhost_crypto_create_session;
     vhost_crypto_close_session_op vhost_crypto_close_session;
+    vhost_backend_mem_section_filter_op vhost_backend_mem_section_filter;
 } VhostOps;
 
 extern const VhostOps user_ops;