[Qemu-devel] [PATCH 1/2] hostmem-file: Add "nopin" option for memory-backend-file

[Yang Zhong <yang.zhong@intel.com>]

Since qemu does not need pin nvdimm memory during the VFIO
hotplug, the new option can be used to avoid pin whole nvdimm
memory. The default value is still "nopin=off" as previous.

Signed-off-by: Yang Zhong <yang.zhong@intel.com>
---
 backends/hostmem-file.c | 23 +++++++++++++++++++++++
 hw/vfio/common.c        | 12 +++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index e44c319..e402077 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -33,6 +33,7 @@ struct HostMemoryBackendFile {
 
     bool share;
     bool discard_data;
+    bool nopin;
     char *mem_path;
 };
 
@@ -128,6 +129,25 @@ static void file_backend_unparent(Object *obj)
     }
 }
 
+static bool file_memory_backend_get_nopin(Object *o, Error **errp)
+{
+    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
+
+    return fb->nopin;
+}
+
+static void file_memory_backend_set_nopin(Object *o, bool value, Error **errp)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(o);
+    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
+
+    if (memory_region_size(&backend->mr)) {
+        error_setg(errp, "cannot change property value");
+        return;
+    }
+    fb->nopin = value;
+}
+
 static void
 file_backend_class_init(ObjectClass *oc, void *data)
 {
@@ -142,6 +162,9 @@ file_backend_class_init(ObjectClass *oc, void *data)
     object_class_property_add_bool(oc, "discard-data",
         file_memory_backend_get_discard_data, file_memory_backend_set_discard_data,
         &error_abort);
+    object_class_property_add_bool(oc, "nopin",
+        file_memory_backend_get_nopin, file_memory_backend_set_nopin,
+        &error_abort);
     object_class_property_add_str(oc, "mem-path",
         get_mem_path, set_mem_path,
         &error_abort);
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 7b2924c..f36ff24 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -408,7 +408,8 @@ static void vfio_listener_region_add(MemoryListener *listener,
     void *vaddr;
     int ret;
     VFIOHostDMAWindow *hostwin;
-    bool hostwin_found;
+    bool hostwin_found, nopin;
+    Object *obj = section->mr->owner;
 
     if (vfio_listener_skipped_section(section)) {
         trace_vfio_listener_region_add_skip(
@@ -424,6 +425,15 @@ static void vfio_listener_region_add(MemoryListener *listener,
         return;
     }
 
+    if (obj && object_dynamic_cast(obj, "memory-backend-file")) {
+        nopin = object_property_get_bool(obj, "nopin", NULL);
+        if (nopin) {
+            error_report("warning: If VFIO DMA still map to NVDIMM memory, "
+                         "the VM will crash");
+            return;
+        }
+    }
+
     iova = TARGET_PAGE_ALIGN(section->offset_within_address_space);
     llend = int128_make64(section->offset_within_address_space);
     llend = int128_add(llend, section->size);
-- 
1.9.1