hostmem: introduce "prealloc-threads" property

the property will allow user to specify number of threads to use
in pre-allocation stage. It also will allow to reduce implicit
hostmem dependency on current_machine.
On object creation it will default to 1, but via machine
compat property it will be updated to MachineState::smp::cpus
to keep current behavior for hostmem and main RAM (which is
now also hostmem based).

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20200219160953.13771-77-imammedo@redhat.com>

1 files changed, 39 insertions, 4 deletions

diff --git a/backends/hostmem.c b/backends/hostmem.c
index e773bdfa6e..0988986016 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -223,7 +223,6 @@ static void host_memory_backend_set_prealloc(Object *obj, bool value,
 {
     Error *local_err = NULL;
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
-    MachineState *ms = MACHINE(qdev_get_machine());
 
     if (backend->force_prealloc) {
         if (value) {
@@ -243,7 +242,7 @@ static void host_memory_backend_set_prealloc(Object *obj, bool value,
         void *ptr = memory_region_get_ram_ptr(&backend->mr);
         uint64_t sz = memory_region_size(&backend->mr);
 
-        os_mem_prealloc(fd, ptr, sz, ms->smp.cpus, &local_err);
+        os_mem_prealloc(fd, ptr, sz, backend->prealloc_threads, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
             return;
@@ -252,14 +251,45 @@ static void host_memory_backend_set_prealloc(Object *obj, bool value,
     }
 }
 
+static void host_memory_backend_get_prealloc_threads(Object *obj, Visitor *v,
+    const char *name, void *opaque, Error **errp)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+    visit_type_uint32(v, name, &backend->prealloc_threads, errp);
+}
+
+static void host_memory_backend_set_prealloc_threads(Object *obj, Visitor *v,
+    const char *name, void *opaque, Error **errp)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+    Error *local_err = NULL;
+    uint32_t value;
+
+    visit_type_uint32(v, name, &value, &local_err);
+    if (local_err) {
+        goto out;
+    }
+    if (value <= 0) {
+        error_setg(&local_err,
+                   "property '%s' of %s doesn't take value '%d'",
+                   name, object_get_typename(obj), value);
+        goto out;
+    }
+    backend->prealloc_threads = value;
+out:
+    error_propagate(errp, local_err);
+}
+
 static void host_memory_backend_init(Object *obj)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
     MachineState *machine = MACHINE(qdev_get_machine());
 
+    /* TODO: convert access to globals to compat properties */
     backend->merge = machine_mem_merge(machine);
     backend->dump = machine_dump_guest_core(machine);
     backend->prealloc = mem_prealloc;
+    backend->prealloc_threads = 1;
 }
 
 static void host_memory_backend_post_init(Object *obj)
@@ -313,7 +343,6 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(uc);
     HostMemoryBackendClass *bc = MEMORY_BACKEND_GET_CLASS(uc);
-    MachineState *ms = MACHINE(qdev_get_machine());
     Error *local_err = NULL;
     void *ptr;
     uint64_t sz;
@@ -378,7 +407,7 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
          */
         if (backend->prealloc) {
             os_mem_prealloc(memory_region_get_fd(&backend->mr), ptr, sz,
-                            ms->smp.cpus, &local_err);
+                            backend->prealloc_threads, &local_err);
             if (local_err) {
                 goto out;
             }
@@ -456,6 +485,12 @@ host_memory_backend_class_init(ObjectClass *oc, void *data)
         host_memory_backend_set_prealloc, &error_abort);
     object_class_property_set_description(oc, "prealloc",
         "Preallocate memory", &error_abort);
+    object_class_property_add(oc, "prealloc-threads", "int",
+        host_memory_backend_get_prealloc_threads,
+        host_memory_backend_set_prealloc_threads,
+        NULL, NULL, &error_abort);
+    object_class_property_set_description(oc, "prealloc-threads",
+        "Number of CPU threads to use for prealloc", &error_abort);
     object_class_property_add(oc, "size", "int",
         host_memory_backend_get_size,
         host_memory_backend_set_size,