@@ -8,3 +8,5 @@ common-obj-$(CONFIG_LINUX) += hostmem-file.o
common-obj-y += cryptodev.o
common-obj-y += cryptodev-builtin.o
+
+common-obj-$(CONFIG_LINUX) += hostmem-memfd.o
new file mode 100644
@@ -0,0 +1,170 @@
+/*
+ * QEMU host memfd memory backend
+ *
+ * Copyright (C) 2018 Red Hat Inc
+ *
+ * Authors:
+ * Marc-André Lureau <marcandre.lureau@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "sysemu/hostmem.h"
+#include "sysemu/sysemu.h"
+#include "qom/object_interfaces.h"
+#include "qemu/memfd.h"
+#include "qapi/error.h"
+
+#define TYPE_MEMORY_BACKEND_MEMFD "memory-backend-memfd"
+
+#define MEMORY_BACKEND_MEMFD(obj) \
+ OBJECT_CHECK(HostMemoryBackendMemfd, (obj), TYPE_MEMORY_BACKEND_MEMFD)
+
+typedef struct HostMemoryBackendMemfd HostMemoryBackendMemfd;
+
+struct HostMemoryBackendMemfd {
+ HostMemoryBackend parent_obj;
+
+ bool hugetlb;
+ uint64_t hugetlbsize;
+ bool seal;
+};
+
+static void
+memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
+{
+ HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(backend);
+ char *name;
+ int fd;
+
+ if (!backend->size) {
+ error_setg(errp, "can't create backend with size 0");
+ return;
+ }
+
+ if (host_memory_backend_mr_inited(backend)) {
+ return;
+ }
+
+ backend->force_prealloc = mem_prealloc;
+ fd = qemu_memfd_create(TYPE_MEMORY_BACKEND_MEMFD, backend->size,
+ m->hugetlb, m->hugetlbsize, m->seal ?
+ F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL : 0,
+ errp);
+ if (fd == -1) {
+ return;
+ }
+
+ name = object_get_canonical_path(OBJECT(backend));
+ memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend),
+ name, backend->size, true, fd, errp);
+ g_free(name);
+}
+
+static bool
+memfd_backend_get_hugetlb(Object *o, Error **errp)
+{
+ return MEMORY_BACKEND_MEMFD(o)->hugetlb;
+}
+
+static void
+memfd_backend_set_hugetlb(Object *o, bool value, Error **errp)
+{
+ MEMORY_BACKEND_MEMFD(o)->hugetlb = value;
+}
+
+static void
+memfd_backend_set_hugetlbsize(Object *obj, Visitor *v, const char *name,
+ void *opaque, Error **errp)
+{
+ HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(obj);
+ Error *local_err = NULL;
+ uint64_t value;
+
+ if (host_memory_backend_mr_inited(MEMORY_BACKEND(obj))) {
+ error_setg(&local_err, "cannot change property value");
+ goto out;
+ }
+
+ visit_type_size(v, name, &value, &local_err);
+ if (local_err) {
+ goto out;
+ }
+ if (!value) {
+ error_setg(&local_err, "Property '%s.%s' doesn't take value '%"
+ PRIu64 "'", object_get_typename(obj), name, value);
+ goto out;
+ }
+ m->hugetlbsize = value;
+out:
+ error_propagate(errp, local_err);
+}
+
+static void
+memfd_backend_get_hugetlbsize(Object *obj, Visitor *v, const char *name,
+ void *opaque, Error **errp)
+{
+ HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(obj);
+ uint64_t value = m->hugetlbsize;
+
+ visit_type_size(v, name, &value, errp);
+}
+
+static bool
+memfd_backend_get_seal(Object *o, Error **errp)
+{
+ return MEMORY_BACKEND_MEMFD(o)->seal;
+}
+
+static void
+memfd_backend_set_seal(Object *o, bool value, Error **errp)
+{
+ MEMORY_BACKEND_MEMFD(o)->seal = value;
+}
+
+static void
+memfd_backend_instance_init(Object *obj)
+{
+ HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(obj);
+
+ /* default to sealed file */
+ m->seal = true;
+}
+
+static void
+memfd_backend_class_init(ObjectClass *oc, void *data)
+{
+ HostMemoryBackendClass *bc = MEMORY_BACKEND_CLASS(oc);
+
+ bc->alloc = memfd_backend_memory_alloc;
+
+ object_class_property_add_bool(oc, "hugetlb",
+ memfd_backend_get_hugetlb,
+ memfd_backend_set_hugetlb,
+ &error_abort);
+ object_class_property_add(oc, "hugetlbsize", "int",
+ memfd_backend_get_hugetlbsize,
+ memfd_backend_set_hugetlbsize,
+ NULL, NULL, &error_abort);
+ object_class_property_add_bool(oc, "seal",
+ memfd_backend_get_seal,
+ memfd_backend_set_seal,
+ &error_abort);
+}
+
+static const TypeInfo memfd_backend_info = {
+ .name = TYPE_MEMORY_BACKEND_MEMFD,
+ .parent = TYPE_MEMORY_BACKEND,
+ .instance_init = memfd_backend_instance_init,
+ .class_init = memfd_backend_class_init,
+ .instance_size = sizeof(HostMemoryBackendMemfd),
+};
+
+static void register_types(void)
+{
+ type_register_static(&memfd_backend_info);
+}
+
+type_init(register_types);
@@ -4024,6 +4024,28 @@ Memory backend objects offer more control than the @option{-m} option that is
traditionally used to define guest RAM. Please refer to
@option{memory-backend-file} for a description of the options.
+@item -object memory-backend-memfd,id=@var{id},merge=@var{on|off},dump=@var{on|off},prealloc=@var{on|off},size=@var{size},host-nodes=@var{host-nodes},policy=@var{default|preferred|bind|interleave},seal=@var{on|off},hugetlb=@var{on|off},hugetlbsize=@var{size}
+
+Creates an anonymous memory file backend object, which allows QEMU to
+share the memory with an external process (e.g. when using
+vhost-user). The memory is allocated with memfd and optional
+sealing. (Linux only)
+
+The @option{seal} option creates a sealed-file, that will block
+further resizing the memory ('on' by default).
+
+The @option{hugetlb} option specify the file to be created resides in
+the hugetlbfs filesystem (since Linux 4.14). Used in conjunction with
+the @option{hugetlb} option, the @option{hugetlbsize} option specify
+the hugetlb page size on systems that support multiple hugetlb page
+sizes (it must be a power of 2 value supported by the system).
+
+In some versions of Linux, the @option{hugetlb} option is incompatible
+with the @option{seal} option (requires at least Linux 4.16).
+
+Please refer to @option{memory-backend-file} for a description of the
+other options.
+
@item -object rng-random,id=@var{id},filename=@var{/dev/random}
Creates a random number generator backend which obtains entropy from