backends/hostmem.c - qemu - Git at Google

 /*
  * QEMU Host Memory Backend
  *
  * Copyright (C) 2013-2014 Red Hat Inc
  *
  * Authors:
  *   Igor Mammedov <imammedo@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 "sysemu/hostmem.h"
 #include "hw/boards.h"
 #include "qapi/error.h"
 #include "qapi/qapi-builtin-visit.h"
 #include "qapi/visitor.h"
 #include "qemu/config-file.h"
 #include "qom/object_interfaces.h"
 #include "qemu/mmap-alloc.h"

 #ifdef CONFIG_NUMA
 #include <numaif.h>
 QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_DEFAULT != MPOL_DEFAULT);
 QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_PREFERRED != MPOL_PREFERRED);
 QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_BIND != MPOL_BIND);
 QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_INTERLEAVE != MPOL_INTERLEAVE);
 #endif

 static void
 host_memory_backend_get_size(Object *obj, Visitor *v, const char *name,
                              void *opaque, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
     uint64_t value = backend->size;

     visit_type_size(v, name, &value, errp);
 }

 static void
 host_memory_backend_set_size(Object *obj, Visitor *v, const char *name,
                              void *opaque, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
     Error *local_err = NULL;
     uint64_t value;

     if (host_memory_backend_mr_inited(backend)) {
         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;
     }
     backend->size = value;
 out:
     error_propagate(errp, local_err);
 }

 static void
 host_memory_backend_get_host_nodes(Object *obj, Visitor *v, const char *name,
                                    void *opaque, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
     uint16List *host_nodes = NULL;
     uint16List **node = &host_nodes;
     unsigned long value;

     value = find_first_bit(backend->host_nodes, MAX_NODES);
     if (value == MAX_NODES) {
         return;
     }

     *node = g_malloc0(sizeof(**node));
     (*node)->value = value;
     node = &(*node)->next;

     do {
         value = find_next_bit(backend->host_nodes, MAX_NODES, value + 1);
         if (value == MAX_NODES) {
             break;
         }

         *node = g_malloc0(sizeof(**node));
         (*node)->value = value;
         node = &(*node)->next;
     } while (true);

     visit_type_uint16List(v, name, &host_nodes, errp);
 }

 static void
 host_memory_backend_set_host_nodes(Object *obj, Visitor *v, const char *name,
                                    void *opaque, Error **errp)
 {
 #ifdef CONFIG_NUMA
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
     uint16List *l, *host_nodes = NULL;

     visit_type_uint16List(v, name, &host_nodes, errp);

     for (l = host_nodes; l; l = l->next) {
         if (l->value >= MAX_NODES) {
             error_setg(errp, "Invalid host-nodes value: %d", l->value);
             goto out;
         }
     }

     for (l = host_nodes; l; l = l->next) {
         bitmap_set(backend->host_nodes, l->value, 1);
     }

 out:
     qapi_free_uint16List(host_nodes);
 #else
     error_setg(errp, "NUMA node binding are not supported by this QEMU");
 #endif
 }

 static int
 host_memory_backend_get_policy(Object *obj, Error **errp G_GNUC_UNUSED)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
     return backend->policy;
 }

 static void
 host_memory_backend_set_policy(Object *obj, int policy, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
     backend->policy = policy;

 #ifndef CONFIG_NUMA
     if (policy != HOST_MEM_POLICY_DEFAULT) {
         error_setg(errp, "NUMA policies are not supported by this QEMU");
     }
 #endif
 }

 static bool host_memory_backend_get_merge(Object *obj, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);

     return backend->merge;
 }

 static void host_memory_backend_set_merge(Object *obj, bool value, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);

     if (!host_memory_backend_mr_inited(backend)) {
         backend->merge = value;
         return;
     }

     if (value != backend->merge) {
         void *ptr = memory_region_get_ram_ptr(&backend->mr);
         uint64_t sz = memory_region_size(&backend->mr);

         qemu_madvise(ptr, sz,
                      value ? QEMU_MADV_MERGEABLE : QEMU_MADV_UNMERGEABLE);
         backend->merge = value;
     }
 }

 static bool host_memory_backend_get_dump(Object *obj, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);

     return backend->dump;
 }

 static void host_memory_backend_set_dump(Object *obj, bool value, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);

     if (!host_memory_backend_mr_inited(backend)) {
         backend->dump = value;
         return;
     }

     if (value != backend->dump) {
         void *ptr = memory_region_get_ram_ptr(&backend->mr);
         uint64_t sz = memory_region_size(&backend->mr);

         qemu_madvise(ptr, sz,
                      value ? QEMU_MADV_DODUMP : QEMU_MADV_DONTDUMP);
         backend->dump = value;
     }
 }

 static bool host_memory_backend_get_prealloc(Object *obj, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);

     return backend->prealloc || backend->force_prealloc;
 }

 static void host_memory_backend_set_prealloc(Object *obj, bool value,
                                              Error **errp)
 {
     Error *local_err = NULL;
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);

     if (backend->force_prealloc) {
         if (value) {
             error_setg(errp,
                        "remove -mem-prealloc to use the prealloc property");
             return;
         }
     }

     if (!host_memory_backend_mr_inited(backend)) {
         backend->prealloc = value;
         return;
     }

     if (value && !backend->prealloc) {
         int fd = memory_region_get_fd(&backend->mr);
         void *ptr = memory_region_get_ram_ptr(&backend->mr);
         uint64_t sz = memory_region_size(&backend->mr);

         os_mem_prealloc(fd, ptr, sz, smp_cpus, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
             return;
         }
         backend->prealloc = true;
     }
 }

 static void host_memory_backend_init(Object *obj)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
     MachineState *machine = MACHINE(qdev_get_machine());

     backend->merge = machine_mem_merge(machine);
     backend->dump = machine_dump_guest_core(machine);
     backend->prealloc = mem_prealloc;
 }

 bool host_memory_backend_mr_inited(HostMemoryBackend *backend)
 {
     /*
      * NOTE: We forbid zero-length memory backend, so here zero means
      * "we haven't inited the backend memory region yet".
      */
     return memory_region_size(&backend->mr) != 0;
 }

 MemoryRegion *host_memory_backend_get_memory(HostMemoryBackend *backend)
 {
     return host_memory_backend_mr_inited(backend) ? &backend->mr : NULL;
 }

 void host_memory_backend_set_mapped(HostMemoryBackend *backend, bool mapped)
 {
     backend->is_mapped = mapped;
 }

 bool host_memory_backend_is_mapped(HostMemoryBackend *backend)
 {
     return backend->is_mapped;
 }

 #ifdef __linux__
 size_t host_memory_backend_pagesize(HostMemoryBackend *memdev)
 {
     Object *obj = OBJECT(memdev);
     char *path = object_property_get_str(obj, "mem-path", NULL);
     size_t pagesize = qemu_mempath_getpagesize(path);

     g_free(path);
     return pagesize;
 }
 #else
 size_t host_memory_backend_pagesize(HostMemoryBackend *memdev)
 {
     return getpagesize();
 }
 #endif

 static void
 host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(uc);
     HostMemoryBackendClass *bc = MEMORY_BACKEND_GET_CLASS(uc);
     Error *local_err = NULL;
     void *ptr;
     uint64_t sz;

     if (bc->alloc) {
         bc->alloc(backend, &local_err);
         if (local_err) {
             goto out;
         }

         ptr = memory_region_get_ram_ptr(&backend->mr);
         sz = memory_region_size(&backend->mr);

         if (backend->merge) {
             qemu_madvise(ptr, sz, QEMU_MADV_MERGEABLE);
         }
         if (!backend->dump) {
             qemu_madvise(ptr, sz, QEMU_MADV_DONTDUMP);
         }
 #ifdef CONFIG_NUMA
         unsigned long lastbit = find_last_bit(backend->host_nodes, MAX_NODES);
         /* lastbit == MAX_NODES means maxnode = 0 */
         unsigned long maxnode = (lastbit + 1) % (MAX_NODES + 1);
         /* ensure policy won't be ignored in case memory is preallocated
          * before mbind(). note: MPOL_MF_STRICT is ignored on hugepages so
          * this doesn't catch hugepage case. */
         unsigned flags = MPOL_MF_STRICT | MPOL_MF_MOVE;

         /* check for invalid host-nodes and policies and give more verbose
          * error messages than mbind(). */
         if (maxnode && backend->policy == MPOL_DEFAULT) {
             error_setg(errp, "host-nodes must be empty for policy default,"
                        " or you should explicitly specify a policy other"
                        " than default");
             return;
         } else if (maxnode == 0 && backend->policy != MPOL_DEFAULT) {
             error_setg(errp, "host-nodes must be set for policy %s",
                        HostMemPolicy_str(backend->policy));
             return;
         }

         /* We can have up to MAX_NODES nodes, but we need to pass maxnode+1
          * as argument to mbind() due to an old Linux bug (feature?) which
          * cuts off the last specified node. This means backend->host_nodes
          * must have MAX_NODES+1 bits available.
          */
         assert(sizeof(backend->host_nodes) >=
                BITS_TO_LONGS(MAX_NODES + 1) * sizeof(unsigned long));
         assert(maxnode <= MAX_NODES);
         if (mbind(ptr, sz, backend->policy,
                   maxnode ? backend->host_nodes : NULL, maxnode + 1, flags)) {
             if (backend->policy != MPOL_DEFAULT || errno != ENOSYS) {
                 error_setg_errno(errp, errno,
                                  "cannot bind memory to host NUMA nodes");
                 return;
             }
         }
 #endif
         /* Preallocate memory after the NUMA policy has been instantiated.
          * This is necessary to guarantee memory is allocated with
          * specified NUMA policy in place.
          */
         if (backend->prealloc) {
             os_mem_prealloc(memory_region_get_fd(&backend->mr), ptr, sz,
                             smp_cpus, &local_err);
             if (local_err) {
                 goto out;
             }
         }
     }
 out:
     error_propagate(errp, local_err);
 }

 static bool
 host_memory_backend_can_be_deleted(UserCreatable *uc)
 {
     if (host_memory_backend_is_mapped(MEMORY_BACKEND(uc))) {
         return false;
     } else {
         return true;
     }
 }

 static bool host_memory_backend_get_share(Object *o, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(o);

     return backend->share;
 }

 static void host_memory_backend_set_share(Object *o, bool value, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(o);

     if (host_memory_backend_mr_inited(backend)) {
         error_setg(errp, "cannot change property value");
         return;
     }
     backend->share = value;
 }

 static void
 host_memory_backend_class_init(ObjectClass *oc, void *data)
 {
     UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);

     ucc->complete = host_memory_backend_memory_complete;
     ucc->can_be_deleted = host_memory_backend_can_be_deleted;

     object_class_property_add_bool(oc, "merge",
         host_memory_backend_get_merge,
         host_memory_backend_set_merge, &error_abort);
     object_class_property_set_description(oc, "merge",
         "Mark memory as mergeable", &error_abort);
     object_class_property_add_bool(oc, "dump",
         host_memory_backend_get_dump,
         host_memory_backend_set_dump, &error_abort);
     object_class_property_set_description(oc, "dump",
         "Set to 'off' to exclude from core dump", &error_abort);
     object_class_property_add_bool(oc, "prealloc",
         host_memory_backend_get_prealloc,
         host_memory_backend_set_prealloc, &error_abort);
     object_class_property_set_description(oc, "prealloc",
         "Preallocate memory", &error_abort);
     object_class_property_add(oc, "size", "int",
         host_memory_backend_get_size,
         host_memory_backend_set_size,
         NULL, NULL, &error_abort);
     object_class_property_set_description(oc, "size",
         "Size of the memory region (ex: 500M)", &error_abort);
     object_class_property_add(oc, "host-nodes", "int",
         host_memory_backend_get_host_nodes,
         host_memory_backend_set_host_nodes,
         NULL, NULL, &error_abort);
     object_class_property_set_description(oc, "host-nodes",
         "Binds memory to the list of NUMA host nodes", &error_abort);
     object_class_property_add_enum(oc, "policy", "HostMemPolicy",
         &HostMemPolicy_lookup,
         host_memory_backend_get_policy,
         host_memory_backend_set_policy, &error_abort);
     object_class_property_set_description(oc, "policy",
         "Set the NUMA policy", &error_abort);
     object_class_property_add_bool(oc, "share",
         host_memory_backend_get_share, host_memory_backend_set_share,
         &error_abort);
     object_class_property_set_description(oc, "share",
         "Mark the memory as private to QEMU or shared", &error_abort);
 }

 static const TypeInfo host_memory_backend_info = {
     .name = TYPE_MEMORY_BACKEND,
     .parent = TYPE_OBJECT,
     .abstract = true,
     .class_size = sizeof(HostMemoryBackendClass),
     .class_init = host_memory_backend_class_init,
     .instance_size = sizeof(HostMemoryBackend),
     .instance_init = host_memory_backend_init,
     .interfaces = (InterfaceInfo[]) {
         { TYPE_USER_CREATABLE },
         { }
     }
 };

 static void register_types(void)
 {
     type_register_static(&host_memory_backend_info);
 }

 type_init(register_types);
	/*
	* QEMU Host Memory Backend
	*
	* Copyright (C) 2013-2014 Red Hat Inc
	*
	* Authors:
	* Igor Mammedov <imammedo@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 "sysemu/hostmem.h"
	#include "hw/boards.h"
	#include "qapi/error.h"
	#include "qapi/qapi-builtin-visit.h"
	#include "qapi/visitor.h"
	#include "qemu/config-file.h"
	#include "qom/object_interfaces.h"
	#include "qemu/mmap-alloc.h"

	#ifdef CONFIG_NUMA
	#include <numaif.h>
	QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_DEFAULT != MPOL_DEFAULT);
	QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_PREFERRED != MPOL_PREFERRED);
	QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_BIND != MPOL_BIND);
	QEMU_BUILD_BUG_ON(HOST_MEM_POLICY_INTERLEAVE != MPOL_INTERLEAVE);
	#endif

	static void
	host_memory_backend_get_size(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);
	uint64_t value = backend->size;

	visit_type_size(v, name, &value, errp);
	}

	static void
	host_memory_backend_set_size(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);
	Error *local_err = NULL;
	uint64_t value;

	if (host_memory_backend_mr_inited(backend)) {
	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;
	}
	backend->size = value;
	out:
	error_propagate(errp, local_err);
	}

	static void
	host_memory_backend_get_host_nodes(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);
	uint16List *host_nodes = NULL;
	uint16List **node = &host_nodes;
	unsigned long value;

	value = find_first_bit(backend->host_nodes, MAX_NODES);
	if (value == MAX_NODES) {
	return;
	}

	node = g_malloc0(sizeof(*node));
	(*node)->value = value;
	node = &(*node)->next;

	do {
	value = find_next_bit(backend->host_nodes, MAX_NODES, value + 1);
	if (value == MAX_NODES) {
	break;
	}

	node = g_malloc0(sizeof(*node));
	(*node)->value = value;
	node = &(*node)->next;
	} while (true);

	visit_type_uint16List(v, name, &host_nodes, errp);
	}

	static void
	host_memory_backend_set_host_nodes(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	#ifdef CONFIG_NUMA
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);
	uint16List l, host_nodes = NULL;

	visit_type_uint16List(v, name, &host_nodes, errp);

	for (l = host_nodes; l; l = l->next) {
	if (l->value >= MAX_NODES) {
	error_setg(errp, "Invalid host-nodes value: %d", l->value);
	goto out;
	}
	}

	for (l = host_nodes; l; l = l->next) {
	bitmap_set(backend->host_nodes, l->value, 1);
	}

	out:
	qapi_free_uint16List(host_nodes);
	#else
	error_setg(errp, "NUMA node binding are not supported by this QEMU");
	#endif
	}

	static int
	host_memory_backend_get_policy(Object obj, Error *errp G_GNUC_UNUSED)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);
	return backend->policy;
	}

	static void
	host_memory_backend_set_policy(Object obj, int policy, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);
	backend->policy = policy;

	#ifndef CONFIG_NUMA
	if (policy != HOST_MEM_POLICY_DEFAULT) {
	error_setg(errp, "NUMA policies are not supported by this QEMU");
	}
	#endif
	}

	static bool host_memory_backend_get_merge(Object obj, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);

	return backend->merge;
	}

	static void host_memory_backend_set_merge(Object obj, bool value, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);

	if (!host_memory_backend_mr_inited(backend)) {
	backend->merge = value;
	return;
	}

	if (value != backend->merge) {
	void *ptr = memory_region_get_ram_ptr(&backend->mr);
	uint64_t sz = memory_region_size(&backend->mr);

	qemu_madvise(ptr, sz,
	value ? QEMU_MADV_MERGEABLE : QEMU_MADV_UNMERGEABLE);
	backend->merge = value;
	}
	}

	static bool host_memory_backend_get_dump(Object obj, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);

	return backend->dump;
	}

	static void host_memory_backend_set_dump(Object obj, bool value, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);

	if (!host_memory_backend_mr_inited(backend)) {
	backend->dump = value;
	return;
	}

	if (value != backend->dump) {
	void *ptr = memory_region_get_ram_ptr(&backend->mr);
	uint64_t sz = memory_region_size(&backend->mr);

	qemu_madvise(ptr, sz,
	value ? QEMU_MADV_DODUMP : QEMU_MADV_DONTDUMP);
	backend->dump = value;
	}
	}

	static bool host_memory_backend_get_prealloc(Object obj, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);

	return backend->prealloc \|\| backend->force_prealloc;
	}

	static void host_memory_backend_set_prealloc(Object *obj, bool value,
	Error **errp)
	{
	Error *local_err = NULL;
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);

	if (backend->force_prealloc) {
	if (value) {
	error_setg(errp,
	"remove -mem-prealloc to use the prealloc property");
	return;
	}
	}

	if (!host_memory_backend_mr_inited(backend)) {
	backend->prealloc = value;
	return;
	}

	if (value && !backend->prealloc) {
	int fd = memory_region_get_fd(&backend->mr);
	void *ptr = memory_region_get_ram_ptr(&backend->mr);
	uint64_t sz = memory_region_size(&backend->mr);

	os_mem_prealloc(fd, ptr, sz, smp_cpus, &local_err);
	if (local_err) {
	error_propagate(errp, local_err);
	return;
	}
	backend->prealloc = true;
	}
	}

	static void host_memory_backend_init(Object *obj)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(obj);
	MachineState *machine = MACHINE(qdev_get_machine());

	backend->merge = machine_mem_merge(machine);
	backend->dump = machine_dump_guest_core(machine);
	backend->prealloc = mem_prealloc;
	}

	bool host_memory_backend_mr_inited(HostMemoryBackend *backend)
	{
	/*
	* NOTE: We forbid zero-length memory backend, so here zero means
	* "we haven't inited the backend memory region yet".
	*/
	return memory_region_size(&backend->mr) != 0;
	}

	MemoryRegion host_memory_backend_get_memory(HostMemoryBackend backend)
	{
	return host_memory_backend_mr_inited(backend) ? &backend->mr : NULL;
	}

	void host_memory_backend_set_mapped(HostMemoryBackend *backend, bool mapped)
	{
	backend->is_mapped = mapped;
	}

	bool host_memory_backend_is_mapped(HostMemoryBackend *backend)
	{
	return backend->is_mapped;
	}

	#ifdef __linux__
	size_t host_memory_backend_pagesize(HostMemoryBackend *memdev)
	{
	Object *obj = OBJECT(memdev);
	char *path = object_property_get_str(obj, "mem-path", NULL);
	size_t pagesize = qemu_mempath_getpagesize(path);

	g_free(path);
	return pagesize;
	}
	#else
	size_t host_memory_backend_pagesize(HostMemoryBackend *memdev)
	{
	return getpagesize();
	}
	#endif

	static void
	host_memory_backend_memory_complete(UserCreatable uc, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(uc);
	HostMemoryBackendClass *bc = MEMORY_BACKEND_GET_CLASS(uc);
	Error *local_err = NULL;
	void *ptr;
	uint64_t sz;

	if (bc->alloc) {
	bc->alloc(backend, &local_err);
	if (local_err) {
	goto out;
	}

	ptr = memory_region_get_ram_ptr(&backend->mr);
	sz = memory_region_size(&backend->mr);

	if (backend->merge) {
	qemu_madvise(ptr, sz, QEMU_MADV_MERGEABLE);
	}
	if (!backend->dump) {
	qemu_madvise(ptr, sz, QEMU_MADV_DONTDUMP);
	}
	#ifdef CONFIG_NUMA
	unsigned long lastbit = find_last_bit(backend->host_nodes, MAX_NODES);
	/* lastbit == MAX_NODES means maxnode = 0 */
	unsigned long maxnode = (lastbit + 1) % (MAX_NODES + 1);
	/* ensure policy won't be ignored in case memory is preallocated
	* before mbind(). note: MPOL_MF_STRICT is ignored on hugepages so
	* this doesn't catch hugepage case. */
	unsigned flags = MPOL_MF_STRICT \| MPOL_MF_MOVE;

	/* check for invalid host-nodes and policies and give more verbose
	* error messages than mbind(). */
	if (maxnode && backend->policy == MPOL_DEFAULT) {
	error_setg(errp, "host-nodes must be empty for policy default,"
	" or you should explicitly specify a policy other"
	" than default");
	return;
	} else if (maxnode == 0 && backend->policy != MPOL_DEFAULT) {
	error_setg(errp, "host-nodes must be set for policy %s",
	HostMemPolicy_str(backend->policy));
	return;
	}

	/* We can have up to MAX_NODES nodes, but we need to pass maxnode+1
	* as argument to mbind() due to an old Linux bug (feature?) which
	* cuts off the last specified node. This means backend->host_nodes
	* must have MAX_NODES+1 bits available.
	*/
	assert(sizeof(backend->host_nodes) >=
	BITS_TO_LONGS(MAX_NODES + 1) * sizeof(unsigned long));
	assert(maxnode <= MAX_NODES);
	if (mbind(ptr, sz, backend->policy,
	maxnode ? backend->host_nodes : NULL, maxnode + 1, flags)) {
	if (backend->policy != MPOL_DEFAULT \|\| errno != ENOSYS) {
	error_setg_errno(errp, errno,
	"cannot bind memory to host NUMA nodes");
	return;
	}
	}
	#endif
	/* Preallocate memory after the NUMA policy has been instantiated.
	* This is necessary to guarantee memory is allocated with
	* specified NUMA policy in place.
	*/
	if (backend->prealloc) {
	os_mem_prealloc(memory_region_get_fd(&backend->mr), ptr, sz,
	smp_cpus, &local_err);
	if (local_err) {
	goto out;
	}
	}
	}
	out:
	error_propagate(errp, local_err);
	}

	static bool
	host_memory_backend_can_be_deleted(UserCreatable *uc)
	{
	if (host_memory_backend_is_mapped(MEMORY_BACKEND(uc))) {
	return false;
	} else {
	return true;
	}
	}

	static bool host_memory_backend_get_share(Object o, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(o);

	return backend->share;
	}

	static void host_memory_backend_set_share(Object o, bool value, Error *errp)
	{
	HostMemoryBackend *backend = MEMORY_BACKEND(o);

	if (host_memory_backend_mr_inited(backend)) {
	error_setg(errp, "cannot change property value");
	return;
	}
	backend->share = value;
	}

	static void
	host_memory_backend_class_init(ObjectClass oc, void data)
	{
	UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);

	ucc->complete = host_memory_backend_memory_complete;
	ucc->can_be_deleted = host_memory_backend_can_be_deleted;

	object_class_property_add_bool(oc, "merge",
	host_memory_backend_get_merge,
	host_memory_backend_set_merge, &error_abort);
	object_class_property_set_description(oc, "merge",
	"Mark memory as mergeable", &error_abort);
	object_class_property_add_bool(oc, "dump",
	host_memory_backend_get_dump,
	host_memory_backend_set_dump, &error_abort);
	object_class_property_set_description(oc, "dump",
	"Set to 'off' to exclude from core dump", &error_abort);
	object_class_property_add_bool(oc, "prealloc",
	host_memory_backend_get_prealloc,
	host_memory_backend_set_prealloc, &error_abort);
	object_class_property_set_description(oc, "prealloc",
	"Preallocate memory", &error_abort);
	object_class_property_add(oc, "size", "int",
	host_memory_backend_get_size,
	host_memory_backend_set_size,
	NULL, NULL, &error_abort);
	object_class_property_set_description(oc, "size",
	"Size of the memory region (ex: 500M)", &error_abort);
	object_class_property_add(oc, "host-nodes", "int",
	host_memory_backend_get_host_nodes,
	host_memory_backend_set_host_nodes,
	NULL, NULL, &error_abort);
	object_class_property_set_description(oc, "host-nodes",
	"Binds memory to the list of NUMA host nodes", &error_abort);
	object_class_property_add_enum(oc, "policy", "HostMemPolicy",
	&HostMemPolicy_lookup,
	host_memory_backend_get_policy,
	host_memory_backend_set_policy, &error_abort);
	object_class_property_set_description(oc, "policy",
	"Set the NUMA policy", &error_abort);
	object_class_property_add_bool(oc, "share",
	host_memory_backend_get_share, host_memory_backend_set_share,
	&error_abort);
	object_class_property_set_description(oc, "share",
	"Mark the memory as private to QEMU or shared", &error_abort);
	}

	static const TypeInfo host_memory_backend_info = {
	.name = TYPE_MEMORY_BACKEND,
	.parent = TYPE_OBJECT,
	.abstract = true,
	.class_size = sizeof(HostMemoryBackendClass),
	.class_init = host_memory_backend_class_init,
	.instance_size = sizeof(HostMemoryBackend),
	.instance_init = host_memory_backend_init,
	.interfaces = (InterfaceInfo[]) {
	{ TYPE_USER_CREATABLE },
	{ }
	}
	};

	static void register_types(void)
	{
	type_register_static(&host_memory_backend_info);
	}

	type_init(register_types);