diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 9b1b9f0a56043dc5788826c16fb9519f9fdf8370..cd038024fae3c056cc2f01e4654c2e962bb0336c 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -39,6 +39,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
object_get_typename(OBJECT(backend)));
#else
HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
+ uint32_t ram_flags;
gchar *name;
if (!backend->size) {
@@ -51,11 +52,11 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
}
name = host_memory_backend_get_name(backend);
- memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
- name,
- backend->size, fb->align,
- (backend->share ? RAM_SHARED : 0) |
- (fb->is_pmem ? RAM_PMEM : 0),
+ ram_flags = backend->share ? RAM_SHARED : 0;
+ ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
+ ram_flags |= fb->is_pmem ? RAM_PMEM : 0;
+ memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), name,
+ backend->size, fb->align, ram_flags,
fb->mem_path, fb->readonly, errp);
g_free(name);
#endif
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 3076da146d9af59ca4f9a2f348db4f49e8a95124..3fc85c3db81bb71176cdfe65dbf0643e1504355b 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -54,6 +54,7 @@ memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
name = host_memory_backend_get_name(backend);
ram_flags = backend->share ? RAM_SHARED : 0;
+ ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name,
backend->size, ram_flags, fd, 0, errp);
g_free(name);
diff --git a/backends/hostmem-ram.c b/backends/hostmem-ram.c
index 741e7010628958f51683d2d627429f5a25d13749..b8e55cdbd0f89078b01bb1575416173ce909526b 100644
--- a/backends/hostmem-ram.c
+++ b/backends/hostmem-ram.c
@@ -29,6 +29,7 @@ ram_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
name = host_memory_backend_get_name(backend);
ram_flags = backend->share ? RAM_SHARED : 0;
+ ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
memory_region_init_ram_flags_nomigrate(&backend->mr, OBJECT(backend), name,
backend->size, ram_flags, errp);
g_free(name);
diff --git a/backends/hostmem.c b/backends/hostmem.c
index aab3de84083e79ce09a3d207162c2fd8584e8ae3..4c05862ed5a89059f1dbca8b9285692a413dfa36 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -216,6 +216,11 @@ static void host_memory_backend_set_prealloc(Object *obj, bool value,
Error *local_err = NULL;
HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+ if (!backend->reserve && value) {
+ error_setg(errp, "'prealloc=on' and 'reserve=off' are incompatible");
+ return;
+ }
+
if (!host_memory_backend_mr_inited(backend)) {
backend->prealloc = value;
return;
@@ -267,6 +272,7 @@ static void host_memory_backend_init(Object *obj)
/* TODO: convert access to globals to compat properties */
backend->merge = machine_mem_merge(machine);
backend->dump = machine_dump_guest_core(machine);
+ backend->reserve = true;
backend->prealloc_threads = 1;
}
@@ -425,6 +431,30 @@ static void host_memory_backend_set_share(Object *o, bool value, Error **errp)
backend->share = value;
}
+#ifdef CONFIG_LINUX
+static bool host_memory_backend_get_reserve(Object *o, Error **errp)
+{
+ HostMemoryBackend *backend = MEMORY_BACKEND(o);
+
+ return backend->reserve;
+}
+
+static void host_memory_backend_set_reserve(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;
+ }
+ if (backend->prealloc && !value) {
+ error_setg(errp, "'prealloc=on' and 'reserve=off' are incompatible");
+ return;
+ }
+ backend->reserve = value;
+}
+#endif /* CONFIG_LINUX */
+
static bool
host_memory_backend_get_use_canonical_path(Object *obj, Error **errp)
{
@@ -493,6 +523,12 @@ host_memory_backend_class_init(ObjectClass *oc, void *data)
host_memory_backend_get_share, host_memory_backend_set_share);
object_class_property_set_description(oc, "share",
"Mark the memory as private to QEMU or shared");
+#ifdef CONFIG_LINUX
+ object_class_property_add_bool(oc, "reserve",
+ host_memory_backend_get_reserve, host_memory_backend_set_reserve);
+ object_class_property_set_description(oc, "reserve",
+ "Reserve swap space (or huge pages) if applicable");
+#endif /* CONFIG_LINUX */
/*
* Do not delete/rename option. This option must be considered stable
* (as if it didn't have the 'x-' prefix including deprecation period) as
diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index df5644723a39523a1a193a828909cfe148bcc1fc..9ff5c16963f0bf2ad6386646caa6945d92764c99 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -64,7 +64,7 @@ struct HostMemoryBackend {
/* protected */
uint64_t size;
bool merge, dump, use_canonical_path;
- bool prealloc, is_mapped, share;
+ bool prealloc, is_mapped, share, reserve;
uint32_t prealloc_threads;
DECLARE_BITMAP(host_nodes, MAX_NODES + 1);
HostMemPolicy policy;
diff --git a/qapi/qom.json b/qapi/qom.json
index f7ef30f940c31334327ccbb427ddb5a6efbd8221..652be317b8b5d76d88f3b61a701800f27ac29a41 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -545,6 +545,9 @@
# @share: if false, the memory is private to QEMU; if true, it is shared
# (default: false)
#
+# @reserve: if true, reserve swap space (or huge pages) if applicable
+# (default: true) (since 6.1)
+#
# @size: size of the memory region in bytes
#
# @x-use-canonical-path-for-ramblock-id: if true, the canoncial path is used
@@ -556,6 +559,12 @@
# false generally, but true for machine
# types <= 4.0)
#
+# Note: prealloc=true and reserve=false cannot be set at the same time. With
+# reserve=true, the behavior depends on the operating system: for example,
+# Linux will not reserve swap space for shared file mappings --
+# "not applicable". In contrast, reserve=false will bail out if it cannot
+# be configured accordingly.
+#
# Since: 2.1
##
{ 'struct': 'MemoryBackendProperties',
@@ -566,6 +575,7 @@
'*prealloc': 'bool',
'*prealloc-threads': 'uint32',
'*share': 'bool',
+ '*reserve': 'bool',
'size': 'size',
'*x-use-canonical-path-for-ramblock-id': 'bool' } }