@@ -40,6 +40,7 @@ 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) {
@@ -52,11 +53,11 @@ 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
@@ -55,6 +55,7 @@ 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, errp);
g_free(name);
@@ -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);
@@ -217,6 +217,11 @@ 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;
@@ -268,6 +273,7 @@ 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;
}
@@ -426,6 +432,28 @@ static void host_memory_backend_set_share(Object *o, bool value, Error **errp)
backend->share = value;
}
+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;
+}
+
static bool
host_memory_backend_get_use_canonical_path(Object *obj, Error **errp)
{
@@ -494,6 +522,11 @@ 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");
+ 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 under Linux) for the whole memory"
+ " backend, if supported by the OS.");
object_class_property_add_bool(oc, "x-use-canonical-path-for-ramblock-id",
host_memory_backend_get_use_canonical_path,
host_memory_backend_set_use_canonical_path);
@@ -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;
Let's provide a way to control the use of RAM_NORESERVE via memory backends using the "reserve" property which defaults to true (old behavior). Only POSIX supports setting the flag (and Linux support is checked at runtime, depending on the setting of "/proc/sys/vm/overcommit_memory"). Windows will bail out. The target use case is virtio-mem, which dynamically exposes memory inside a large, sparse memory area to the VM. This essentially allows avoiding to set "/proc/sys/vm/overcommit_memory == 0") when using virtio-mem and also supporting hugetlbfs in the future. Signed-off-by: David Hildenbrand <david@redhat.com> --- backends/hostmem-file.c | 11 ++++++----- backends/hostmem-memfd.c | 1 + backends/hostmem-ram.c | 1 + backends/hostmem.c | 33 +++++++++++++++++++++++++++++++++ include/sysemu/hostmem.h | 2 +- 5 files changed, 42 insertions(+), 6 deletions(-)