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[PATCH v6 10/15] hostmem: Wire up RAM_NORESERVE via "reserve" property
From: |
David Hildenbrand |
Subject: |
[PATCH v6 10/15] hostmem: Wire up RAM_NORESERVE via "reserve" property |
Date: |
Wed, 21 Apr 2021 14:26:19 +0200 |
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 Linux currently supports clearing the flag (and support is checked at
runtime, depending on the setting of "/proc/sys/vm/overcommit_memory").
Windows and other POSIX systems will bail out with "reserve=false".
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.
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
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 | 32 ++++++++++++++++++++++++++++++++
include/sysemu/hostmem.h | 2 +-
qapi/qom.json | 4 ++++
6 files changed, 45 insertions(+), 6 deletions(-)
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index b683da9daf..9d550e53d4 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -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
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 93b5d1a4cf..f3436b623d 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -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, 0, errp);
g_free(name);
diff --git a/backends/hostmem-ram.c b/backends/hostmem-ram.c
index 741e701062..b8e55cdbd0 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 c6c1ff5b99..58fdc1b658 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -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 +522,10 @@ 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) if applicable");
/*
* 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 df5644723a..9ff5c16963 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 cd0e76d564..e9b86893a5 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)
+#
# @size: size of the memory region in bytes
#
# @x-use-canonical-path-for-ramblock-id: if true, the canoncial path is used
@@ -566,6 +569,7 @@
'*prealloc': 'bool',
'*prealloc-threads': 'uint32',
'*share': 'bool',
+ '*reserve': 'bool',
'size': 'size',
'*x-use-canonical-path-for-ramblock-id': 'bool' } }
--
2.30.2
- [PATCH v6 02/15] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve(), (continued)
- [PATCH v6 02/15] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve(), David Hildenbrand, 2021/04/21
- [PATCH v6 04/15] softmmu/memory: Pass ram_flags to qemu_ram_alloc_from_fd(), David Hildenbrand, 2021/04/21
- [PATCH v6 03/15] util/mmap-alloc: Factor out activating of memory to mmap_activate(), David Hildenbrand, 2021/04/21
- [PATCH v6 05/15] softmmu/memory: Pass ram_flags to memory_region_init_ram_shared_nomigrate(), David Hildenbrand, 2021/04/21
- [PATCH v6 06/15] softmmu/memory: Pass ram_flags to qemu_ram_alloc() and qemu_ram_alloc_internal(), David Hildenbrand, 2021/04/21
- [PATCH v6 07/15] util/mmap-alloc: Pass flags instead of separate bools to qemu_ram_mmap(), David Hildenbrand, 2021/04/21
- [PATCH v6 09/15] util/mmap-alloc: Support RAM_NORESERVE via MAP_NORESERVE under Linux, David Hildenbrand, 2021/04/21
- [PATCH v6 10/15] hostmem: Wire up RAM_NORESERVE via "reserve" property,
David Hildenbrand <=
- Re: [PATCH v6 10/15] hostmem: Wire up RAM_NORESERVE via "reserve" property, Markus Armbruster, 2021/04/23
- Re: [PATCH v6 10/15] hostmem: Wire up RAM_NORESERVE via "reserve" property, David Hildenbrand, 2021/04/23
- Re: [PATCH v6 10/15] hostmem: Wire up RAM_NORESERVE via "reserve" property, Markus Armbruster, 2021/04/23
- Re: [PATCH v6 10/15] hostmem: Wire up RAM_NORESERVE via "reserve" property, David Hildenbrand, 2021/04/23
- Re: [PATCH v6 10/15] hostmem: Wire up RAM_NORESERVE via "reserve" property, Markus Armbruster, 2021/04/23
[PATCH v6 08/15] memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap(), David Hildenbrand, 2021/04/21
[PATCH v6 11/15] qmp: Clarify memory backend properties returned via query-memdev, David Hildenbrand, 2021/04/21