diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 5a0a2d93e0..38a47ad4ac 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -58,6 +58,7 @@ void *qemu_ram_get_host_addr(RAMBlock *rb);
 ram_addr_t qemu_ram_get_offset(RAMBlock *rb);
 ram_addr_t qemu_ram_get_used_length(RAMBlock *rb);
 bool qemu_ram_is_shared(RAMBlock *rb);
+bool qemu_ram_is_noreserve(RAMBlock *rb);
 bool qemu_ram_is_uf_zeroable(RAMBlock *rb);
 void qemu_ram_set_uf_zeroable(RAMBlock *rb);
 bool qemu_ram_is_migratable(RAMBlock *rb);
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 8879821371..7b700bdc33 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -155,6 +155,13 @@ typedef struct IOMMUTLBEvent {
  */
 #define RAM_UF_WRITEPROTECT (1 << 6)
 
+/*
+ * RAM is mmap-ed with MAP_NORESERVE. When set, reserving swap space (or huge
+ * pages if applicable) is skipped: will bail out if not supported. When not
+ * set, the OS might do the reservation, depending on OS support.
+ */
+#define RAM_NORESERVE (1 << 7)
+
 static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
                                        IOMMUNotifierFlag flags,
                                        hwaddr start, hwaddr end,
@@ -913,7 +920,7 @@ void memory_region_init_ram_nomigrate(MemoryRegion *mr,
  * @name: Region name, becomes part of RAMBlock name used in migration stream
  *        must be unique within any device
  * @size: size of the region.
- * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED.
+ * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_NORESERVE.
  * @errp: pointer to Error*, to store an error if it happens.
  *
  * Note that this function does not do anything to cause the data in the
@@ -967,7 +974,8 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr,
  * @size: size of the region.
  * @align: alignment of the region base address; if 0, the default alignment
  *         (getpagesize()) will be used.
- * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM.
+ * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
+ *             RAM_NORESERVE,
  * @path: the path in which to allocate the RAM.
  * @readonly: true to open @path for reading, false for read/write.
  * @errp: pointer to Error*, to store an error if it happens.
@@ -993,7 +1001,8 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
  * @owner: the object that tracks the region's reference count
  * @name: the name of the region.
  * @size: size of the region.
- * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM.
+ * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
+ *             RAM_NORESERVE.
  * @fd: the fd to mmap.
  * @offset: offset within the file referenced by fd
  * @errp: pointer to Error*, to store an error if it happens.
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 6d4513f8e2..551876bed0 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -104,7 +104,8 @@ long qemu_maxrampagesize(void);
  * Parameters:
  *  @size: the size in bytes of the ram block
  *  @mr: the memory region where the ram block is
- *  @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM.
+ *  @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
+ *              RAM_NORESERVE.
  *  @mem_path or @fd: specify the backing file or device
  *  @readonly: true to open @path for reading, false for read/write.
  *  @errp: pointer to Error*, to store an error if it happens
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 5ba89f5460..877d9a5eff 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -343,7 +343,8 @@ extern int daemon(int, int);
 int qemu_daemon(int nochdir, int noclose);
 void *qemu_try_memalign(size_t alignment, size_t size);
 void *qemu_memalign(size_t alignment, size_t size);
-void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared);
+void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared,
+                          bool noreserve);
 void qemu_vfree(void *ptr);
 void qemu_anon_ram_free(void *ptr, size_t size);
 
@@ -364,6 +365,12 @@ void qemu_anon_ram_free(void *ptr, size_t size);
  */
 #define QEMU_MAP_SYNC       (1 << 2)
 
+/*
+ * Use MAP_NORESERVE to skip reservation of swap space (or huge pages if
+ * applicable). Bail out if not supported/effective.
+ */
+#define QEMU_MAP_NORESERVE  (1 << 3)
+
 
 #define QEMU_MADV_INVALID -1
 
diff --git a/migration/ram.c b/migration/ram.c
index 40e78952ad..6a9c7d6e2f 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3320,8 +3320,7 @@ int colo_init_ram_cache(void)
     WITH_RCU_READ_LOCK_GUARD() {
         RAMBLOCK_FOREACH_NOT_IGNORED(block) {
             block->colo_cache = qemu_anon_ram_alloc(block->used_length,
-                                                    NULL,
-                                                    false);
+                                                    NULL, false, false);
             if (!block->colo_cache) {
                 error_report("%s: Can't alloc memory for COLO cache of block %s,"
                              "size 0x" RAM_ADDR_FMT, __func__, block->idstr,
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index d1a1a6b72e..608ba75d18 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -1584,6 +1584,7 @@ static void *file_ram_alloc(RAMBlock *block,
     qemu_map_flags = readonly ? QEMU_MAP_READONLY : 0;
     qemu_map_flags |= (block->flags & RAM_SHARED) ? QEMU_MAP_SHARED : 0;
     qemu_map_flags |= (block->flags & RAM_PMEM) ? QEMU_MAP_SYNC : 0;
+    qemu_map_flags |= (block->flags & RAM_NORESERVE) ? QEMU_MAP_NORESERVE : 0;
     area = qemu_ram_mmap(fd, memory, block->mr->align, qemu_map_flags, offset);
     if (area == MAP_FAILED) {
         error_setg_errno(errp, errno,
@@ -1704,6 +1705,11 @@ bool qemu_ram_is_shared(RAMBlock *rb)
     return rb->flags & RAM_SHARED;
 }
 
+bool qemu_ram_is_noreserve(RAMBlock *rb)
+{
+    return rb->flags & RAM_NORESERVE;
+}
+
 /* Note: Only set at the start of postcopy */
 bool qemu_ram_is_uf_zeroable(RAMBlock *rb)
 {
@@ -1931,6 +1937,7 @@ static void dirty_memory_extend(ram_addr_t old_ram_size,
 
 static void ram_block_add(RAMBlock *new_block, Error **errp)
 {
+    const bool noreserve = qemu_ram_is_noreserve(new_block);
     const bool shared = qemu_ram_is_shared(new_block);
     RAMBlock *block;
     RAMBlock *last_block = NULL;
@@ -1954,7 +1961,7 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
         } else {
             new_block->host = qemu_anon_ram_alloc(new_block->max_length,
                                                   &new_block->mr->align,
-                                                  shared);
+                                                  shared, noreserve);
             if (!new_block->host) {
                 error_setg_errno(errp, errno,
                                  "cannot set up guest memory '%s'",
@@ -2025,7 +2032,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
     int64_t file_size, file_align;
 
     /* Just support these ram flags by now. */
-    assert((ram_flags & ~(RAM_SHARED | RAM_PMEM)) == 0);
+    assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE)) == 0);
 
     if (xen_enabled()) {
         error_setg(errp, "-mem-path not supported with Xen");
@@ -2116,7 +2123,7 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
     RAMBlock *new_block;
     Error *local_err = NULL;
 
-    assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE)) == 0);
+    assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_NORESERVE)) == 0);
 
     size = HOST_PAGE_ALIGN(size);
     max_size = HOST_PAGE_ALIGN(max_size);
@@ -2151,7 +2158,7 @@ RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
 RAMBlock *qemu_ram_alloc(ram_addr_t size, uint32_t ram_flags,
                          MemoryRegion *mr, Error **errp)
 {
-    assert((ram_flags & ~RAM_SHARED) == 0);
+    assert((ram_flags & ~(RAM_SHARED | RAM_NORESERVE)) == 0);
     return qemu_ram_alloc_internal(size, size, NULL, NULL, ram_flags, mr, errp);
 }
 
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index 1ddc0e2a1e..d0cf4aaee5 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -20,6 +20,7 @@
 #include "qemu/osdep.h"
 #include "qemu/mmap-alloc.h"
 #include "qemu/host-utils.h"
+#include "qemu/error-report.h"
 
 #define HUGETLBFS_MAGIC       0x958458f6
 
@@ -121,6 +122,7 @@ static void *mmap_reserve(size_t size, int fd)
 static void *mmap_activate(void *ptr, size_t size, int fd,
                            uint32_t qemu_map_flags, off_t map_offset)
 {
+    const bool noreserve = qemu_map_flags & QEMU_MAP_NORESERVE;
     const bool readonly = qemu_map_flags & QEMU_MAP_READONLY;
     const bool shared = qemu_map_flags & QEMU_MAP_SHARED;
     const bool sync = qemu_map_flags & QEMU_MAP_SYNC;
@@ -129,6 +131,11 @@ static void *mmap_activate(void *ptr, size_t size, int fd,
     int flags = MAP_FIXED;
     void *activated_ptr;
 
+    if (noreserve) {
+        error_report("Skipping reservation of swap space is not supported");
+        return MAP_FAILED;
+    }
+
     flags |= fd == -1 ? MAP_ANONYMOUS : 0;
     flags |= shared ? MAP_SHARED : MAP_PRIVATE;
     if (shared && sync) {
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index c12108c6cb..5bbdebae0e 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -227,9 +227,11 @@ void *qemu_memalign(size_t alignment, size_t size)
 }
 
 /* alloc shared memory pages */
-void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared)
+void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
+                          bool noreserve)
 {
-    const uint32_t qemu_map_flags = shared ? QEMU_MAP_SHARED : 0;
+    const uint32_t qemu_map_flags = (shared ? QEMU_MAP_SHARED : 0) |
+                                    (noreserve ? QEMU_MAP_NORESERVE : 0);
     size_t align = QEMU_VMALLOC_ALIGN;
     void *ptr = qemu_ram_mmap(-1, size, align, qemu_map_flags, 0);
 
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index f68b8012bb..8cafe44179 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -39,6 +39,7 @@
 #include "trace.h"
 #include "qemu/sockets.h"
 #include "qemu/cutils.h"
+#include "qemu/error-report.h"
 #include <malloc.h>
 
 /* this must come after including "trace.h" */
@@ -77,10 +78,20 @@ static int get_allocation_granularity(void)
     return system_info.dwAllocationGranularity;
 }
 
-void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared)
+void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared,
+                          bool noreserve)
 {
     void *ptr;
 
+    if (noreserve) {
+        /*
+         * We need a MEM_COMMIT before accessing any memory in a MEM_RESERVE
+         * area; we cannot easily mimic POSIX MAP_NORESERVE semantics.
+         */
+        error_report("Skipping reservation of swap space is not supported.");
+        return NULL;
+    }
+
     ptr = VirtualAlloc(NULL, size, MEM_COMMIT, PAGE_READWRITE);
     trace_qemu_anon_ram_alloc(size, ptr);
 
