[PATCH V1 17/26] machine: memfd-alloc option

[Steve Sistare]

Allocate anonymous memory using memfd_create if the memfd-alloc machine
option is set.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 hw/core/machine.c   | 22 ++++++++++++++++++++++
 include/hw/boards.h |  1 +
 qemu-options.hx     |  6 ++++++
 system/memory.c     |  9 ++++++---
 system/physmem.c    | 18 +++++++++++++++++-
 system/trace-events |  1 +
 6 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 582c2df..9567b97 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -443,6 +443,20 @@ static void machine_set_mem_merge(Object *obj, bool value, 
Error **errp)
     ms->mem_merge = value;
 }
 
+static bool machine_get_memfd_alloc(Object *obj, Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    return ms->memfd_alloc;
+}
+
+static void machine_set_memfd_alloc(Object *obj, bool value, Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    ms->memfd_alloc = value;
+}
+
 static bool machine_get_usb(Object *obj, Error **errp)
 {
     MachineState *ms = MACHINE(obj);
@@ -1044,6 +1058,11 @@ static void machine_class_init(ObjectClass *oc, void 
*data)
     object_class_property_set_description(oc, "mem-merge",
         "Enable/disable memory merge support");
 
+    object_class_property_add_bool(oc, "memfd-alloc",
+        machine_get_memfd_alloc, machine_set_memfd_alloc);
+    object_class_property_set_description(oc, "memfd-alloc",
+        "Enable/disable allocating anonymous memory using memfd_create");
+
     object_class_property_add_bool(oc, "usb",
         machine_get_usb, machine_set_usb);
     object_class_property_set_description(oc, "usb",
@@ -1387,6 +1406,9 @@ static bool create_default_memdev(MachineState *ms, const 
char *path, Error **er
     if (!object_property_set_int(obj, "size", ms->ram_size, errp)) {
         goto out;
     }
+    if (!object_property_set_bool(obj, "share", ms->memfd_alloc, errp)) {
+        goto out;
+    }
     object_property_add_child(object_get_objects_root(), mc->default_ram_id,
                               obj);
     /* Ensure backend's memory region name is equal to mc->default_ram_id */
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 69c1ba4..96259c3 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -372,6 +372,7 @@ struct MachineState {
     bool dump_guest_core;
     bool mem_merge;
     bool require_guest_memfd;
+    bool memfd_alloc;
     bool usb;
     bool usb_disabled;
     char *firmware;
diff --git a/qemu-options.hx b/qemu-options.hx
index cf61f6b..f0dfda5 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -32,6 +32,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
     "                vmport=on|off|auto controls emulation of vmport (default: 
auto)\n"
     "                dump-guest-core=on|off include guest memory in a core 
dump (default=on)\n"
     "                mem-merge=on|off controls memory merge support (default: 
on)\n"
+    "                memfd-alloc=on|off controls allocating anonymous guest 
RAM using memfd_create (default: off)\n"
     "                aes-key-wrap=on|off controls support for AES key wrapping 
(default=on)\n"
     "                dea-key-wrap=on|off controls support for DEA key wrapping 
(default=on)\n"
     "                suppress-vmdesc=on|off disables self-describing migration 
(default=off)\n"
@@ -79,6 +80,11 @@ SRST
         supported by the host, de-duplicates identical memory pages
         among VMs instances (enabled by default).
 
+    ``memfd-alloc=on|off``
+        Enables or disables allocation of anonymous guest RAM using
+        memfd_create.  Any associated memory-backend objects are created with
+        share=on.  The memfd-alloc default is off.
+
     ``aes-key-wrap=on|off``
         Enables or disables AES key wrapping support on s390-ccw hosts.
         This feature controls whether AES wrapping keys will be created
diff --git a/system/memory.c b/system/memory.c
index 49f1cb2..ca04a0e 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -1552,8 +1552,9 @@ bool memory_region_init_ram_nomigrate(MemoryRegion *mr,
                                       uint64_t size,
                                       Error **errp)
 {
+    uint32_t flags = current_machine->memfd_alloc ? RAM_SHARED : 0;
     return memory_region_init_ram_flags_nomigrate(mr, owner, name,
-                                                  size, 0, errp);
+                                                  size, flags, errp);
 }
 
 bool memory_region_init_ram_flags_nomigrate(MemoryRegion *mr,
@@ -1713,8 +1714,9 @@ bool memory_region_init_rom_nomigrate(MemoryRegion *mr,
                                       uint64_t size,
                                       Error **errp)
 {
+    uint32_t flags = current_machine->memfd_alloc ? RAM_SHARED : 0;
     if (!memory_region_init_ram_flags_nomigrate(mr, owner, name,
-                                                size, 0, errp)) {
+                                                size, flags, errp)) {
          return false;
     }
     mr->readonly = true;
@@ -1731,6 +1733,7 @@ bool memory_region_init_rom_device_nomigrate(MemoryRegion 
*mr,
                                              Error **errp)
 {
     Error *err = NULL;
+    uint32_t flags = current_machine->memfd_alloc ? RAM_SHARED : 0;
     assert(ops);
     memory_region_init(mr, owner, name, size);
     mr->ops = ops;
@@ -1738,7 +1741,7 @@ bool memory_region_init_rom_device_nomigrate(MemoryRegion 
*mr,
     mr->terminates = true;
     mr->rom_device = true;
     mr->destructor = memory_region_destructor_ram;
-    mr->ram_block = qemu_ram_alloc(size, 0, mr, &err);
+    mr->ram_block = qemu_ram_alloc(size, flags, mr, &err);
     if (err) {
         mr->size = int128_zero();
         object_unparent(OBJECT(mr));
diff --git a/system/physmem.c b/system/physmem.c
index c736af5..36d97ec 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -45,6 +45,7 @@
 #include "qemu/qemu-print.h"
 #include "qemu/log.h"
 #include "qemu/memalign.h"
+#include "qemu/memfd.h"
 #include "exec/memory.h"
 #include "exec/ioport.h"
 #include "sysemu/dma.h"
@@ -1825,6 +1826,19 @@ static void *ram_block_alloc_host(RAMBlock *rb, Error 
**errp)
     if (xen_enabled()) {
         xen_ram_alloc(rb->offset, rb->max_length, mr, errp);
 
+    } else if (rb->flags & RAM_SHARED) {
+        if (rb->fd == -1) {
+            mr->align = QEMU_VMALLOC_ALIGN;
+            rb->fd = qemu_memfd_create(rb->idstr, rb->max_length + mr->align,
+                                       0, 0, 0, errp);
+        }
+        if (rb->fd >= 0) {
+            int mfd = rb->fd;
+            qemu_set_cloexec(mfd);
+            host = file_ram_alloc(rb, rb->max_length, mfd, false, 0, errp);
+            trace_qemu_anon_memfd_alloc(rb->idstr, rb->max_length, mfd, host);
+        }
+
     } else {
         host = qemu_anon_ram_alloc(rb->max_length, &mr->align,
                                    qemu_ram_is_shared(rb),
@@ -2106,8 +2120,10 @@ RAMBlock *qemu_ram_alloc_resizeable(ram_addr_t size, 
ram_addr_t maxsz,
                                                      void *host),
                                      MemoryRegion *mr, Error **errp)
 {
+    uint32_t flags = current_machine->memfd_alloc ? RAM_SHARED : 0;
+    flags |= RAM_RESIZEABLE;
     return qemu_ram_alloc_internal(size, maxsz, resized, NULL,
-                                   RAM_RESIZEABLE, mr, errp);
+                                   flags, mr, errp);
 }
 
 static void reclaim_ramblock(RAMBlock *block)
diff --git a/system/trace-events b/system/trace-events
index f0a80ba..0092734 100644
--- a/system/trace-events
+++ b/system/trace-events
@@ -41,3 +41,4 @@ dirtylimit_vcpu_execute(int cpu_index, int64_t sleep_time_us) 
"CPU[%d] sleep %"P
 
 # physmem.c
 ram_block_create(const char *name, uint32_t flags, int fd, size_t used_length, 
size_t max_length, size_t align) "%s, flags %u, fd %d, len %lu, maxlen %lu, 
align %lu"
+qemu_anon_memfd_alloc(const char *name, size_t size, int fd, void *ptr) "%s 
size %zu fd %d -> %p"
-- 
1.8.3.1