Add an option to simplify shared memory / vhost-user setup.
Currently, using vhost-user requires NUMA setup such as:
-m 4G -object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on
-numa node,memdev=mem
As there is no other way to allocate shareable RAM, afaik.
-mem-shared aims to have a simple way instead: -m 4G -mem-shared
Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
exec.c | 11 ++++++++++-
hw/core/numa.c | 16 +++++++++++++++-
include/sysemu/sysemu.h | 1 +
qemu-options.hx | 10 ++++++++++
vl.c | 4 ++++
5 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/exec.c b/exec.c
index ffdb518535..4e53937eaf 100644
--- a/exec.c
+++ b/exec.c
@@ -72,6 +72,10 @@
#include "qemu/mmap-alloc.h"
#endif
+#ifdef CONFIG_POSIX
+#include "qemu/memfd.h"
+#endif
+
#include "monitor/monitor.h"
//#define DEBUG_SUBPAGE
@@ -2347,7 +2351,12 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size,
MemoryRegion *mr,
bool created;
RAMBlock *block;
- fd = file_ram_open(mem_path, memory_region_name(mr), &created, errp);
+ if (mem_path) {
+ fd = file_ram_open(mem_path, memory_region_name(mr), &created, errp);
+ } else {
+ fd = qemu_memfd_open(mr->name, size,
+ F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL, errp);
+ }
if (fd < 0) {
return NULL;
}
diff --git a/hw/core/numa.c b/hw/core/numa.c
index e3332a984f..6f72cddb1c 100644
--- a/hw/core/numa.c
+++ b/hw/core/numa.c
@@ -493,7 +493,8 @@ static void allocate_system_memory_nonnuma(MemoryRegion
*mr, Object *owner,
if (mem_path) {
#ifdef __linux__
Error *err = NULL;
- memory_region_init_ram_from_file(mr, owner, name, ram_size, 0, 0,
+ memory_region_init_ram_from_file(mr, owner, name, ram_size, 0,
+ mem_shared ? RAM_SHARED : 0,
mem_path, &err);
if (err) {
error_report_err(err);
@@ -513,6 +514,19 @@ static void allocate_system_memory_nonnuma(MemoryRegion
*mr, Object *owner,
#else
fprintf(stderr, "-mem-path not supported on this host\n");
exit(1);
+#endif
+ } else if (mem_shared) {
+#ifdef CONFIG_POSIX
+ Error *err = NULL;
+ memory_region_init_ram_from_file(mr, owner, NULL, ram_size, 0,
+ RAM_SHARED, NULL, &err);
+ if (err) {
+ error_report_err(err);
+ exit(1);
+ }
+#else
+ fprintf(stderr, "-mem-shared not supported on this host\n");
+ exit(1);
#endif
} else {
memory_region_init_ram_nomigrate(mr, owner, name, ram_size,
&error_fatal);
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 80c57fdc4e..80db8465a9 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -55,6 +55,7 @@ extern bool enable_cpu_pm;
extern QEMUClockType rtc_clock;
extern const char *mem_path;
extern int mem_prealloc;
+extern int mem_shared;
#define MAX_OPTION_ROMS 16
typedef struct QEMUOptionRom {
diff --git a/qemu-options.hx b/qemu-options.hx
index 65c9473b73..4c69b03ad3 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -394,6 +394,16 @@ STEXI
Preallocate memory when using -mem-path.
ETEXI
+DEF("mem-shared", 0, QEMU_OPTION_mem_shared,
+ "-mem-shared allocate shared memory\n", QEMU_ARCH_ALL)
+STEXI
+@item -mem-shared
+@findex -mem-shared
+Allocate guest RAM with shared mapping. Whether the allocation is
+anonymous or not (with -mem-path), QEMU will allocate a shared memory that
+can be shared by unrelated processes, such as vhost-user backends.
+ETEXI
+
DEF("k", HAS_ARG, QEMU_OPTION_k,
"-k language use keyboard layout (for example 'fr' for French)\n",
QEMU_ARCH_ALL)
diff --git a/vl.c b/vl.c
index 6a65a64bfd..53b1155455 100644
--- a/vl.c
+++ b/vl.c
@@ -143,6 +143,7 @@ const char* keyboard_layout = NULL;
ram_addr_t ram_size;
const char *mem_path = NULL;
int mem_prealloc = 0; /* force preallocation of physical target memory */
+int mem_shared = 0;
bool enable_mlock = false;
bool enable_cpu_pm = false;
int nb_nics;
@@ -3172,6 +3173,9 @@ int main(int argc, char **argv, char **envp)
case QEMU_OPTION_mem_prealloc:
mem_prealloc = 1;
break;
+ case QEMU_OPTION_mem_shared:
+ mem_shared = 1;
+ break;
case QEMU_OPTION_d:
log_mask = optarg;
break;
--
2.24.0
