[v3,1/4] os: add an ability to lock memory on_fault

Commit Message

Daniil Tatianin Dec. 11, 2024, 11:04 p.m. UTC

This will be used in the following commits to make it possible to only
lock memory on fault instead of right away.

Reviewed-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
Reviewed-by: Peter Xu <[e-mail]>
Signed-off-by: Daniil Tatianin <[e-mail]>
---
 include/sysemu/os-posix.h |  2 +-
 include/sysemu/os-win32.h |  3 ++-
 migration/postcopy-ram.c  |  2 +-
 os-posix.c                | 10 ++++++++--
 system/vl.c               |  2 +-
 5 files changed, 13 insertions(+), 6 deletions(-)

Patch

diff --git a/include/sysemu/os-posix.h b/include/sysemu/os-posix.h
index b881ac6c6f..ce5b3bccf8 100644
--- a/include/sysemu/os-posix.h
+++ b/include/sysemu/os-posix.h
@@ -53,7 +53,7 @@  bool os_set_runas(const char *user_id);
 void os_set_chroot(const char *path);
 void os_setup_limits(void);
 void os_setup_post(void);
-int os_mlock(void);
+int os_mlock(bool on_fault);
 
 /**
  * qemu_alloc_stack:
diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h
index b82a5d3ad9..cd61d69e10 100644
--- a/include/sysemu/os-win32.h
+++ b/include/sysemu/os-win32.h
@@ -123,8 +123,9 @@  static inline bool is_daemonized(void)
     return false;
 }
 
-static inline int os_mlock(void)
+static inline int os_mlock(bool on_fault)
 {
+    (void)on_fault;
     return -ENOSYS;
 }
 
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index a535fd2e30..36ec6a3d75 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -652,7 +652,7 @@  int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
     }
 
     if (enable_mlock) {
-        if (os_mlock() < 0) {
+        if (os_mlock(false) < 0) {
             error_report("mlock: %s", strerror(errno));
             /*
              * It doesn't feel right to fail at this point, we have a valid
diff --git a/os-posix.c b/os-posix.c
index 43f9a43f3f..0948128134 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -327,18 +327,24 @@  void os_set_line_buffering(void)
     setvbuf(stdout, NULL, _IOLBF, 0);
 }
 
-int os_mlock(void)
+int os_mlock(bool on_fault)
 {
 #ifdef HAVE_MLOCKALL
     int ret = 0;
+    int flags = MCL_CURRENT | MCL_FUTURE;
 
-    ret = mlockall(MCL_CURRENT | MCL_FUTURE);
+    if (on_fault) {
+        flags |= MCL_ONFAULT;
+    }
+
+    ret = mlockall(flags);
     if (ret < 0) {
         error_report("mlockall: %s", strerror(errno));
     }
 
     return ret;
 #else
+    (void)on_fault;
     return -ENOSYS;
 #endif
 }
diff --git a/system/vl.c b/system/vl.c
index 54998fdbc7..03819a80ef 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -793,7 +793,7 @@  static QemuOptsList qemu_run_with_opts = {
 static void realtime_init(void)
 {
     if (enable_mlock) {
-        if (os_mlock() < 0) {
+        if (os_mlock(false) < 0) {
             error_report("locking memory failed");
             exit(1);
         }