prov/util: Add uffd user mode flag for kernels

Linux kernels 5.11 and later introduced a UFFD_USER_MODE_ONLY. When set, the userfaultfd object will only be able to handle page faults originated from the user space on the registered regions. If this is not set on kernels 5.11 or later, uffd will not work. Signed-off-by: Ian Ziemba <[email protected]>
ofiwg · Sep 13, 2024 · 27b977d · 27b977d
1 parent f8a5b20
commit 27b977d
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/prov/util/src/util_mem_monitor.c b/prov/util/src/util_mem_monitor.c
@@ -43,6 +43,9 @@
 #include <ofi_enosys.h>
 #include <rdma/fi_ext.h>
 
+#ifndef UFFD_USER_MODE_ONLY
+#define UFFD_USER_MODE_ONLY 0
+#endif
 
 pthread_mutex_t mm_lock = PTHREAD_MUTEX_INITIALIZER;
 pthread_mutex_t mm_state_lock = PTHREAD_MUTEX_INITIALIZER;
@@ -701,7 +704,8 @@ static int ofi_uffd_start(struct ofi_mem_monitor *monitor)
 	if (!num_page_sizes)
 		return -FI_ENODATA;
 
-	uffd.fd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
+	uffd.fd = syscall(__NR_userfaultfd,
+			  O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
 	if (uffd.fd < 0) {
 		FI_WARN(&core_prov, FI_LOG_MR,
 			"syscall/userfaultfd %s\n", strerror(errno));