kvm tools: Don't use ioeventfds if no KVM_CAP_IOEVENTFD

Check KVM_CAP_IOEVENTFD before using ioeventfds.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

builtin-run.c

@@ -932,7 +932,7 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
 
 	kvm->single_step = single_step;
 
-	ioeventfd__init();
+	ioeventfd__init(kvm);
 
 	max_cpus = kvm__max_cpus(kvm);
 	recommended_cpus = kvm__recommended_cpus(kvm);

include/kvm/ioeventfd.h

@@ -19,7 +19,7 @@ struct ioevent {
 	struct list_head	list;
 };
 
-void ioeventfd__init(void);
+void ioeventfd__init(struct kvm *kvm);
 void ioeventfd__start(void);
 void ioeventfd__add_event(struct ioevent *ioevent);
 void ioeventfd__del_event(u64 addr, u64 datamatch);

ioeventfd.c

@@ -18,9 +18,14 @@
 static struct	epoll_event events[IOEVENTFD_MAX_EVENTS];
 static int	epoll_fd;
 static LIST_HEAD(used_ioevents);
+static bool	ioeventfd_avail;
 
-void ioeventfd__init(void)
+void ioeventfd__init(struct kvm *kvm)
 {
+	ioeventfd_avail = kvm__has_cap(kvm, KVM_CAP_IOEVENTFD);
+	if (!ioeventfd_avail)
+		return;
+
 	epoll_fd = epoll_create(IOEVENTFD_MAX_EVENTS);
 	if (epoll_fd < 0)
 		die("Failed creating epoll fd");
@@ -33,6 +38,9 @@ void ioeventfd__add_event(struct ioevent *ioevent)
 	struct ioevent *new_ioevent;
 	int event;
 
+	if (!ioeventfd_avail)
+		return;
+
 	new_ioevent = malloc(sizeof(*new_ioevent));
 	if (new_ioevent == NULL)
 		die("Failed allocating memory for new ioevent");
@@ -68,6 +76,9 @@ void ioeventfd__del_event(u64 addr, u64 datamatch)
 	struct ioevent *ioevent;
 	u8 found = 0;
 
+	if (!ioeventfd_avail)
+		return;
+
 	list_for_each_entry(ioevent, &used_ioevents, list) {
 		if (ioevent->io_addr == addr) {
 			found = 1;
@@ -123,6 +134,9 @@ void ioeventfd__start(void)
 {
 	pthread_t thread;
 
+	if (!ioeventfd_avail)
+		return;
+
 	if (pthread_create(&thread, NULL, ioeventfd__thread, NULL) != 0)
 		die("Failed starting ioeventfd thread");
 }