[PATCH 3/3] vhost, kcov: collect coverage from vhost_worker

[Andrey Konovalov <andreyknvl@xxxxxxxxxx>]

This patch adds kcov_remote_start()/kcov_remote_stop() annotations to the
vhost_worker() function, which is responsible for processing vhost works.
Since vhost_worker() threads are spawned per vhost device instance
the common kcov handle is used for kcov_remote_start()/stop() annotations
(see Documentation/dev-tools/kcov.rst for details). As the result kcov can
now be used to collect coverage from vhost worker threads.

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
---
 drivers/vhost/vhost.c | 6 ++++++
 drivers/vhost/vhost.h | 1 +
 2 files changed, 7 insertions(+)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 36ca2cf419bf..a5a557c4b67f 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -30,6 +30,7 @@
 #include <linux/sched/signal.h>
 #include <linux/interval_tree_generic.h>
 #include <linux/nospec.h>
+#include <linux/kcov.h>
 
 #include "vhost.h"
 
@@ -357,7 +358,9 @@ static int vhost_worker(void *data)
 		llist_for_each_entry_safe(work, work_next, node, node) {
 			clear_bit(VHOST_WORK_QUEUED, &work->flags);
 			__set_current_state(TASK_RUNNING);
+			kcov_remote_start(dev->kcov_handle);
 			work->fn(work);
+			kcov_remote_stop();
 			if (need_resched())
 				schedule();
 		}
@@ -546,6 +549,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
 
 	/* No owner, become one */
 	dev->mm = get_task_mm(current);
+	dev->kcov_handle = current->kcov_handle;
 	worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 	if (IS_ERR(worker)) {
 		err = PTR_ERR(worker);
@@ -571,6 +575,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
 	if (dev->mm)
 		mmput(dev->mm);
 	dev->mm = NULL;
+	dev->kcov_handle = 0;
 err_mm:
 	return err;
 }
@@ -682,6 +687,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
 	if (dev->worker) {
 		kthread_stop(dev->worker);
 		dev->worker = NULL;
+		dev->kcov_handle = 0;
 	}
 	if (dev->mm)
 		mmput(dev->mm);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index e9ed2722b633..a123fd70847e 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -173,6 +173,7 @@ struct vhost_dev {
 	int iov_limit;
 	int weight;
 	int byte_weight;
+	u64 kcov_handle;
 };
 
 bool vhost_exceeds_weight(struct vhost_virtqueue *vq, int pkts, int total_len);
-- 
2.23.0.866.gb869b98d4c-goog