[PATCH v2 3/3] vhost, kcov: collect coverage from vhost_worker

[Andrey Konovalov]

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 <andreyk...@google.com>
---
 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..f44340b41494 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_common(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 = kcov_common_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);
-- 
2.24.0.rc0.303.g954a862665-goog