Re: [PATCH 3/3] vhost, kcov: collect coverage from vhost_worker
From: Dmitry Vyukov <dvyukov@google.com>
Date: 2019-10-23 08:36:35
Also in:
kvm, linux-usb, lkml
On Tue, Oct 22, 2019 at 6:46 PM Andrey Konovalov [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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;
kcov_handle is not present in task_struct if !CONFIG_KCOV
Also this does not use KCOV_SUBSYSTEM_COMMON.
We discussed something along the following lines:
u64 kcov_remote_handle(u64 subsys, u64 id)
{
WARN_ON(subsys or id has wrong bits set).
return ...;
}
kcov_remote_handle(KCOV_SUBSYSTEM_USB, bus);
kcov_remote_handle(KCOV_SUBSYSTEM_COMMON, current->kcov_handle);
quoted hunk ↗ jump to hunk
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