thr3ads.net - Virtualization - [PATCH V4 02/12] vhost, vhost-net: add helper to check if vq has work [Nov 2021]

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Mike Christie

2021-Nov-04 19:04 UTC

[PATCH V4 00/12] vhost: multiple worker support

The following patches apply over linus's tree and this patchset

https://lore.kernel.org/all/20211007214448.6282-1-michael.christie at
oracle.com/

which allows us to check the vhost owner thread's RLIMITs.

The patches allow us to support multiple vhost workers per device. The
design is a modified version of Stefan's original idea where userspace has
the kernel create a worker and we pass back the pid. In this version, V4,
instead of passing the pid between user/kernel space we use a worker_id
which is just an integer managed by the vhost driver and we allow userspace
to create and free workers and then attach them to virtqueues at setup time
or while IO is running.

All review comments from the past reviews should be handled. If I didn't
reply to a review comment, I agreed with the comment and should have
handled it in this posting. Let me know if I missed one.

Results:
--------

fio jobs        1       2       4       8       12      16
----------------------------------------------------------
1 worker        84k    492k    510k    -       -       -
worker per vq   184k   380k    744k    1422k   2256k   2434k

Notes:
0. This used a simple fio command:

fio --filename=/dev/sdb  --direct=1 --rw=randrw --bs=4k \
--ioengine=libaio --iodepth=128  --numjobs=$JOBS_ABOVE

and I used a VM with 16 vCPUs and 16 virtqueues.

1. The patches were tested with emulate_pr=0 and these patches:

https://lore.kernel.org/all/yq1tuhge4bg.fsf at ca-mkp.ca.oracle.com/t/

which are in mkp's scsi branches for the next kernel. They fix the perf
issues where IOPs dropped at 12 vqs/jobs.

2. Because we have a hard limit of 1024 cmds, if the num jobs * iodepth
was greater than 1024, I would decrease iodepth. So 12 jobs used 85 cmds,
and 16 used 64.

3. The perf issue above at 2 jobs is because when we only have 1 worker
we execute more cmds per vhost_work due to all vqs funneling to one worker.
This results in less context switches and better batching without having to
tweak any settings. I'm working on patches to add back batching during lio
completion and do polling on the submission side.

We will still want the threading patches, because if we batch at the fio
level plus use the vhost theading patches, we can see a big boost like
below. So hopefully doing it at the kernel will allow apps to just work
without having to be smart like fio.

fio using io_uring and batching with the iodepth_batch* settings:

fio jobs        1       2       4       8       12      16
-------------------------------------------------------------
1 worker        494k    520k    -       -       -       -
worker per vq   496k    878k    1542k   2436k   2304k   2590k

V4:
- fix vhost-sock VSOCK_VQ_RX use.
- name functions called directly by an ioctl cmd's to match the ioctl cmd.
- break up VHOST_SET_VRING_WORKER into a new, free and attach cmd.
- document worker lifetime, and cgroup, namespace, mm, rlimit
inheritance, and make it clear we currently only support sharing within
the device.
- add support to attach workers while IO is running so that config can
be done post setup.
- instead of passing a pid_t of the kernel thread, use a int allocated
by the vhost layer with an idr.

V3:
- fully convert vhost code to use vq based APIs instead of leaving it
half per dev and half per vq.
- rebase against kernel worker API.
- Drop delayed worker creation. We always create the default worker at
VHOST_SET_OWNER time. Userspace can create and bind workers after that.

V2:
- change loop that we take a refcount to the worker in
- replaced pid == -1 with define.
- fixed tabbing/spacing coding style issue
- use hash instead of list to lookup workers.
- I dropped the patch that added an ioctl cmd to get a vq's worker's
pid. I saw we might do a generic netlink interface instead.

Mike Christie

2021-Nov-04 19:04 UTC

head link

[PATCH V4 01/12] vhost: add vhost_worker pointer to vhost_virtqueue

This patchset allows userspace to map vqs to different workers. This
patch adds a worker pointer to the vq so we can store that info.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/vhost.c | 24 +++++++++++++-----------
 drivers/vhost/vhost.h |  1 +
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 9aa04fcdf210..9b4e7d74dab4 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -496,6 +496,7 @@ void vhost_dev_init(struct vhost_dev *dev,
 		vq->log = NULL;
 		vq->indirect = NULL;
 		vq->heads = NULL;
+		vq->worker = NULL;
 		vq->dev = dev;
 		mutex_init(&vq->mutex);
 		vhost_vq_reset(dev, vq);
@@ -574,15 +575,14 @@ static void vhost_worker_free(struct vhost_dev *dev)
 	kfree(worker);
 }
 
-static int vhost_worker_create(struct vhost_dev *dev)
+static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
 {
 	struct vhost_worker *worker;
 	struct task_struct *task;
-	int ret;
 
 	worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
 	if (!worker)
-		return -ENOMEM;
+		return NULL;
 
 	dev->worker = worker;
 	worker->kcov_handle = kcov_common_handle();
@@ -594,25 +594,24 @@ static int vhost_worker_create(struct vhost_dev *dev)
 	 */
 	task = kernel_worker(vhost_worker, worker, NUMA_NO_NODE, CLONE_FS,
 			     KERN_WORKER_NO_FILES | KERN_WORKER_SIG_IGN);
-	if (IS_ERR(task)) {
-		ret = PTR_ERR(task);
+	if (IS_ERR(task))
 		goto free_worker;
-	}
 
 	worker->task = task;
 	kernel_worker_start(task, "vhost-%d", current->pid);
-	return 0;
+	return worker;
 
 free_worker:
 	kfree(worker);
 	dev->worker = NULL;
-	return ret;
+	return NULL;
 }
 
 /* Caller should have device mutex */
 long vhost_dev_set_owner(struct vhost_dev *dev)
 {
-	int err;
+	struct vhost_worker *worker;
+	int err, i;
 
 	/* Is there an owner already? */
 	if (vhost_dev_has_owner(dev)) {
@@ -623,9 +622,12 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
 	vhost_attach_mm(dev);
 
 	if (dev->use_worker) {
-		err = vhost_worker_create(dev);
-		if (err)
+		worker = vhost_worker_create(dev);
+		if (!worker)
 			goto err_worker;
+
+		for (i = 0; i < dev->nvqs; i++)
+			dev->vqs[i]->worker = worker;
 	}
 
 	err = vhost_dev_alloc_iovecs(dev);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 09748694cb66..7ee38b4a2807 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -80,6 +80,7 @@ struct vhost_vring_call {
 /* The virtqueue structure describes a queue attached to a device. */
 struct vhost_virtqueue {
 	struct vhost_dev *dev;
+	struct vhost_worker *worker;
 
 	/* The actual ring of buffers. */
 	struct mutex mutex;
-- 
2.25.1

Mike Christie

2021-Nov-04 19:04 UTC

head link

[PATCH V4 02/12] vhost, vhost-net: add helper to check if vq has work

This adds a helper to check if a vq has work pending and converts
vhost-net to use it.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/net.c   | 2 +-
 drivers/vhost/vhost.c | 6 +++---
 drivers/vhost/vhost.h | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 28ef323882fb..6c4b2b2158bb 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -543,7 +543,7 @@ static void vhost_net_busy_poll(struct vhost_net *net,
 	endtime = busy_clock() + busyloop_timeout;
 
 	while (vhost_can_busy_poll(endtime)) {
-		if (vhost_has_work(&net->dev)) {
+		if (vhost_vq_has_work(vq)) {
 			*busyloop_intr = true;
 			break;
 		}
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 9b4e7d74dab4..f6bfa1c481df 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -269,11 +269,11 @@ void vhost_work_queue(struct vhost_dev *dev, struct
vhost_work *work)
 EXPORT_SYMBOL_GPL(vhost_work_queue);
 
 /* A lockless hint for busy polling code to exit the loop */
-bool vhost_has_work(struct vhost_dev *dev)
+bool vhost_vq_has_work(struct vhost_virtqueue *vq)
 {
-	return dev->worker &&
!llist_empty(&dev->worker->work_list);
+	return vq->worker &&
!llist_empty(&vq->worker->work_list);
 }
-EXPORT_SYMBOL_GPL(vhost_has_work);
+EXPORT_SYMBOL_GPL(vhost_vq_has_work);
 
 void vhost_poll_queue(struct vhost_poll *poll)
 {
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 7ee38b4a2807..37989518a07c 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -50,7 +50,6 @@ struct vhost_poll {
 
 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn);
 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
-bool vhost_has_work(struct vhost_dev *dev);
 
 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
 		     __poll_t mask, struct vhost_dev *dev);
@@ -200,6 +199,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *,
 		      struct vhost_log *log, unsigned int *log_num);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
+bool vhost_vq_has_work(struct vhost_virtqueue *vq);
 bool vhost_vq_is_setup(struct vhost_virtqueue *vq);
 int vhost_vq_init_access(struct vhost_virtqueue *);
 int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len);
-- 
2.25.1

Mike Christie

2021-Nov-04 19:04 UTC

head link

[PATCH V4 03/12] vhost: take worker or vq instead of dev for queueing

This patch has the core work queueing function take a worker for when we
support multiple workers. It also adds a helper that takes a vq during
queueing so modules can control which vq/worker to queue work on.

This temp leaves vhost_work_queue. It will be removed when the drivers
are converted in the next patches.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/vhost.c | 44 +++++++++++++++++++++++++++----------------
 drivers/vhost/vhost.h |  1 +
 2 files changed, 29 insertions(+), 16 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index f6bfa1c481df..f2c6981297d0 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -230,6 +230,34 @@ void vhost_poll_stop(struct vhost_poll *poll)
 }
 EXPORT_SYMBOL_GPL(vhost_poll_stop);
 
+static void vhost_work_queue_on(struct vhost_worker *worker,
+				struct vhost_work *work)
+{
+	if (!worker)
+		return;
+
+	if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
+		/* We can only add the work to the list after we're
+		 * sure it was not in the list.
+		 * test_and_set_bit() implies a memory barrier.
+		 */
+		llist_add(&work->node, &worker->work_list);
+		wake_up_process(worker->task);
+	}
+}
+
+void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
+{
+	vhost_work_queue_on(dev->worker, work);
+}
+EXPORT_SYMBOL_GPL(vhost_work_queue);
+
+void vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work)
+{
+	vhost_work_queue_on(vq->worker, work);
+}
+EXPORT_SYMBOL_GPL(vhost_vq_work_queue);
+
 void vhost_work_dev_flush(struct vhost_dev *dev)
 {
 	struct vhost_flush_struct flush;
@@ -252,22 +280,6 @@ void vhost_poll_flush(struct vhost_poll *poll)
 }
 EXPORT_SYMBOL_GPL(vhost_poll_flush);
 
-void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
-{
-	if (!dev->worker)
-		return;
-
-	if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
-		/* We can only add the work to the list after we're
-		 * sure it was not in the list.
-		 * test_and_set_bit() implies a memory barrier.
-		 */
-		llist_add(&work->node, &dev->worker->work_list);
-		wake_up_process(dev->worker->task);
-	}
-}
-EXPORT_SYMBOL_GPL(vhost_work_queue);
-
 /* A lockless hint for busy polling code to exit the loop */
 bool vhost_vq_has_work(struct vhost_virtqueue *vq)
 {
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 37989518a07c..8f209d1c8890 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -199,6 +199,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *,
 		      struct vhost_log *log, unsigned int *log_num);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
+void vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work);
 bool vhost_vq_has_work(struct vhost_virtqueue *vq);
 bool vhost_vq_is_setup(struct vhost_virtqueue *vq);
 int vhost_vq_init_access(struct vhost_virtqueue *);
-- 
2.25.1

Mike Christie

2021-Nov-04 19:04 UTC

head link

[PATCH V4 04/12] vhost: take worker or vq instead of dev for flushing

This patch has the core work flush function take a worker for when we
support multiple workers. It also adds a helper that takes a vq during
flushing so modules can control which vq/worker to flush.

This temp leaves vhost_work_dev_flush. It will be removed when the drivers
are converted in the next patches.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/vhost.c | 30 +++++++++++++++++++++---------
 drivers/vhost/vhost.h |  1 +
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index f2c6981297d0..e4d765f6c821 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -246,6 +246,26 @@ static void vhost_work_queue_on(struct vhost_worker
*worker,
 	}
 }
 
+static void vhost_work_flush_on(struct vhost_worker *worker)
+{
+	struct vhost_flush_struct flush;
+
+	if (!worker)
+		return;
+
+	init_completion(&flush.wait_event);
+	vhost_work_init(&flush.work, vhost_flush_work);
+
+	vhost_work_queue_on(worker, &flush.work);
+	wait_for_completion(&flush.wait_event);
+}
+
+void vhost_vq_work_flush(struct vhost_virtqueue *vq)
+{
+	vhost_work_flush_on(vq->worker);
+}
+EXPORT_SYMBOL_GPL(vhost_vq_work_flush);
+
 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 {
 	vhost_work_queue_on(dev->worker, work);
@@ -260,15 +280,7 @@ EXPORT_SYMBOL_GPL(vhost_vq_work_queue);
 
 void vhost_work_dev_flush(struct vhost_dev *dev)
 {
-	struct vhost_flush_struct flush;
-
-	if (dev->worker) {
-		init_completion(&flush.wait_event);
-		vhost_work_init(&flush.work, vhost_flush_work);
-
-		vhost_work_queue(dev, &flush.work);
-		wait_for_completion(&flush.wait_event);
-	}
+	vhost_work_flush_on(dev->worker);
 }
 EXPORT_SYMBOL_GPL(vhost_work_dev_flush);
 
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 8f209d1c8890..a985caa35633 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -199,6 +199,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *,
 		      struct vhost_log *log, unsigned int *log_num);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
+void vhost_vq_work_flush(struct vhost_virtqueue *vq);
 void vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work);
 bool vhost_vq_has_work(struct vhost_virtqueue *vq);
 bool vhost_vq_is_setup(struct vhost_virtqueue *vq);
-- 
2.25.1

Mike Christie

2021-Nov-04 19:04 UTC

head link

[PATCH V4 05/12] vhost: convert poll work to be vq based

This has the drivers pass in their poll to vq mapping and then converts
the core poll code to use the vq based helpers.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/net.c   |  6 ++++--
 drivers/vhost/vhost.c | 10 ++++++----
 drivers/vhost/vhost.h |  4 +++-
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 6c4b2b2158bb..2e1abab45f3c 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1339,8 +1339,10 @@ static int vhost_net_open(struct inode *inode, struct
file *f)
 		       VHOST_NET_PKT_WEIGHT, VHOST_NET_WEIGHT, true,
 		       NULL);
 
-	vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, EPOLLOUT, dev);
-	vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, EPOLLIN, dev);
+	vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, EPOLLOUT, dev,
+			vqs[VHOST_NET_VQ_TX]);
+	vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, EPOLLIN, dev,
+			vqs[VHOST_NET_VQ_RX]);
 
 	f->private_data = n;
 	n->page_frag.page = NULL;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index e4d765f6c821..c84024afefff 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -186,13 +186,15 @@ EXPORT_SYMBOL_GPL(vhost_work_init);
 
 /* Init poll structure */
 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
-		     __poll_t mask, struct vhost_dev *dev)
+		     __poll_t mask, struct vhost_dev *dev,
+		     struct vhost_virtqueue *vq)
 {
 	init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
 	init_poll_funcptr(&poll->table, vhost_poll_func);
 	poll->mask = mask;
 	poll->dev = dev;
 	poll->wqh = NULL;
+	poll->vq = vq;
 
 	vhost_work_init(&poll->work, fn);
 }
@@ -288,7 +290,7 @@ EXPORT_SYMBOL_GPL(vhost_work_dev_flush);
  * locks that are also used by the callback. */
 void vhost_poll_flush(struct vhost_poll *poll)
 {
-	vhost_work_dev_flush(poll->dev);
+	vhost_vq_work_flush(poll->vq);
 }
 EXPORT_SYMBOL_GPL(vhost_poll_flush);
 
@@ -301,7 +303,7 @@ EXPORT_SYMBOL_GPL(vhost_vq_has_work);
 
 void vhost_poll_queue(struct vhost_poll *poll)
 {
-	vhost_work_queue(poll->dev, &poll->work);
+	vhost_vq_work_queue(poll->vq, &poll->work);
 }
 EXPORT_SYMBOL_GPL(vhost_poll_queue);
 
@@ -526,7 +528,7 @@ void vhost_dev_init(struct vhost_dev *dev,
 		vhost_vq_reset(dev, vq);
 		if (vq->handle_kick)
 			vhost_poll_init(&vq->poll, vq->handle_kick,
-					EPOLLIN, dev);
+					EPOLLIN, dev, vq);
 	}
 }
 EXPORT_SYMBOL_GPL(vhost_dev_init);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index a985caa35633..d9650da2be2c 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -46,13 +46,15 @@ struct vhost_poll {
 	struct vhost_work	work;
 	__poll_t		mask;
 	struct vhost_dev	*dev;
+	struct vhost_virtqueue	*vq;
 };
 
 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn);
 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
 
 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
-		     __poll_t mask, struct vhost_dev *dev);
+		     __poll_t mask, struct vhost_dev *dev,
+		     struct vhost_virtqueue *vq);
 int vhost_poll_start(struct vhost_poll *poll, struct file *file);
 void vhost_poll_stop(struct vhost_poll *poll);
 void vhost_poll_flush(struct vhost_poll *poll);
-- 
2.25.1

Mike Christie

2021-Nov-04 19:04 UTC

head link

[PATCH V4 06/12] vhost-sock: convert to vq helpers

Convert from vhost dev based helpers to vq ones.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/vsock.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 938aefbc75ec..0c9681e120de 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -300,7 +300,7 @@ vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
 	list_add_tail(&pkt->list, &vsock->send_pkt_list);
 	spin_unlock_bh(&vsock->send_pkt_list_lock);
 
-	vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);
+	vhost_vq_work_queue(&vsock->vqs[VSOCK_VQ_RX],
&vsock->send_pkt_work);
 
 	rcu_read_unlock();
 	return len;
@@ -612,7 +612,7 @@ static int vhost_vsock_start(struct vhost_vsock *vsock)
 	/* Some packets may have been queued before the device was started,
 	 * let's kick the send worker to send them.
 	 */
-	vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);
+	vhost_vq_work_queue(&vsock->vqs[VSOCK_VQ_RX],
&vsock->send_pkt_work);
 
 	mutex_unlock(&vsock->dev.mutex);
 	return 0;
@@ -712,7 +712,9 @@ static void vhost_vsock_flush(struct vhost_vsock *vsock)
 	for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++)
 		if (vsock->vqs[i].handle_kick)
 			vhost_poll_flush(&vsock->vqs[i].poll);
-	vhost_work_dev_flush(&vsock->dev);
+
+	vhost_vq_work_flush(&vsock->vqs[VSOCK_VQ_TX]);
+	vhost_vq_work_flush(&vsock->vqs[VSOCK_VQ_RX]);
 }
 
 static void vhost_vsock_reset_orphans(struct sock *sk)
-- 
2.25.1

Mike Christie

2021-Nov-04 19:04 UTC

head link

[PATCH V4 07/12] vhost-scsi: make SCSI cmd completion per vq

This patch separates the scsi cmd completion code paths so we can complete
cmds based on their vq instead of having all cmds complete on the same
worker/CPU. This will be useful with the next patches that allow us to
create mulitple worker threads and bind them to different vqs, so we can
have completions running on different threads/CPUs.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
---
 drivers/vhost/scsi.c | 48 +++++++++++++++++++++++---------------------
 1 file changed, 25 insertions(+), 23 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 532e204f2b1b..0d85ddb68420 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -164,6 +164,7 @@ enum {
 
 struct vhost_scsi_virtqueue {
 	struct vhost_virtqueue vq;
+	struct vhost_scsi *vs;
 	/*
 	 * Reference counting for inflight reqs, used for flush operation. At
 	 * each time, one reference tracks new commands submitted, while we
@@ -178,6 +179,9 @@ struct vhost_scsi_virtqueue {
 	struct vhost_scsi_cmd *scsi_cmds;
 	struct sbitmap scsi_tags;
 	int max_cmds;
+
+	struct vhost_work completion_work;
+	struct llist_head completion_list;
 };
 
 struct vhost_scsi {
@@ -188,9 +192,6 @@ struct vhost_scsi {
 	struct vhost_dev dev;
 	struct vhost_scsi_virtqueue vqs[VHOST_SCSI_MAX_VQ];
 
-	struct vhost_work vs_completion_work; /* cmd completion work item */
-	struct llist_head vs_completion_list; /* cmd completion queue */
-
 	struct vhost_work vs_event_work; /* evt injection work item */
 	struct llist_head vs_event_list; /* evt injection queue */
 
@@ -365,10 +366,11 @@ static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)
 	} else {
 		struct vhost_scsi_cmd *cmd = container_of(se_cmd,
 					struct vhost_scsi_cmd, tvc_se_cmd);
-		struct vhost_scsi *vs = cmd->tvc_vhost;
+		struct vhost_scsi_virtqueue *svq =  container_of(cmd->tvc_vq,
+					struct vhost_scsi_virtqueue, vq);
 
-		llist_add(&cmd->tvc_completion_list, &vs->vs_completion_list);
-		vhost_work_queue(&vs->dev, &vs->vs_completion_work);
+		llist_add(&cmd->tvc_completion_list, &svq->completion_list);
+		vhost_vq_work_queue(&svq->vq, &svq->completion_work);
 	}
 }
 
@@ -531,18 +533,17 @@ static void vhost_scsi_evt_work(struct vhost_work *work)
  */
 static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
 {
-	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
-					vs_completion_work);
-	DECLARE_BITMAP(signal, VHOST_SCSI_MAX_VQ);
+	struct vhost_scsi_virtqueue *svq = container_of(work,
+				struct vhost_scsi_virtqueue, completion_work);
 	struct virtio_scsi_cmd_resp v_rsp;
 	struct vhost_scsi_cmd *cmd, *t;
 	struct llist_node *llnode;
 	struct se_cmd *se_cmd;
 	struct iov_iter iov_iter;
-	int ret, vq;
+	bool signal = false;
+	int ret;
 
-	bitmap_zero(signal, VHOST_SCSI_MAX_VQ);
-	llnode = llist_del_all(&vs->vs_completion_list);
+	llnode = llist_del_all(&svq->completion_list);
 	llist_for_each_entry_safe(cmd, t, llnode, tvc_completion_list) {
 		se_cmd = &cmd->tvc_se_cmd;
 
@@ -562,21 +563,16 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work
*work)
 			      cmd->tvc_in_iovs, sizeof(v_rsp));
 		ret = copy_to_iter(&v_rsp, sizeof(v_rsp), &iov_iter);
 		if (likely(ret == sizeof(v_rsp))) {
-			struct vhost_scsi_virtqueue *q;
+			signal = true;
 			vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
-			q = container_of(cmd->tvc_vq, struct vhost_scsi_virtqueue, vq);
-			vq = q - vs->vqs;
-			__set_bit(vq, signal);
 		} else
 			pr_err("Faulted on virtio_scsi_cmd_resp\n");
 
 		vhost_scsi_release_cmd_res(se_cmd);
 	}
 
-	vq = -1;
-	while ((vq = find_next_bit(signal, VHOST_SCSI_MAX_VQ, vq + 1))
-		< VHOST_SCSI_MAX_VQ)
-		vhost_signal(&vs->dev, &vs->vqs[vq].vq);
+	if (signal)
+		vhost_signal(&svq->vs->dev, &svq->vq);
 }
 
 static struct vhost_scsi_cmd *
@@ -1776,6 +1772,7 @@ static int vhost_scsi_set_features(struct vhost_scsi *vs,
u64 features)
 
 static int vhost_scsi_open(struct inode *inode, struct file *f)
 {
+	struct vhost_scsi_virtqueue *svq;
 	struct vhost_scsi *vs;
 	struct vhost_virtqueue **vqs;
 	int r = -ENOMEM, i;
@@ -1788,7 +1785,6 @@ static int vhost_scsi_open(struct inode *inode, struct
file *f)
 	if (!vqs)
 		goto err_vqs;
 
-	vhost_work_init(&vs->vs_completion_work, vhost_scsi_complete_cmd_work);
 	vhost_work_init(&vs->vs_event_work, vhost_scsi_evt_work);
 
 	vs->vs_events_nr = 0;
@@ -1799,8 +1795,14 @@ static int vhost_scsi_open(struct inode *inode, struct
file *f)
 	vs->vqs[VHOST_SCSI_VQ_CTL].vq.handle_kick = vhost_scsi_ctl_handle_kick;
 	vs->vqs[VHOST_SCSI_VQ_EVT].vq.handle_kick = vhost_scsi_evt_handle_kick;
 	for (i = VHOST_SCSI_VQ_IO; i < VHOST_SCSI_MAX_VQ; i++) {
-		vqs[i] = &vs->vqs[i].vq;
-		vs->vqs[i].vq.handle_kick = vhost_scsi_handle_kick;
+		svq = &vs->vqs[i];
+
+		vqs[i] = &svq->vq;
+		svq->vs = vs;
+		init_llist_head(&svq->completion_list);
+		vhost_work_init(&svq->completion_work,
+				vhost_scsi_complete_cmd_work);
+		svq->vq.handle_kick = vhost_scsi_handle_kick;
 	}
 	vhost_dev_init(&vs->dev, vqs, VHOST_SCSI_MAX_VQ, UIO_MAXIOV,
 		       VHOST_SCSI_WEIGHT, 0, true, NULL);
-- 
2.25.1

Mike Christie

2021-Nov-04 19:04 UTC

head link

[PATCH V4 08/12] vhost-scsi: convert to vq helpers

Convert from vhost dev based helpers to vq ones.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/scsi.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 0d85ddb68420..08beba73ada4 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -361,8 +361,9 @@ static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)
 	if (se_cmd->se_cmd_flags & SCF_SCSI_TMR_CDB) {
 		struct vhost_scsi_tmf *tmf = container_of(se_cmd,
 					struct vhost_scsi_tmf, se_cmd);
+		struct vhost_virtqueue *vq = &tmf->svq->vq;
 
-		vhost_work_queue(&tmf->vhost->dev, &tmf->vwork);
+		vhost_vq_work_queue(vq, &tmf->vwork);
 	} else {
 		struct vhost_scsi_cmd *cmd = container_of(se_cmd,
 					struct vhost_scsi_cmd, tvc_se_cmd);
@@ -1360,11 +1361,9 @@ static void vhost_scsi_ctl_handle_kick(struct vhost_work
*work)
 }
 
 static void
-vhost_scsi_send_evt(struct vhost_scsi *vs,
-		   struct vhost_scsi_tpg *tpg,
-		   struct se_lun *lun,
-		   u32 event,
-		   u32 reason)
+vhost_scsi_send_evt(struct vhost_scsi *vs, struct vhost_virtqueue *vq,
+		    struct vhost_scsi_tpg *tpg, struct se_lun *lun,
+		    u32 event, u32 reason)
 {
 	struct vhost_scsi_evt *evt;
 
@@ -1386,7 +1385,7 @@ vhost_scsi_send_evt(struct vhost_scsi *vs,
 	}
 
 	llist_add(&evt->list, &vs->vs_event_list);
-	vhost_work_queue(&vs->dev, &vs->vs_event_work);
+	vhost_vq_work_queue(vq, &vs->vs_event_work);
 }
 
 static void vhost_scsi_evt_handle_kick(struct vhost_work *work)
@@ -1400,7 +1399,8 @@ static void vhost_scsi_evt_handle_kick(struct vhost_work
*work)
 		goto out;
 
 	if (vs->vs_events_missed)
-		vhost_scsi_send_evt(vs, NULL, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);
+		vhost_scsi_send_evt(vs, vq, NULL, NULL, VIRTIO_SCSI_T_NO_EVENT,
+				    0);
 out:
 	mutex_unlock(&vq->mutex);
 }
@@ -1428,11 +1428,10 @@ static void vhost_scsi_flush(struct vhost_scsi *vs)
 	 * indicate the start of the flush operation so that it will reach 0
 	 * when all the reqs are finished.
 	 */
-	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
+	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
 		kref_put(&old_inflight[i]->kref, vhost_scsi_done_inflight);
-
-	/* Flush both the vhost poll and vhost work */
-	vhost_work_dev_flush(&vs->dev);
+		vhost_vq_work_flush(&vs->vqs[i].vq);
+	}
 
 	/* Wait for all reqs issued before the flush to be finished */
 	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
@@ -1967,8 +1966,8 @@ vhost_scsi_do_plug(struct vhost_scsi_tpg *tpg,
 	vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
 	mutex_lock(&vq->mutex);
 	if (vhost_has_feature(vq, VIRTIO_SCSI_F_HOTPLUG))
-		vhost_scsi_send_evt(vs, tpg, lun,
-				   VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
+		vhost_scsi_send_evt(vs, vq, tpg, lun,
+				    VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
 	mutex_unlock(&vq->mutex);
 	mutex_unlock(&vs->dev.mutex);
 }
-- 
2.25.1

Mike Christie

2021-Nov-04 19:04 UTC

head link

[PATCH V4 09/12] vhost-scsi: flush IO vqs then send TMF rsp

With one worker we will always send the scsi cmd responses then send the
TMF rsp, because LIO will always complete the scsi cmds first then call
into us to send the TMF response.

With multiple workers, one of the IO vq threads could be run after the
TMF is queued, so this has us flush the IO vqs that don't share a woker
with the CTL vq (the vq that handles TMFs) before sending the TMF
response.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/scsi.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 08beba73ada4..29d9adcdb4fc 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1153,12 +1153,28 @@ static void vhost_scsi_tmf_resp_work(struct vhost_work
*work)
 {
 	struct vhost_scsi_tmf *tmf = container_of(work, struct vhost_scsi_tmf,
 						  vwork);
-	int resp_code;
+	struct vhost_virtqueue *ctl_vq, *vq;
+	int resp_code, i;
+
+	if (tmf->scsi_resp == TMR_FUNCTION_COMPLETE) {
+		/*
+		 * Flush IO vqs that don't share a worker with the ctl to make
+		 * sure they have sent their responses before us.
+		 */
+		ctl_vq = &tmf->vhost->vqs[VHOST_SCSI_VQ_CTL].vq;
+		for (i = VHOST_SCSI_VQ_IO; i < tmf->vhost->dev.nvqs; i++) {
+			vq = &tmf->vhost->vqs[i].vq;
+
+			if (vhost_vq_is_setup(vq) &&
+			    vq->worker != ctl_vq->worker) {
+				vhost_vq_work_flush(vq);
+			}
+		}
 
-	if (tmf->scsi_resp == TMR_FUNCTION_COMPLETE)
 		resp_code = VIRTIO_SCSI_S_FUNCTION_SUCCEEDED;
-	else
+	} else {
 		resp_code = VIRTIO_SCSI_S_FUNCTION_REJECTED;
+	}
 
 	vhost_scsi_send_tmf_resp(tmf->vhost, &tmf->svq->vq,
tmf->in_iovs,
 				 tmf->vq_desc, &tmf->resp_iov, resp_code);
-- 
2.25.1

Mike Christie

2021-Nov-04 19:05 UTC

head link

[PATCH V4 10/12] vhost: remove device wide queu/flushing helpers

vhost_work_queue and vhost_work_dev_flush are no longer used, so drop
them.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/vhost.c | 12 ------------
 drivers/vhost/vhost.h |  2 --
 2 files changed, 14 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c84024afefff..04f43a6445e1 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -268,24 +268,12 @@ void vhost_vq_work_flush(struct vhost_virtqueue *vq)
 }
 EXPORT_SYMBOL_GPL(vhost_vq_work_flush);
 
-void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
-{
-	vhost_work_queue_on(dev->worker, work);
-}
-EXPORT_SYMBOL_GPL(vhost_work_queue);
-
 void vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work)
 {
 	vhost_work_queue_on(vq->worker, work);
 }
 EXPORT_SYMBOL_GPL(vhost_vq_work_queue);
 
-void vhost_work_dev_flush(struct vhost_dev *dev)
-{
-	vhost_work_flush_on(dev->worker);
-}
-EXPORT_SYMBOL_GPL(vhost_work_dev_flush);
-
 /* Flush any work that has been scheduled. When calling this, don't hold
any
  * locks that are also used by the callback. */
 void vhost_poll_flush(struct vhost_poll *poll)
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index d9650da2be2c..33c63b24187a 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -50,7 +50,6 @@ struct vhost_poll {
 };
 
 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn);
-void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
 
 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
 		     __poll_t mask, struct vhost_dev *dev,
@@ -59,7 +58,6 @@ int vhost_poll_start(struct vhost_poll *poll, struct file
*file);
 void vhost_poll_stop(struct vhost_poll *poll);
 void vhost_poll_flush(struct vhost_poll *poll);
 void vhost_poll_queue(struct vhost_poll *poll);
-void vhost_work_dev_flush(struct vhost_dev *dev);
 
 struct vhost_log {
 	u64 addr;
-- 
2.25.1

Mike Christie

2021-Nov-04 19:05 UTC

head link

[PATCH V4 11/12] vhost: allow userspace to create workers

This patch allows userspace to create workers and bind them to vqs. You
can have N workers per dev and also share N workers with M vqs.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---
 drivers/vhost/vhost.c            | 149 ++++++++++++++++++++++++++++---
 drivers/vhost/vhost.h            |   4 +-
 include/uapi/linux/vhost.h       |  22 +++++
 include/uapi/linux/vhost_types.h |  15 ++++
 4 files changed, 178 insertions(+), 12 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 04f43a6445e1..20bf67a846f1 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -493,7 +493,6 @@ void vhost_dev_init(struct vhost_dev *dev,
 	dev->umem = NULL;
 	dev->iotlb = NULL;
 	dev->mm = NULL;
-	dev->worker = NULL;
 	dev->iov_limit = iov_limit;
 	dev->weight = weight;
 	dev->byte_weight = byte_weight;
@@ -503,6 +502,7 @@ void vhost_dev_init(struct vhost_dev *dev,
 	INIT_LIST_HEAD(&dev->read_list);
 	INIT_LIST_HEAD(&dev->pending_list);
 	spin_lock_init(&dev->iotlb_lock);
+	idr_init(&dev->worker_idr);
 
 
 	for (i = 0; i < dev->nvqs; ++i) {
@@ -576,31 +576,59 @@ static void vhost_worker_stop(struct vhost_worker *worker)
 	wait_for_completion(worker->exit_done);
 }
 
-static void vhost_worker_free(struct vhost_dev *dev)
+static void vhost_worker_put(struct vhost_dev *dev, struct vhost_worker
*worker)
 {
-	struct vhost_worker *worker = dev->worker;
-
 	if (!worker)
 		return;
 
-	dev->worker = NULL;
+	if (!refcount_dec_and_test(&worker->refcount))
+		return;
+
 	WARN_ON(!llist_empty(&worker->work_list));
 	vhost_worker_stop(worker);
+	idr_remove(&dev->worker_idr, worker->id);
 	kfree(worker);
 }
 
+static void vhost_vq_detach_worker(struct vhost_virtqueue *vq)
+{
+	if (vq->worker)
+		vhost_worker_put(vq->dev, vq->worker);
+	vq->worker = NULL;
+}
+
+static int vhost_workers_idr_iter(int id, void *worker, void *dev)
+{
+	vhost_worker_put(dev, worker);
+	return 0;
+}
+
+static void vhost_workers_free(struct vhost_dev *dev)
+{
+	int i;
+
+	if (!dev->use_worker)
+		return;
+
+	for (i = 0; i < dev->nvqs; i++)
+		vhost_vq_detach_worker(dev->vqs[i]);
+
+	idr_for_each(&dev->worker_idr, vhost_workers_idr_iter, dev);
+}
+
 static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
 {
 	struct vhost_worker *worker;
 	struct task_struct *task;
+	int id;
 
 	worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
 	if (!worker)
 		return NULL;
 
-	dev->worker = worker;
 	worker->kcov_handle = kcov_common_handle();
 	init_llist_head(&worker->work_list);
+	refcount_set(&worker->refcount, 1);
 
 	/*
 	 * vhost used to use the kthread API which ignores all signals by
@@ -613,14 +641,88 @@ static struct vhost_worker *vhost_worker_create(struct
vhost_dev *dev)
 
 	worker->task = task;
 	kernel_worker_start(task, "vhost-%d", current->pid);
+
+	/* idr accesses are done under the vhost_dev mutex */
+	id = idr_alloc(&dev->worker_idr, worker, 0, INT_MAX, GFP_KERNEL);
+	if (id < 0)
+		goto stop_worker;
+	worker->id = id;
+
 	return worker;
 
+stop_worker:
+	vhost_worker_stop(worker);
 free_worker:
 	kfree(worker);
-	dev->worker = NULL;
 	return NULL;
 }
 
+/* Caller must have device mutex */
+static int vhost_vq_attach_worker(struct vhost_virtqueue *vq,
+				  struct vhost_vring_worker *info)
+{
+	struct vhost_dev *dev = vq->dev;
+	struct vhost_worker *worker;
+
+	if (!dev->use_worker)
+		return -EINVAL;
+
+	/* We don't support setting a worker on an active vq */
+	if (vq->private_data)
+		return -EBUSY;
+
+	worker = idr_find(&dev->worker_idr, info->worker_id);
+	if (!worker)
+		return -ENODEV;
+
+	refcount_inc(&worker->refcount);
+
+	vhost_vq_detach_worker(vq);
+	vq->worker = worker;
+	return 0;
+}
+
+/* Caller must have device mutex */
+static int vhost_new_worker(struct vhost_dev *dev,
+			    struct vhost_worker_state *info)
+{
+	struct vhost_worker *worker;
+
+	if (!dev->use_worker)
+		return -EINVAL;
+
+	worker = vhost_worker_create(dev);
+	if (!worker)
+		return -ENOMEM;
+
+	info->worker_id = worker->id;
+	return 0;
+}
+
+/* Caller must have device mutex */
+static int vhost_free_worker(struct vhost_dev *dev,
+			     struct vhost_worker_state *info)
+{
+	struct vhost_worker *worker;
+
+	if (!dev->use_worker)
+		return -EINVAL;
+
+	worker = idr_find(&dev->worker_idr, info->worker_id);
+	if (!worker)
+		return -ENODEV;
+
+	/*
+	 * We can free the worker if there are no attached vqs and we only
+	 * have the refcount from the initial creation.
+	 */
+	if (refcount_read(&worker->refcount) != 1)
+		return -EBUSY;
+
+	vhost_worker_put(dev, worker);
+	return 0;
+}
+
 /* Caller should have device mutex */
 long vhost_dev_set_owner(struct vhost_dev *dev)
 {
@@ -640,8 +742,10 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
 		if (!worker)
 			goto err_worker;
 
-		for (i = 0; i < dev->nvqs; i++)
+		for (i = 0; i < dev->nvqs; i++) {
+			refcount_inc(&worker->refcount);
 			dev->vqs[i]->worker = worker;
+		}
 	}
 
 	err = vhost_dev_alloc_iovecs(dev);
@@ -650,7 +754,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
 
 	return 0;
 err_iovecs:
-	vhost_worker_free(dev);
+	vhost_workers_free(dev);
 err_worker:
 	vhost_detach_mm(dev);
 err_mm:
@@ -742,7 +846,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
 	dev->iotlb = NULL;
 	vhost_clear_msg(dev);
 	wake_up_interruptible_poll(&dev->wait, EPOLLIN | EPOLLRDNORM);
-	vhost_worker_free(dev);
+	vhost_workers_free(dev);
 	vhost_detach_mm(dev);
 }
 EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
@@ -1612,6 +1716,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int
ioctl, void __user *arg
 	struct eventfd_ctx *ctx = NULL;
 	u32 __user *idxp = argp;
 	struct vhost_virtqueue *vq;
+	struct vhost_vring_worker w;
 	struct vhost_vring_state s;
 	struct vhost_vring_file f;
 	u32 idx;
@@ -1719,7 +1824,16 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int
ioctl, void __user *arg
 		if (copy_to_user(argp, &s, sizeof(s)))
 			r = -EFAULT;
 		break;
-	default:
+	case VHOST_ATTACH_VRING_WORKER:
+		if (copy_from_user(&w, argp, sizeof(w))) {
+			r = -EFAULT;
+			break;
+		}
+		r = vhost_vq_attach_worker(vq, &w);
+		if (!r && copy_to_user(argp, &w, sizeof(w)))
+			r = -EFAULT;
+		break;
+default:
 		r = -ENOIOCTLCMD;
 	}
 
@@ -1772,6 +1886,7 @@ EXPORT_SYMBOL_GPL(vhost_init_device_iotlb);
 /* Caller must have device mutex */
 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user
*argp)
 {
+	struct vhost_worker_state w;
 	struct eventfd_ctx *ctx;
 	u64 p;
 	long r;
@@ -1832,6 +1947,18 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int
ioctl, void __user *argp)
 		if (ctx)
 			eventfd_ctx_put(ctx);
 		break;
+	case VHOST_NEW_WORKER:
+		r = vhost_new_worker(d, &w);
+		if (!r && copy_to_user(argp, &w, sizeof(w)))
+			r = -EFAULT;
+		break;
+	case VHOST_FREE_WORKER:
+		if (copy_from_user(&w, argp, sizeof(w))) {
+			r = -EFAULT;
+			break;
+		}
+		r = vhost_free_worker(d, &w);
+		break;
 	default:
 		r = -ENOIOCTLCMD;
 		break;
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 33c63b24187a..b3786e3537f1 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -35,6 +35,8 @@ struct vhost_worker {
 	struct llist_head	work_list;
 	u64			kcov_handle;
 	unsigned long		flags;
+	refcount_t		refcount;
+	int			id;
 };
 
 /* Poll a file (eventfd or socket) */
@@ -160,7 +162,6 @@ struct vhost_dev {
 	struct vhost_virtqueue **vqs;
 	int nvqs;
 	struct eventfd_ctx *log_ctx;
-	struct vhost_worker *worker;
 	struct vhost_iotlb *umem;
 	struct vhost_iotlb *iotlb;
 	spinlock_t iotlb_lock;
@@ -170,6 +171,7 @@ struct vhost_dev {
 	int iov_limit;
 	int weight;
 	int byte_weight;
+	struct idr worker_idr;
 	bool use_worker;
 	int (*msg_handler)(struct vhost_dev *dev,
 			   struct vhost_iotlb_msg *msg);
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index c998860d7bbc..117ea92b3925 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -45,6 +45,23 @@
 #define VHOST_SET_LOG_BASE _IOW(VHOST_VIRTIO, 0x04, __u64)
 /* Specify an eventfd file descriptor to signal on log write. */
 #define VHOST_SET_LOG_FD _IOW(VHOST_VIRTIO, 0x07, int)
+/* By default, a device gets one vhost_worker that its virtqueues share. This
+ * command allows the owner of the device to create an additional vhost_worker
+ * for the device. It can later be bound to 1 or more of its virtqueues using
+ * the VHOST_ATTACH_VRING_WORKER command.
+ *
+ * This must be called after VHOST_SET_OWNER and the caller must be the owner
+ * of the device. The new thread will inherit caller's cgroups and
namespaces,
+ * and will share the caller's memory space. The new thread will also be
+ * counted against the caller's RLIMIT_NPROC value.
+ */
+#define VHOST_NEW_WORKER _IOW(VHOST_VIRTIO, 0x8, struct vhost_worker_state)
+/* Free a worker created with VHOST_NEW_WORKER if it's not attached to any
+ * virtqueue. If userspace is not able to call this for workers its created,
+ * the kernel will free all the device's workers when the device is closed
and
+ * the last reference to the device has been released.
+ */
+#define VHOST_FREE_WORKER _IOR(VHOST_VIRTIO, 0x9, struct vhost_worker_state)
 
 /* Ring setup. */
 /* Set number of descriptors in ring. This parameter can not
@@ -70,6 +87,11 @@
 #define VHOST_VRING_BIG_ENDIAN 1
 #define VHOST_SET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x13, struct
vhost_vring_state)
 #define VHOST_GET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x14, struct
vhost_vring_state)
+/* Attach a vhost_worker created with VHOST_NEW_WORKER to one of the
device's
+ * virtqueues. This must be done before the virtqueue is active.
+ */
+#define VHOST_ATTACH_VRING_WORKER _IOR(VHOST_VIRTIO, 0x15,		\
+				       struct vhost_vring_worker)
 
 /* The following ioctls use eventfd file descriptors to signal and poll
  * for events. */
diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index f7f6a3a28977..d38a023e494f 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -47,6 +47,21 @@ struct vhost_vring_addr {
 	__u64 log_guest_addr;
 };
 
+struct vhost_worker_state {
+	/*
+	 * For VHOST_NEW_WORKER the kernel will return the new vhost_worker id.
+	 * For VHOST_FREE_WORKER this must be set to the id of the vhost_worker
+	 * to free.
+	 */
+	int worker_id;
+};
+
+struct vhost_vring_worker {
+	unsigned int index;
+	/* The id of the vhost_worker returned from VHOST_NEW_WORKER */
+	int worker_id;
+};
+
 /* no alignment requirement */
 struct vhost_iotlb_msg {
 	__u64 iova;
-- 
2.25.1

Mike Christie

2021-Nov-04 19:05 UTC

head link

[PATCH V4 12/12] vhost: allow worker attachment after initial setup

This patch allows userspace to change the vq to worker mapping while it's
in use so tools can do this setup post device creation if needed.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
---

 drivers/vhost/vhost.c      | 102 +++++++++++++++++++++++++------------
 drivers/vhost/vhost.h      |   2 +-
 include/uapi/linux/vhost.h |   2 +-
 3 files changed, 71 insertions(+), 35 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 20bf67a846f1..f47710a77853 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -232,12 +232,9 @@ void vhost_poll_stop(struct vhost_poll *poll)
 }
 EXPORT_SYMBOL_GPL(vhost_poll_stop);
 
-static void vhost_work_queue_on(struct vhost_worker *worker,
-				struct vhost_work *work)
+static void vhost_worker_work_queue(struct vhost_worker *worker,
+				    struct vhost_work *work)
 {
-	if (!worker)
-		return;
-
 	if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
 		/* We can only add the work to the list after we're
 		 * sure it was not in the list.
@@ -248,31 +245,45 @@ static void vhost_work_queue_on(struct vhost_worker
*worker,
 	}
 }
 
-static void vhost_work_flush_on(struct vhost_worker *worker)
+void vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work)
 {
-	struct vhost_flush_struct flush;
+	struct vhost_worker *worker;
 
-	if (!worker)
-		return;
+	rcu_read_lock();
+	worker = rcu_dereference(vq->worker);
+	if (worker)
+		vhost_worker_work_queue(worker, work);
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(vhost_vq_work_queue);
 
-	init_completion(&flush.wait_event);
-	vhost_work_init(&flush.work, vhost_flush_work);
+static void vhost_worker_flush_queue(struct vhost_worker *worker,
+				     struct vhost_flush_struct *flush)
+{
+	init_completion(&flush->wait_event);
+	vhost_work_init(&flush->work, vhost_flush_work);
 
-	vhost_work_queue_on(worker, &flush.work);
-	wait_for_completion(&flush.wait_event);
+	vhost_worker_work_queue(worker, &flush->work);
 }
 
 void vhost_vq_work_flush(struct vhost_virtqueue *vq)
 {
-	vhost_work_flush_on(vq->worker);
-}
-EXPORT_SYMBOL_GPL(vhost_vq_work_flush);
+	struct vhost_flush_struct flush;
+	struct vhost_worker *worker;
 
-void vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work)
-{
-	vhost_work_queue_on(vq->worker, work);
+	rcu_read_lock();
+	worker = rcu_dereference(vq->worker);
+	if (!worker) {
+		rcu_read_unlock();
+		return;
+	}
+
+	vhost_worker_flush_queue(worker, &flush);
+	rcu_read_unlock();
+
+	wait_for_completion(&flush.wait_event);
 }
-EXPORT_SYMBOL_GPL(vhost_vq_work_queue);
+EXPORT_SYMBOL_GPL(vhost_vq_work_flush);
 
 /* Flush any work that has been scheduled. When calling this, don't hold
any
  * locks that are also used by the callback. */
@@ -285,7 +296,16 @@ EXPORT_SYMBOL_GPL(vhost_poll_flush);
 /* A lockless hint for busy polling code to exit the loop */
 bool vhost_vq_has_work(struct vhost_virtqueue *vq)
 {
-	return vq->worker &&
!llist_empty(&vq->worker->work_list);
+	struct vhost_worker *worker;
+	bool has_work = false;
+
+	rcu_read_lock();
+	worker = rcu_dereference(vq->worker);
+	if (worker && !llist_empty(&worker->work_list))
+		has_work = true;
+	rcu_read_unlock();
+
+	return has_work;
 }
 EXPORT_SYMBOL_GPL(vhost_vq_has_work);
 
@@ -510,7 +530,7 @@ void vhost_dev_init(struct vhost_dev *dev,
 		vq->log = NULL;
 		vq->indirect = NULL;
 		vq->heads = NULL;
-		vq->worker = NULL;
+		rcu_assign_pointer(vq->worker, NULL);
 		vq->dev = dev;
 		mutex_init(&vq->mutex);
 		vhost_vq_reset(dev, vq);
@@ -590,11 +610,32 @@ static void vhost_worker_put(struct vhost_dev *dev, struct
vhost_worker *worker)
 	kfree(worker);
 }
 
-static void vhost_vq_detach_worker(struct vhost_virtqueue *vq)
+static void vhost_vq_swap_worker(struct vhost_virtqueue *vq,
+				 struct vhost_worker *new_worker, bool flush)
 {
-	if (vq->worker)
-		vhost_worker_put(vq->dev, vq->worker);
-	vq->worker = NULL;
+	struct vhost_flush_struct flush_work;
+	struct vhost_worker *old_worker;
+
+	old_worker = rcu_dereference_check(vq->worker,
+					   lockdep_is_held(&vq->dev->mutex));
+	rcu_assign_pointer(vq->worker, new_worker);
+
+	if (!old_worker)
+		return;
+
+	if (flush) {
+		/*
+		 * For dev cleanup we won't have work running, but for the
+		 * dynamic attach case we might so make sure we see the new
+		 * worker and there is no work in the old worker.
+		 */
+		synchronize_rcu();
+
+		vhost_worker_flush_queue(old_worker, &flush_work);
+		wait_for_completion(&flush_work.wait_event);
+	}
+
+	vhost_worker_put(vq->dev, old_worker);
 }
 
 static int vhost_workers_idr_iter(int id, void *worker, void *dev)
@@ -611,7 +652,7 @@ static void vhost_workers_free(struct vhost_dev *dev)
 		return;
 
 	for (i = 0; i < dev->nvqs; i++)
-		vhost_vq_detach_worker(dev->vqs[i]);
+		vhost_vq_swap_worker(dev->vqs[i], NULL, false);
 
 	idr_for_each(&dev->worker_idr, vhost_workers_idr_iter, dev);
 }
@@ -667,18 +708,13 @@ static int vhost_vq_attach_worker(struct vhost_virtqueue
*vq,
 	if (!dev->use_worker)
 		return -EINVAL;
 
-	/* We don't support setting a worker on an active vq */
-	if (vq->private_data)
-		return -EBUSY;
-
 	worker = idr_find(&dev->worker_idr, info->worker_id);
 	if (!worker)
 		return -ENODEV;
 
 	refcount_inc(&worker->refcount);
 
-	vhost_vq_detach_worker(vq);
-	vq->worker = worker;
+	vhost_vq_swap_worker(vq, worker, true);
 	return 0;
 }
 
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index b3786e3537f1..607e95887942 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -81,7 +81,7 @@ struct vhost_vring_call {
 /* The virtqueue structure describes a queue attached to a device. */
 struct vhost_virtqueue {
 	struct vhost_dev *dev;
-	struct vhost_worker *worker;
+	struct vhost_worker __rcu *worker;
 
 	/* The actual ring of buffers. */
 	struct mutex mutex;
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index 117ea92b3925..e0221c8ce877 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -88,7 +88,7 @@
 #define VHOST_SET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x13, struct
vhost_vring_state)
 #define VHOST_GET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x14, struct
vhost_vring_state)
 /* Attach a vhost_worker created with VHOST_NEW_WORKER to one of the
device's
- * virtqueues. This must be done before the virtqueue is active.
+ * virtqueues.
  */
 #define VHOST_ATTACH_VRING_WORKER _IOR(VHOST_VIRTIO, 0x15,		\
 				       struct vhost_vring_worker)
-- 
2.25.1

Virtualization - Nov 2021 - [PATCH V4 02/12] vhost, vhost-net: add helper to check if vq has work

[PATCH V4 00/12] vhost: multiple worker support

[PATCH V4 01/12] vhost: add vhost_worker pointer to vhost_virtqueue

[PATCH V4 02/12] vhost, vhost-net: add helper to check if vq has work

[PATCH V4 03/12] vhost: take worker or vq instead of dev for queueing

[PATCH V4 04/12] vhost: take worker or vq instead of dev for flushing

[PATCH V4 05/12] vhost: convert poll work to be vq based

[PATCH V4 06/12] vhost-sock: convert to vq helpers

[PATCH V4 07/12] vhost-scsi: make SCSI cmd completion per vq

[PATCH V4 08/12] vhost-scsi: convert to vq helpers

[PATCH V4 09/12] vhost-scsi: flush IO vqs then send TMF rsp

[PATCH V4 10/12] vhost: remove device wide queu/flushing helpers

[PATCH V4 11/12] vhost: allow userspace to create workers

[PATCH V4 12/12] vhost: allow worker attachment after initial setup