[PATCH 3.16 224/366] virtio_console: free buffers after reset

Ben Hutchings
2018-10-14T23:11:45Z

From: "Michael S. Tsirkin" <mst@redhat.com>

commit a7a69ec0d8e4a58be7db88d33cbfa2912807bb2b upstream.

Console driver is out of spec. The spec says:
A driver MUST NOT decrement the available idx on a live
virtqueue (ie. there is no way to “unexpose” buffers).
and it does exactly that by trying to detach unused buffers
without doing a device reset first.

Defer detaching the buffers until device unplug.

Of course this means we might get an interrupt for
a vq without an attached port now. Handle that by
discarding the consumed buffer.

Reported-by: Tiwei Bie <tiwei.bie@intel.com>
Fixes: b3258ff1d6 ("virtio: Decrement avail idx on buffer detach")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/char/virtio_console.c | 49 +++++++++++++++++------------------
1 file changed, 24 insertions(+), 25 deletions(-)

--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1398,7 +1398,6 @@ static int add_port(struct ports_device
{
char debugfs_name[16];
struct port *port;
- struct port_buffer *buf;
dev_t devt;
unsigned int nr_added_bufs;
int err;
@@ -1509,8 +1508,6 @@ static int add_port(struct ports_device
return 0;

free_inbufs:
- while ((buf = virtqueue_detach_unused_buf(port->in_vq)))
- free_buf(buf, true);
free_device:
device_destroy(pdrvdata.class, port->dev->devt);
free_cdev:
@@ -1535,34 +1532,14 @@ static void remove_port(struct kref *kre

static void remove_port_data(struct port *port)
{
- struct port_buffer *buf;
-
spin_lock_irq(&port->inbuf_lock);
/* Remove unused data this port might have received. */
discard_port_data(port);
spin_unlock_irq(&port->inbuf_lock);

- /* Remove buffers we queued up for the Host to send us data in. */
- do {
- spin_lock_irq(&port->inbuf_lock);
- buf = virtqueue_detach_unused_buf(port->in_vq);
- spin_unlock_irq(&port->inbuf_lock);
- if (buf)
- free_buf(buf, true);
- } while (buf);
-
spin_lock_irq(&port->outvq_lock);
reclaim_consumed_buffers(port);
spin_unlock_irq(&port->outvq_lock);
-
- /* Free pending buffers from the out-queue. */
- do {
- spin_lock_irq(&port->outvq_lock);
- buf = virtqueue_detach_unused_buf(port->out_vq);
- spin_unlock_irq(&port->outvq_lock);
- if (buf)
- free_buf(buf, true);
- } while (buf);
}

/*
@@ -1783,13 +1760,24 @@ static void control_work_handler(struct
spin_unlock(&portdev->c_ivq_lock);
}

+static void flush_bufs(struct virtqueue *vq, bool can_sleep)
+{
+ struct port_buffer *buf;
+ unsigned int len;
+
+ while ((buf = virtqueue_get_buf(vq, &len)))
+ free_buf(buf, can_sleep);
+}
+
static void out_intr(struct virtqueue *vq)
{
struct port *port;

port = find_port_by_vq(vq->vdev->priv, vq);
- if (!port)
+ if (!port) {
+ flush_bufs(vq, false);
return;
+ }

wake_up_interruptible(&port->waitqueue);
}
@@ -1800,8 +1788,10 @@ static void in_intr(struct virtqueue *vq
unsigned long flags;

port = find_port_by_vq(vq->vdev->priv, vq);
- if (!port)
+ if (!port) {
+ flush_bufs(vq, false);
return;
+ }

spin_lock_irqsave(&port->inbuf_lock, flags);
port->inbuf = get_inbuf(port);
@@ -1976,6 +1966,15 @@ static const struct file_operations port

static void remove_vqs(struct ports_device *portdev)
{
+ struct virtqueue *vq;
+
+ virtio_device_for_each_vq(portdev->vdev, vq) {
+ struct port_buffer *buf;
+
+ flush_bufs(vq, true);
+ while ((buf = virtqueue_detach_unused_buf(vq)))
+ free_buf(buf, true);
+ }
portdev->vdev->config->del_vqs(portdev->vdev);
kfree(portdev->in_vqs);
kfree(portdev->out_vqs);