Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 5e59d9a1 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Michael S. Tsirkin
Browse files

virtio_console: Stop doing DMA on the stack 



virtio_console uses a small DMA buffer for control requests.  Move
that buffer into heap memory.

Doing virtio DMA on the stack is normally okay on non-DMA-API virtio
systems (which is currently most of them), but it breaks completely
if the stack is virtually mapped.

Tested by typing both directions using picocom aimed at /dev/hvc0.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: default avatarAmit Shah <amit.shah@redhat.com>
parent af7c1bec

drivers/char/virtio_console.c

+15 −8
Original line number Diff line number Diff line
@@ -165,6 +165,12 @@ struct ports_device { 
	 */

	struct virtqueue *c_ivq, *c_ovq;



	/*

	 * A control packet buffer for guest->host requests, protected

	 * by c_ovq_lock.

	 */

	struct virtio_console_control cpkt;



	/* Array of per-port IO virtqueues */

	struct virtqueue **in_vqs, **out_vqs;
@@ -560,28 +566,29 @@ static ssize_t __send_control_msg(struct ports_device *portdev, u32 port_id, 
				  unsigned int event, unsigned int value)

{

	struct scatterlist sg[1];

	struct virtio_console_control cpkt;

	struct virtqueue *vq;

	unsigned int len;



	if (!use_multiport(portdev))

		return 0;



	cpkt.id = cpu_to_virtio32(portdev->vdev, port_id);

	cpkt.event = cpu_to_virtio16(portdev->vdev, event);

	cpkt.value = cpu_to_virtio16(portdev->vdev, value);



	vq = portdev->c_ovq;



	sg_init_one(sg, &cpkt, sizeof(cpkt));



	spin_lock(&portdev->c_ovq_lock);

	if (virtqueue_add_outbuf(vq, sg, 1, &cpkt, GFP_ATOMIC) == 0) {



	portdev->cpkt.id = cpu_to_virtio32(portdev->vdev, port_id);

	portdev->cpkt.event = cpu_to_virtio16(portdev->vdev, event);

	portdev->cpkt.value = cpu_to_virtio16(portdev->vdev, value);



	sg_init_one(sg, &portdev->cpkt, sizeof(struct virtio_console_control));



	if (virtqueue_add_outbuf(vq, sg, 1, &portdev->cpkt, GFP_ATOMIC) == 0) {

		virtqueue_kick(vq);

		while (!virtqueue_get_buf(vq, &len)

			&& !virtqueue_is_broken(vq))

			cpu_relax();

	}



	spin_unlock(&portdev->c_ovq_lock);

	return 0;

}