Commit-ID: 9472fe7040bba45c6200858cbe40d643cf02bccb
Gitweb: http://git.kernel.org/tip/9472fe7040bba45c6200858cbe40d643cf02bccb
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Tue, 30 Aug 2016 08:04:15 -0700
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 8 Sep 2016 08:48:35 +0200
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 (CONFIG_VMAP_STACK=y).
Tested by typing both directions using picocom aimed at /dev/hvc0.
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Reviewed-by: Amit Shah <amit.shah@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/0afe68f9b4be6c95af9e7672b07acd0274c26dfe.1472569320.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
drivers/char/virtio_console.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index d2406fe..5da47e26 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -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;
}
--
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