linux-kernel - [PATCH] virtio-net: Remove more stack DMA

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Date:	Mon, 11 Jul 2016 14:30:28 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Andy Lutomirski <luto@...nel.org>,
	"Michael S . Tsirkin" <mst@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: [PATCH] virtio-net: Remove more stack DMA

VLAN and MQ control was doing DMA from the stack.  Fix it.

Cc: Michael S. Tsirkin <mst@...hat.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---

I tested VLAN addition and removal with CONFIG_VMAP_STACK=y,
CONFIG_DEBUG_SG=y and it got rid of the warnings I saw.  I haven't
tested the MQ part because I don't know how to enable it in the first
place (I'm guessing it needs me to enable some QEMU feature I don't
know about.)

Michael, can you double-check this? DaveM, is it okay for this to go
in via -tip?

 drivers/net/virtio_net.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e0638e556fe7..5044ca37d725 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -144,8 +144,10 @@ struct virtnet_info {
 	/* Control VQ buffers: protected by the rtnl lock */
 	struct virtio_net_ctrl_hdr ctrl_hdr;
 	virtio_net_ctrl_ack ctrl_status;
+	struct virtio_net_ctrl_mq ctrl_mq;
 	u8 ctrl_promisc;
 	u8 ctrl_allmulti;
+	u16 ctrl_vid;
 
 	/* Ethtool settings */
 	u8 duplex;
@@ -1116,14 +1118,13 @@ static void virtnet_ack_link_announce(struct virtnet_info *vi)
 static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
 {
 	struct scatterlist sg;
-	struct virtio_net_ctrl_mq s;
 	struct net_device *dev = vi->dev;
 
 	if (!vi->has_cvq || !virtio_has_feature(vi->vdev, VIRTIO_NET_F_MQ))
 		return 0;
 
-	s.virtqueue_pairs = cpu_to_virtio16(vi->vdev, queue_pairs);
-	sg_init_one(&sg, &s, sizeof(s));
+	vi->ctrl_mq.virtqueue_pairs = cpu_to_virtio16(vi->vdev, queue_pairs);
+	sg_init_one(&sg, &vi->ctrl_mq, sizeof(vi->ctrl_mq));
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MQ,
 				  VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET, &sg)) {
@@ -1230,7 +1231,8 @@ static int virtnet_vlan_rx_add_vid(struct net_device *dev,
 	struct virtnet_info *vi = netdev_priv(dev);
 	struct scatterlist sg;
 
-	sg_init_one(&sg, &vid, sizeof(vid));
+	vi->ctrl_vid = vid;
+	sg_init_one(&sg, &vi->ctrl_vid, sizeof(vi->ctrl_vid));
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_VLAN,
 				  VIRTIO_NET_CTRL_VLAN_ADD, &sg))
@@ -1244,7 +1246,8 @@ static int virtnet_vlan_rx_kill_vid(struct net_device *dev,
 	struct virtnet_info *vi = netdev_priv(dev);
 	struct scatterlist sg;
 
-	sg_init_one(&sg, &vid, sizeof(vid));
+	vi->ctrl_vid = vid;
+	sg_init_one(&sg, &vi->ctrl_vid, sizeof(vi->ctrl_vid));
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_VLAN,
 				  VIRTIO_NET_CTRL_VLAN_DEL, &sg))
-- 
2.7.4