For non-linear skb use its pages from fragment array as buffers in
virtio tx queue. These pages are already pinned by 'get_user_pages()'
during such skb creation.
Signed-off-by: Arseniy Krasnov <avkrasnov@xxxxxxxxxxxxxxxxx>
---
Changelog:
v2 -> v3:
* Comment about 'page_to_virt()' is updated. I don't remove R-b,
as this change is quiet small I guess.
v6 -> v7:
* Move arrays '*sgs' and 'bufs' to 'virtio_vsock' instead of being
local variables. This allows to save stack space in cases of too
big MAX_SKB_FRAGS.
* Add 'WARN_ON_ONCE()' for handling nonlinear skbs - it checks that
linear part of such skb contains only header.
* R-b tag removed due to updates above.
v7 -> v8:
* Add comment in 'struct virtio_vsock' for both 'struct scatterlist'
fields.
* Rename '*sgs' and 'bufs' to '*out_sgs' and 'out_bufs'.
* Initialize '*out_sgs' in 'virtio_vsock_probe()' by always pointing
to the corresponding element of 'out_bufs'.
net/vmw_vsock/virtio_transport.c | 60 ++++++++++++++++++++++++++++----
1 file changed, 53 insertions(+), 7 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index e95df847176b..73d730156349 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -63,6 +63,17 @@ struct virtio_vsock {
u32 guest_cid;
bool seqpacket_allow;
+
+ /* These fields are used only in tx path in function
+ * 'virtio_transport_send_pkt_work()', so to save
+ * stack space in it, place both of them here. Each
+ * pointer from 'out_sgs' points to the corresponding
+ * element in 'out_bufs' - this is initialized in
+ * 'virtio_vsock_probe()'. Both fields are protected
+ * by 'tx_lock'. +1 is needed for packet header.
+ */
+ struct scatterlist *out_sgs[MAX_SKB_FRAGS + 1];
+ struct scatterlist out_bufs[MAX_SKB_FRAGS + 1];
};
static u32 virtio_transport_get_local_cid(void)
@@ -100,8 +111,8 @@ virtio_transport_send_pkt_work(struct work_struct *work)
vq = vsock->vqs[VSOCK_VQ_TX];
for (;;) {
- struct scatterlist hdr, buf, *sgs[2];
int ret, in_sg = 0, out_sg = 0;
+ struct scatterlist **sgs;
struct sk_buff *skb;
bool reply;
@@ -111,12 +122,43 @@ virtio_transport_send_pkt_work(struct work_struct *work)
virtio_transport_deliver_tap_pkt(skb);
reply = virtio_vsock_skb_reply(skb);
-
- sg_init_one(&hdr, virtio_vsock_hdr(skb), sizeof(*virtio_vsock_hdr(skb)));
- sgs[out_sg++] = &hdr;
- if (skb->len > 0) {
- sg_init_one(&buf, skb->data, skb->len);
- sgs[out_sg++] = &buf;
+ sgs = vsock->out_sgs;
+ sg_init_one(sgs[out_sg], virtio_vsock_hdr(skb),
+ sizeof(*virtio_vsock_hdr(skb)));
+ out_sg++;
+
+ if (!skb_is_nonlinear(skb)) {
+ if (skb->len > 0) {
+ sg_init_one(sgs[out_sg], skb->data, skb->len);
+ out_sg++;
+ }
+ } else {
+ struct skb_shared_info *si;
+ int i;
+
+ /* If skb is nonlinear, then its buffer must contain
+ * only header and nothing more. Data is stored in
+ * the fragged part.
+ */
+ WARN_ON_ONCE(skb_headroom(skb) != sizeof(*virtio_vsock_hdr(skb)));
+
+ si = skb_shinfo(skb);
+
+ for (i = 0; i < si->nr_frags; i++) {
+ skb_frag_t *skb_frag = &si->frags[i];
+ void *va;
+
+ /* We will use 'page_to_virt()' for the userspace page
+ * here, because virtio or dma-mapping layers will call
+ * 'virt_to_phys()' later to fill the buffer descriptor.
+ * We don't touch memory at "virtual" address of this page.
+ */
+ va = page_to_virt(skb_frag->bv_page);
+ sg_init_one(sgs[out_sg],
+ va + skb_frag->bv_offset,
+ skb_frag->bv_len);
+ out_sg++;
+ }
}
ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
@@ -621,6 +663,7 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
{
struct virtio_vsock *vsock = NULL;
int ret;
+ int i;
ret = mutex_lock_interruptible(&the_virtio_vsock_mutex);
if (ret)
@@ -663,6 +706,9 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
if (ret < 0)
goto out;
+ for (i = 0; i < ARRAY_SIZE(vsock->out_sgs); i++)
+ vsock->out_sgs[i] = &vsock->out_bufs[i];
+
rcu_assign_pointer(the_virtio_vsock, vsock);
mutex_unlock(&the_virtio_vsock_mutex);
--
2.25.1
