* [PATCH net-next v6 1/4] vsock/virtio/vhost: read data from non-linear skb
2023-08-14 21:27 [PATCH net-next v6 0/4] vsock/virtio/vhost: MSG_ZEROCOPY preparations Arseniy Krasnov
@ 2023-08-14 21:27 ` Arseniy Krasnov
2023-08-14 21:27 ` [PATCH net-next v6 2/4] vsock/virtio: support to send " Arseniy Krasnov
` (2 subsequent siblings)
3 siblings, 0 replies; 7+ messages in thread
From: Arseniy Krasnov @ 2023-08-14 21:27 UTC (permalink / raw)
To: Stefan Hajnoczi, Stefano Garzarella, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Michael S. Tsirkin,
Jason Wang, Bobby Eshleman
Cc: kvm, virtualization, netdev, linux-kernel, kernel, oxffffaa,
avkrasnov, Arseniy Krasnov
This is preparation patch for MSG_ZEROCOPY support. It adds handling of
non-linear skbs by replacing direct calls of 'memcpy_to_msg()' with
'skb_copy_datagram_iter()'. Main advantage of the second one is that it
can handle paged part of the skb by using 'kmap()' on each page, but if
there are no pages in the skb, it behaves like simple copying to iov
iterator. This patch also adds new field to the control block of skb -
this value shows current offset in the skb to read next portion of data
(it doesn't matter linear it or not). Idea behind this field is that
'skb_copy_datagram_iter()' handles both types of skb internally - it
just needs an offset from which to copy data from the given skb. This
offset is incremented on each read from skb. This approach allows to
simplify handling of both linear and non-linear skbs, because for
linear skb we need to call 'skb_pull()' after reading data from it,
while in non-linear case we need to update 'data_len'.
Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
Changelog:
v5(big patchset) -> v1:
* Merge 'virtio_transport_common.c' and 'vhost/vsock.c' patches into
this single patch.
* Commit message update: grammar fix and remark that this patch is
MSG_ZEROCOPY preparation.
* Use 'min_t()' instead of comparison using '<>' operators.
v1 -> v2:
* R-b tag added.
v3 -> v4:
* R-b tag removed due to rebase:
* Part for 'virtio_transport_stream_do_peek()' is changed.
* Part for 'virtio_transport_seqpacket_do_peek()' is added.
* Comments about sleep in 'memcpy_to_msg()' now describe sleep in
'skb_copy_datagram_iter()'.
v5 -> v6:
* Commit message update.
* Rename 'frag_off' to 'offset' in 'virtio_vsock_skb_cb'.
drivers/vhost/vsock.c | 14 +++++++----
include/linux/virtio_vsock.h | 1 +
net/vmw_vsock/virtio_transport_common.c | 32 +++++++++++++++----------
3 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 817d377a3f36..83711aad855c 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -114,6 +114,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
struct sk_buff *skb;
unsigned out, in;
size_t nbytes;
+ u32 offset;
int head;
skb = virtio_vsock_skb_dequeue(&vsock->send_pkt_queue);
@@ -156,7 +157,8 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
}
iov_iter_init(&iov_iter, ITER_DEST, &vq->iov[out], in, iov_len);
- payload_len = skb->len;
+ offset = VIRTIO_VSOCK_SKB_CB(skb)->offset;
+ payload_len = skb->len - offset;
hdr = virtio_vsock_hdr(skb);
/* If the packet is greater than the space available in the
@@ -197,8 +199,10 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
break;
}
- nbytes = copy_to_iter(skb->data, payload_len, &iov_iter);
- if (nbytes != payload_len) {
+ if (skb_copy_datagram_iter(skb,
+ offset,
+ &iov_iter,
+ payload_len)) {
kfree_skb(skb);
vq_err(vq, "Faulted on copying pkt buf\n");
break;
@@ -212,13 +216,13 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
vhost_add_used(vq, head, sizeof(*hdr) + payload_len);
added = true;
- skb_pull(skb, payload_len);
+ VIRTIO_VSOCK_SKB_CB(skb)->offset += payload_len;
total_len += payload_len;
/* If we didn't send all the payload we can requeue the packet
* to send it with the next available buffer.
*/
- if (skb->len > 0) {
+ if (VIRTIO_VSOCK_SKB_CB(skb)->offset < skb->len) {
hdr->flags |= cpu_to_le32(flags_to_restore);
/* We are queueing the same skb to handle
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index c58453699ee9..a91fbdf233e4 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -12,6 +12,7 @@
struct virtio_vsock_skb_cb {
bool reply;
bool tap_delivered;
+ u32 offset;
};
#define VIRTIO_VSOCK_SKB_CB(skb) ((struct virtio_vsock_skb_cb *)((skb)->cb))
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 352d042b130b..3e08d52a9355 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -364,9 +364,10 @@ virtio_transport_stream_do_peek(struct vsock_sock *vsk,
spin_unlock_bh(&vvs->rx_lock);
/* sk_lock is held by caller so no one else can dequeue.
- * Unlock rx_lock since memcpy_to_msg() may sleep.
+ * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
*/
- err = memcpy_to_msg(msg, skb->data, bytes);
+ err = skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->offset,
+ &msg->msg_iter, bytes);
if (err)
goto out;
@@ -410,25 +411,27 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
while (total < len && !skb_queue_empty(&vvs->rx_queue)) {
skb = skb_peek(&vvs->rx_queue);
- bytes = len - total;
- if (bytes > skb->len)
- bytes = skb->len;
+ bytes = min_t(size_t, len - total,
+ skb->len - VIRTIO_VSOCK_SKB_CB(skb)->offset);
/* sk_lock is held by caller so no one else can dequeue.
- * Unlock rx_lock since memcpy_to_msg() may sleep.
+ * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
*/
spin_unlock_bh(&vvs->rx_lock);
- err = memcpy_to_msg(msg, skb->data, bytes);
+ err = skb_copy_datagram_iter(skb,
+ VIRTIO_VSOCK_SKB_CB(skb)->offset,
+ &msg->msg_iter, bytes);
if (err)
goto out;
spin_lock_bh(&vvs->rx_lock);
total += bytes;
- skb_pull(skb, bytes);
- if (skb->len == 0) {
+ VIRTIO_VSOCK_SKB_CB(skb)->offset += bytes;
+
+ if (skb->len == VIRTIO_VSOCK_SKB_CB(skb)->offset) {
u32 pkt_len = le32_to_cpu(virtio_vsock_hdr(skb)->len);
virtio_transport_dec_rx_pkt(vvs, pkt_len);
@@ -492,9 +495,10 @@ virtio_transport_seqpacket_do_peek(struct vsock_sock *vsk,
spin_unlock_bh(&vvs->rx_lock);
/* sk_lock is held by caller so no one else can dequeue.
- * Unlock rx_lock since memcpy_to_msg() may sleep.
+ * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
*/
- err = memcpy_to_msg(msg, skb->data, bytes);
+ err = skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->offset,
+ &msg->msg_iter, bytes);
if (err)
return err;
@@ -553,11 +557,13 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
int err;
/* sk_lock is held by caller so no one else can dequeue.
- * Unlock rx_lock since memcpy_to_msg() may sleep.
+ * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
*/
spin_unlock_bh(&vvs->rx_lock);
- err = memcpy_to_msg(msg, skb->data, bytes_to_copy);
+ err = skb_copy_datagram_iter(skb, 0,
+ &msg->msg_iter,
+ bytes_to_copy);
if (err) {
/* Copy of message failed. Rest of
* fragments will be freed without copy.
--
2.25.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH net-next v6 2/4] vsock/virtio: support to send non-linear skb
2023-08-14 21:27 [PATCH net-next v6 0/4] vsock/virtio/vhost: MSG_ZEROCOPY preparations Arseniy Krasnov
2023-08-14 21:27 ` [PATCH net-next v6 1/4] vsock/virtio/vhost: read data from non-linear skb Arseniy Krasnov
@ 2023-08-14 21:27 ` Arseniy Krasnov
2023-08-22 8:16 ` Paolo Abeni
2023-08-14 21:27 ` [PATCH net-next v6 3/4] vsock/virtio: non-linear skb handling for tap Arseniy Krasnov
2023-08-14 21:27 ` [PATCH net-next v6 4/4] vsock/virtio: MSG_ZEROCOPY flag support Arseniy Krasnov
3 siblings, 1 reply; 7+ messages in thread
From: Arseniy Krasnov @ 2023-08-14 21:27 UTC (permalink / raw)
To: Stefan Hajnoczi, Stefano Garzarella, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Michael S. Tsirkin,
Jason Wang, Bobby Eshleman
Cc: kvm, virtualization, netdev, linux-kernel, kernel, oxffffaa,
avkrasnov, Arseniy Krasnov
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@sberdevices.ru>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
---
Changelog:
v2 -> v3:
* Comment about 'page_to_virt()' is updated. I don't remove R-b,
as this change is quiet small I guess.
net/vmw_vsock/virtio_transport.c | 41 +++++++++++++++++++++++++++-----
1 file changed, 35 insertions(+), 6 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index e95df847176b..7bbcc8093e51 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -100,7 +100,9 @@ virtio_transport_send_pkt_work(struct work_struct *work)
vq = vsock->vqs[VSOCK_VQ_TX];
for (;;) {
- struct scatterlist hdr, buf, *sgs[2];
+ /* +1 is for packet header. */
+ struct scatterlist *sgs[MAX_SKB_FRAGS + 1];
+ struct scatterlist bufs[MAX_SKB_FRAGS + 1];
int ret, in_sg = 0, out_sg = 0;
struct sk_buff *skb;
bool reply;
@@ -111,12 +113,39 @@ virtio_transport_send_pkt_work(struct work_struct *work)
virtio_transport_deliver_tap_pkt(skb);
reply = virtio_vsock_skb_reply(skb);
+ sg_init_one(&bufs[out_sg], virtio_vsock_hdr(skb),
+ sizeof(*virtio_vsock_hdr(skb)));
+ sgs[out_sg] = &bufs[out_sg];
+ out_sg++;
+
+ if (!skb_is_nonlinear(skb)) {
+ if (skb->len > 0) {
+ sg_init_one(&bufs[out_sg], skb->data, skb->len);
+ sgs[out_sg] = &bufs[out_sg];
+ out_sg++;
+ }
+ } else {
+ struct skb_shared_info *si;
+ int i;
+
+ si = skb_shinfo(skb);
+
+ for (i = 0; i < si->nr_frags; i++) {
+ skb_frag_t *skb_frag = &si->frags[i];
+ void *va;
- 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;
+ /* 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(&bufs[out_sg],
+ va + skb_frag->bv_offset,
+ skb_frag->bv_len);
+ sgs[out_sg] = &bufs[out_sg];
+ out_sg++;
+ }
}
ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
--
2.25.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH net-next v6 2/4] vsock/virtio: support to send non-linear skb
2023-08-14 21:27 ` [PATCH net-next v6 2/4] vsock/virtio: support to send " Arseniy Krasnov
@ 2023-08-22 8:16 ` Paolo Abeni
2023-08-23 6:54 ` Arseniy Krasnov
0 siblings, 1 reply; 7+ messages in thread
From: Paolo Abeni @ 2023-08-22 8:16 UTC (permalink / raw)
To: Arseniy Krasnov, Stefan Hajnoczi, Stefano Garzarella,
David S. Miller, Eric Dumazet, Jakub Kicinski, Michael S. Tsirkin,
Jason Wang, Bobby Eshleman
Cc: kvm, virtualization, netdev, linux-kernel, kernel, oxffffaa
Hi,
I'm sorry for the long delay here. I was OoO in the past few weeks.
On Tue, 2023-08-15 at 00:27 +0300, Arseniy Krasnov wrote:
> 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@sberdevices.ru>
> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
> Changelog:
> v2 -> v3:
> * Comment about 'page_to_virt()' is updated. I don't remove R-b,
> as this change is quiet small I guess.
>
> net/vmw_vsock/virtio_transport.c | 41 +++++++++++++++++++++++++++-----
> 1 file changed, 35 insertions(+), 6 deletions(-)
>
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index e95df847176b..7bbcc8093e51 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -100,7 +100,9 @@ virtio_transport_send_pkt_work(struct work_struct *work)
> vq = vsock->vqs[VSOCK_VQ_TX];
>
> for (;;) {
> - struct scatterlist hdr, buf, *sgs[2];
> + /* +1 is for packet header. */
> + struct scatterlist *sgs[MAX_SKB_FRAGS + 1];
> + struct scatterlist bufs[MAX_SKB_FRAGS + 1];
Note that MAX_SKB_FRAGS depends on a config knob (CONFIG_MAX_SKB_FRAGS)
and valid/reasonable values are up to 45. The total stack usage can be
pretty large (~700 bytes).
As this is under the vsk tx lock, have you considered moving such data
in the virtio_vsock struct?
> int ret, in_sg = 0, out_sg = 0;
> struct sk_buff *skb;
> bool reply;
> @@ -111,12 +113,39 @@ virtio_transport_send_pkt_work(struct work_struct *work)
>
> virtio_transport_deliver_tap_pkt(skb);
> reply = virtio_vsock_skb_reply(skb);
> + sg_init_one(&bufs[out_sg], virtio_vsock_hdr(skb),
> + sizeof(*virtio_vsock_hdr(skb)));
> + sgs[out_sg] = &bufs[out_sg];
> + out_sg++;
> +
> + if (!skb_is_nonlinear(skb)) {
> + if (skb->len > 0) {
> + sg_init_one(&bufs[out_sg], skb->data, skb->len);
> + sgs[out_sg] = &bufs[out_sg];
> + out_sg++;
> + }
> + } else {
> + struct skb_shared_info *si;
> + int i;
> +
> + si = skb_shinfo(skb);
This assumes that the paged skb does not carry any actual data in the
head buffer (only the header). Is that constraint enforced somewhere
else? Otherwise a
WARN_ON_ONCE(skb_headlen(skb) > sizeof(*virtio_vsock_hdr(skb))
could be helpful to catch early possible bugs.
Thanks!
Paolo
> +
> + for (i = 0; i < si->nr_frags; i++) {
> + skb_frag_t *skb_frag = &si->frags[i];
> + void *va;
>
> - 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;
> + /* 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(&bufs[out_sg],
> + va + skb_frag->bv_offset,
> + skb_frag->bv_len);
> + sgs[out_sg] = &bufs[out_sg];
> + out_sg++;
> + }
> }
>
> ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH net-next v6 2/4] vsock/virtio: support to send non-linear skb
2023-08-22 8:16 ` Paolo Abeni
@ 2023-08-23 6:54 ` Arseniy Krasnov
0 siblings, 0 replies; 7+ messages in thread
From: Arseniy Krasnov @ 2023-08-23 6:54 UTC (permalink / raw)
To: Paolo Abeni, Stefan Hajnoczi, Stefano Garzarella, David S. Miller,
Eric Dumazet, Jakub Kicinski, Michael S. Tsirkin, Jason Wang,
Bobby Eshleman
Cc: kvm, virtualization, netdev, linux-kernel, kernel, oxffffaa
On 22.08.2023 11:16, Paolo Abeni wrote:
> Hi,
>
> I'm sorry for the long delay here. I was OoO in the past few weeks.
>
> On Tue, 2023-08-15 at 00:27 +0300, Arseniy Krasnov wrote:
>> 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@sberdevices.ru>
>> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>> ---
>> Changelog:
>> v2 -> v3:
>> * Comment about 'page_to_virt()' is updated. I don't remove R-b,
>> as this change is quiet small I guess.
>>
>> net/vmw_vsock/virtio_transport.c | 41 +++++++++++++++++++++++++++-----
>> 1 file changed, 35 insertions(+), 6 deletions(-)
>>
>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>> index e95df847176b..7bbcc8093e51 100644
>> --- a/net/vmw_vsock/virtio_transport.c
>> +++ b/net/vmw_vsock/virtio_transport.c
>> @@ -100,7 +100,9 @@ virtio_transport_send_pkt_work(struct work_struct *work)
>> vq = vsock->vqs[VSOCK_VQ_TX];
>>
>> for (;;) {
>> - struct scatterlist hdr, buf, *sgs[2];
>> + /* +1 is for packet header. */
>> + struct scatterlist *sgs[MAX_SKB_FRAGS + 1];
>> + struct scatterlist bufs[MAX_SKB_FRAGS + 1];
>
> Note that MAX_SKB_FRAGS depends on a config knob (CONFIG_MAX_SKB_FRAGS)
> and valid/reasonable values are up to 45. The total stack usage can be
> pretty large (~700 bytes).
>
> As this is under the vsk tx lock, have you considered moving such data
> in the virtio_vsock struct?
I think yes, there will be no problem if these temporary variables will be moved
into this global struct. I'll add comment about this reason.
>
>> int ret, in_sg = 0, out_sg = 0;
>> struct sk_buff *skb;
>> bool reply;
>> @@ -111,12 +113,39 @@ virtio_transport_send_pkt_work(struct work_struct *work)
>>
>> virtio_transport_deliver_tap_pkt(skb);
>> reply = virtio_vsock_skb_reply(skb);
>> + sg_init_one(&bufs[out_sg], virtio_vsock_hdr(skb),
>> + sizeof(*virtio_vsock_hdr(skb)));
>> + sgs[out_sg] = &bufs[out_sg];
>> + out_sg++;
>> +
>> + if (!skb_is_nonlinear(skb)) {
>> + if (skb->len > 0) {
>> + sg_init_one(&bufs[out_sg], skb->data, skb->len);
>> + sgs[out_sg] = &bufs[out_sg];
>> + out_sg++;
>> + }
>> + } else {
>> + struct skb_shared_info *si;
>> + int i;
>> +
>> + si = skb_shinfo(skb);
>
> This assumes that the paged skb does not carry any actual data in the
> head buffer (only the header). Is that constraint enforced somewhere
> else? Otherwise a
>
> WARN_ON_ONCE(skb_headlen(skb) > sizeof(*virtio_vsock_hdr(skb))
>
> could be helpful to catch early possible bugs.
Yes, such skbs have data only in paged part, while linear buffer contains only
header. Ok, let's add this warning here to prevent future bugs.
Thanks, Arseniy
>
> Thanks!
>
> Paolo
>
>> +
>> + for (i = 0; i < si->nr_frags; i++) {
>> + skb_frag_t *skb_frag = &si->frags[i];
>> + void *va;
>>
>> - 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;
>> + /* 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(&bufs[out_sg],
>> + va + skb_frag->bv_offset,
>> + skb_frag->bv_len);
>> + sgs[out_sg] = &bufs[out_sg];
>> + out_sg++;
>> + }
>> }
>>
>> ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH net-next v6 3/4] vsock/virtio: non-linear skb handling for tap
2023-08-14 21:27 [PATCH net-next v6 0/4] vsock/virtio/vhost: MSG_ZEROCOPY preparations Arseniy Krasnov
2023-08-14 21:27 ` [PATCH net-next v6 1/4] vsock/virtio/vhost: read data from non-linear skb Arseniy Krasnov
2023-08-14 21:27 ` [PATCH net-next v6 2/4] vsock/virtio: support to send " Arseniy Krasnov
@ 2023-08-14 21:27 ` Arseniy Krasnov
2023-08-14 21:27 ` [PATCH net-next v6 4/4] vsock/virtio: MSG_ZEROCOPY flag support Arseniy Krasnov
3 siblings, 0 replies; 7+ messages in thread
From: Arseniy Krasnov @ 2023-08-14 21:27 UTC (permalink / raw)
To: Stefan Hajnoczi, Stefano Garzarella, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Michael S. Tsirkin,
Jason Wang, Bobby Eshleman
Cc: kvm, virtualization, netdev, linux-kernel, kernel, oxffffaa,
avkrasnov, Arseniy Krasnov
For tap device new skb is created and data from the current skb is
copied to it. This adds copying data from non-linear skb to new
the skb.
Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
---
net/vmw_vsock/virtio_transport_common.c | 31 ++++++++++++++++++++++---
1 file changed, 28 insertions(+), 3 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 3e08d52a9355..3a48e48a99ac 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -106,6 +106,27 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
return NULL;
}
+static void virtio_transport_copy_nonlinear_skb(const struct sk_buff *skb,
+ void *dst,
+ size_t len)
+{
+ struct iov_iter iov_iter = { 0 };
+ struct kvec kvec;
+ size_t to_copy;
+
+ kvec.iov_base = dst;
+ kvec.iov_len = len;
+
+ iov_iter.iter_type = ITER_KVEC;
+ iov_iter.kvec = &kvec;
+ iov_iter.nr_segs = 1;
+
+ to_copy = min_t(size_t, len, skb->len);
+
+ skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->offset,
+ &iov_iter, to_copy);
+}
+
/* Packet capture */
static struct sk_buff *virtio_transport_build_skb(void *opaque)
{
@@ -114,7 +135,6 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
struct af_vsockmon_hdr *hdr;
struct sk_buff *skb;
size_t payload_len;
- void *payload_buf;
/* A packet could be split to fit the RX buffer, so we can retrieve
* the payload length from the header and the buffer pointer taking
@@ -122,7 +142,6 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
*/
pkt_hdr = virtio_vsock_hdr(pkt);
payload_len = pkt->len;
- payload_buf = pkt->data;
skb = alloc_skb(sizeof(*hdr) + sizeof(*pkt_hdr) + payload_len,
GFP_ATOMIC);
@@ -165,7 +184,13 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
skb_put_data(skb, pkt_hdr, sizeof(*pkt_hdr));
if (payload_len) {
- skb_put_data(skb, payload_buf, payload_len);
+ if (skb_is_nonlinear(pkt)) {
+ void *data = skb_put(skb, payload_len);
+
+ virtio_transport_copy_nonlinear_skb(pkt, data, payload_len);
+ } else {
+ skb_put_data(skb, pkt->data, payload_len);
+ }
}
return skb;
--
2.25.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH net-next v6 4/4] vsock/virtio: MSG_ZEROCOPY flag support
2023-08-14 21:27 [PATCH net-next v6 0/4] vsock/virtio/vhost: MSG_ZEROCOPY preparations Arseniy Krasnov
` (2 preceding siblings ...)
2023-08-14 21:27 ` [PATCH net-next v6 3/4] vsock/virtio: non-linear skb handling for tap Arseniy Krasnov
@ 2023-08-14 21:27 ` Arseniy Krasnov
3 siblings, 0 replies; 7+ messages in thread
From: Arseniy Krasnov @ 2023-08-14 21:27 UTC (permalink / raw)
To: Stefan Hajnoczi, Stefano Garzarella, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Michael S. Tsirkin,
Jason Wang, Bobby Eshleman
Cc: kvm, virtualization, netdev, linux-kernel, kernel, oxffffaa,
avkrasnov, Arseniy Krasnov
This adds handling of MSG_ZEROCOPY flag on transmission path: if this
flag is set and zerocopy transmission is possible (enabled in socket
options and transport allows zerocopy), then non-linear skb will be
created and filled with the pages of user's buffer. Pages of user's
buffer are locked in memory by 'get_user_pages()'. Second thing that
this patch does is replace type of skb owning: instead of calling
'skb_set_owner_sk_safe()' it calls 'skb_set_owner_w()'. Reason of this
change is that '__zerocopy_sg_from_iter()' increments 'sk_wmem_alloc'
of socket, so to decrease this field correctly proper skb destructor is
needed: 'sock_wfree()'. This destructor is set by 'skb_set_owner_w()'.
Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
Changelog:
v5(big patchset) -> v1:
* Refactorings of 'if' conditions.
* Remove extra blank line.
* Remove 'frag_off' field unneeded init.
* Add function 'virtio_transport_fill_skb()' which fills both linear
and non-linear skb with provided data.
v1 -> v2:
* Use original order of last four arguments in 'virtio_transport_alloc_skb()'.
v2 -> v3:
* Add new transport callback: 'msgzerocopy_check_iov'. It checks that
provided 'iov_iter' with data could be sent in a zerocopy mode.
If this callback is not set in transport - transport allows to send
any 'iov_iter' in zerocopy mode. Otherwise - if callback returns 'true'
then zerocopy is allowed. Reason of this callback is that in case of
G2H transmission we insert whole skb to the tx virtio queue and such
skb must fit to the size of the virtio queue to be sent in a single
iteration (may be tx logic in 'virtio_transport.c' could be reworked
as in vhost to support partial send of current skb). This callback
will be enabled only for G2H path. For details pls see comment
'Check that tx queue...' below.
v3 -> v4:
* 'msgzerocopy_check_iov' moved from 'struct vsock_transport' to
'struct virtio_transport' as it is virtio specific callback and
never needed in other transports.
v4 -> v5:
* 'msgzerocopy_check_iov' renamed to 'can_msgzerocopy' and now it
uses number of buffers to send as input argument. I think there is
no need to pass iov to this callback (at least today, it is used only
by guest side of virtio transport), because the only thing that this
callback does is comparison of number of buffers to be inserted to
the tx queue and size of this queue.
* Remove any checks for type of current 'iov_iter' with payload (is it
'iovec' or 'ubuf'). These checks left from the earlier versions where I
didn't use already implemented kernel API which handles every type of
'iov_iter'.
v5 -> v6:
* Refactor 'virtio_transport_fill_skb()'.
* Add 'WARN_ON_ONCE()' and comment on invalid combination of destination
socket and payload in 'virtio_transport_alloc_skb()'.
include/linux/virtio_vsock.h | 5 +
net/vmw_vsock/virtio_transport.c | 33 ++++
net/vmw_vsock/virtio_transport_common.c | 250 ++++++++++++++++++------
3 files changed, 231 insertions(+), 57 deletions(-)
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index a91fbdf233e4..56501cd9843f 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -160,6 +160,11 @@ struct virtio_transport {
/* Takes ownership of the packet */
int (*send_pkt)(struct sk_buff *skb);
+
+ /* Used in MSG_ZEROCOPY mode. Checks that provided data
+ * could be transmitted with zerocopy mode.
+ */
+ bool (*can_msgzerocopy)(int bufs_num);
};
ssize_t
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index 7bbcc8093e51..eae7758dce56 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -442,6 +442,38 @@ static void virtio_vsock_rx_done(struct virtqueue *vq)
queue_work(virtio_vsock_workqueue, &vsock->rx_work);
}
+static bool virtio_transport_can_msgzerocopy(int bufs_num)
+{
+ struct virtio_vsock *vsock;
+ bool res = false;
+
+ rcu_read_lock();
+
+ vsock = rcu_dereference(the_virtio_vsock);
+ if (vsock) {
+ struct virtqueue *vq = vsock->vqs[VSOCK_VQ_TX];
+
+ /* Check that tx queue is large enough to keep whole
+ * data to send. This is needed, because when there is
+ * not enough free space in the queue, current skb to
+ * send will be reinserted to the head of tx list of
+ * the socket to retry transmission later, so if skb
+ * is bigger than whole queue, it will be reinserted
+ * again and again, thus blocking other skbs to be sent.
+ * Each page of the user provided buffer will be added
+ * as a single buffer to the tx virtqueue, so compare
+ * number of pages against maximum capacity of the queue.
+ * +1 means buffer for the packet header.
+ */
+ if (bufs_num + 1 <= vq->num_max)
+ res = true;
+ }
+
+ rcu_read_unlock();
+
+ return res;
+}
+
static bool virtio_transport_seqpacket_allow(u32 remote_cid);
static struct virtio_transport virtio_transport = {
@@ -491,6 +523,7 @@ static struct virtio_transport virtio_transport = {
},
.send_pkt = virtio_transport_send_pkt,
+ .can_msgzerocopy = virtio_transport_can_msgzerocopy,
};
static bool virtio_transport_seqpacket_allow(u32 remote_cid)
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 3a48e48a99ac..7f42ad131a69 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -37,27 +37,99 @@ virtio_transport_get_ops(struct vsock_sock *vsk)
return container_of(t, struct virtio_transport, transport);
}
-/* Returns a new packet on success, otherwise returns NULL.
- *
- * If NULL is returned, errp is set to a negative errno.
- */
-static struct sk_buff *
-virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
- size_t len,
- u32 src_cid,
- u32 src_port,
- u32 dst_cid,
- u32 dst_port)
-{
- const size_t skb_len = VIRTIO_VSOCK_SKB_HEADROOM + len;
- struct virtio_vsock_hdr *hdr;
- struct sk_buff *skb;
+static bool virtio_transport_can_zcopy(struct virtio_vsock_pkt_info *info,
+ size_t max_to_send)
+{
+ const struct virtio_transport *t_ops;
+ struct iov_iter *iov_iter;
+
+ if (!info->msg)
+ return false;
+
+ iov_iter = &info->msg->msg_iter;
+
+ if (iov_iter->iov_offset)
+ return false;
+
+ /* We can't send whole iov. */
+ if (iov_iter->count > max_to_send)
+ return false;
+
+ /* Check that transport can send data in zerocopy mode. */
+ t_ops = virtio_transport_get_ops(info->vsk);
+
+ if (t_ops->can_msgzerocopy) {
+ int pages_in_iov = iov_iter_npages(iov_iter, MAX_SKB_FRAGS);
+ int pages_to_send = min(pages_in_iov, MAX_SKB_FRAGS);
+
+ return t_ops->can_msgzerocopy(pages_to_send);
+ }
+
+ return true;
+}
+
+static int virtio_transport_init_zcopy_skb(struct vsock_sock *vsk,
+ struct sk_buff *skb,
+ struct msghdr *msg,
+ bool zerocopy)
+{
+ struct ubuf_info *uarg;
+
+ if (msg->msg_ubuf) {
+ uarg = msg->msg_ubuf;
+ net_zcopy_get(uarg);
+ } else {
+ struct iov_iter *iter = &msg->msg_iter;
+ struct ubuf_info_msgzc *uarg_zc;
+
+ uarg = msg_zerocopy_realloc(sk_vsock(vsk),
+ iter->count,
+ NULL);
+ if (!uarg)
+ return -1;
+
+ uarg_zc = uarg_to_msgzc(uarg);
+ uarg_zc->zerocopy = zerocopy ? 1 : 0;
+ }
+
+ skb_zcopy_init(skb, uarg);
+
+ return 0;
+}
+
+static int virtio_transport_fill_skb(struct sk_buff *skb,
+ struct virtio_vsock_pkt_info *info,
+ size_t len,
+ bool zcopy)
+{
void *payload;
int err;
- skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL);
- if (!skb)
- return NULL;
+ if (zcopy)
+ return __zerocopy_sg_from_iter(info->msg, NULL, skb,
+ &info->msg->msg_iter,
+ len);
+
+ payload = skb_put(skb, len);
+ err = memcpy_from_msg(payload, info->msg, len);
+ if (err)
+ return -1;
+
+ if (msg_data_left(info->msg))
+ return 0;
+
+ return 0;
+}
+
+static void virtio_transport_init_hdr(struct sk_buff *skb,
+ struct virtio_vsock_pkt_info *info,
+ u32 src_cid,
+ u32 src_port,
+ u32 dst_cid,
+ u32 dst_port,
+ size_t len)
+{
+ struct virtio_vsock_hdr *hdr;
hdr = virtio_vsock_hdr(skb);
hdr->type = cpu_to_le16(info->type);
@@ -68,42 +140,6 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
hdr->dst_port = cpu_to_le32(dst_port);
hdr->flags = cpu_to_le32(info->flags);
hdr->len = cpu_to_le32(len);
-
- if (info->msg && len > 0) {
- payload = skb_put(skb, len);
- err = memcpy_from_msg(payload, info->msg, len);
- if (err)
- goto out;
-
- if (msg_data_left(info->msg) == 0 &&
- info->type == VIRTIO_VSOCK_TYPE_SEQPACKET) {
- hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
-
- if (info->msg->msg_flags & MSG_EOR)
- hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
- }
- }
-
- if (info->reply)
- virtio_vsock_skb_set_reply(skb);
-
- trace_virtio_transport_alloc_pkt(src_cid, src_port,
- dst_cid, dst_port,
- len,
- info->type,
- info->op,
- info->flags);
-
- if (info->vsk && !skb_set_owner_sk_safe(skb, sk_vsock(info->vsk))) {
- WARN_ONCE(1, "failed to allocate skb on vsock socket with sk_refcnt == 0\n");
- goto out;
- }
-
- return skb;
-
-out:
- kfree_skb(skb);
- return NULL;
}
static void virtio_transport_copy_nonlinear_skb(const struct sk_buff *skb,
@@ -214,6 +250,78 @@ static u16 virtio_transport_get_type(struct sock *sk)
return VIRTIO_VSOCK_TYPE_SEQPACKET;
}
+static struct sk_buff *virtio_transport_alloc_skb(struct vsock_sock *vsk,
+ struct virtio_vsock_pkt_info *info,
+ size_t payload_len,
+ bool zcopy,
+ u32 src_cid,
+ u32 src_port,
+ u32 dst_cid,
+ u32 dst_port)
+{
+ struct sk_buff *skb;
+ size_t skb_len;
+
+ skb_len = VIRTIO_VSOCK_SKB_HEADROOM;
+
+ if (!zcopy)
+ skb_len += payload_len;
+
+ skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL);
+ if (!skb)
+ return NULL;
+
+ virtio_transport_init_hdr(skb, info, src_cid, src_port,
+ dst_cid, dst_port,
+ payload_len);
+
+ /* If 'vsk' != NULL then payload is always present, so we
+ * will never call '__zerocopy_sg_from_iter()' below without
+ * setting skb owner in 'skb_set_owner_w()'. The only case
+ * when 'vsk' == NULL is VIRTIO_VSOCK_OP_RST control message
+ * without payload.
+ */
+ WARN_ON_ONCE(!(vsk && (info->msg && payload_len)) && zcopy);
+
+ /* Set owner here, because '__zerocopy_sg_from_iter()' uses
+ * owner of skb without check to update 'sk_wmem_alloc'.
+ */
+ if (vsk)
+ skb_set_owner_w(skb, sk_vsock(vsk));
+
+ if (info->msg && payload_len > 0) {
+ int err;
+
+ err = virtio_transport_fill_skb(skb, info, payload_len, zcopy);
+ if (err)
+ goto out;
+
+ if (info->type == VIRTIO_VSOCK_TYPE_SEQPACKET) {
+ struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
+
+ hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
+
+ if (info->msg->msg_flags & MSG_EOR)
+ hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
+ }
+ }
+
+ if (info->reply)
+ virtio_vsock_skb_set_reply(skb);
+
+ trace_virtio_transport_alloc_pkt(src_cid, src_port,
+ dst_cid, dst_port,
+ payload_len,
+ info->type,
+ info->op,
+ info->flags);
+
+ return skb;
+out:
+ kfree_skb(skb);
+ return NULL;
+}
+
/* This function can only be used on connecting/connected sockets,
* since a socket assigned to a transport is required.
*
@@ -222,10 +330,12 @@ static u16 virtio_transport_get_type(struct sock *sk)
static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
struct virtio_vsock_pkt_info *info)
{
+ u32 max_skb_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
u32 src_cid, src_port, dst_cid, dst_port;
const struct virtio_transport *t_ops;
struct virtio_vsock_sock *vvs;
u32 pkt_len = info->pkt_len;
+ bool can_zcopy = false;
u32 rest_len;
int ret;
@@ -254,15 +364,30 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
return pkt_len;
+ if (info->msg) {
+ /* If zerocopy is not enabled by 'setsockopt()', we behave as
+ * there is no MSG_ZEROCOPY flag set.
+ */
+ if (!sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY))
+ info->msg->msg_flags &= ~MSG_ZEROCOPY;
+
+ if (info->msg->msg_flags & MSG_ZEROCOPY)
+ can_zcopy = virtio_transport_can_zcopy(info, pkt_len);
+
+ if (can_zcopy)
+ max_skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE,
+ (MAX_SKB_FRAGS * PAGE_SIZE));
+ }
+
rest_len = pkt_len;
do {
struct sk_buff *skb;
size_t skb_len;
- skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, rest_len);
+ skb_len = min(max_skb_len, rest_len);
- skb = virtio_transport_alloc_skb(info, skb_len,
+ skb = virtio_transport_alloc_skb(vsk, info, skb_len, can_zcopy,
src_cid, src_port,
dst_cid, dst_port);
if (!skb) {
@@ -270,6 +395,17 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
break;
}
+ /* This is last skb to send this portion of data. */
+ if (info->msg && info->msg->msg_flags & MSG_ZEROCOPY &&
+ skb_len == rest_len && info->op == VIRTIO_VSOCK_OP_RW) {
+ if (virtio_transport_init_zcopy_skb(vsk, skb,
+ info->msg,
+ can_zcopy)) {
+ ret = -ENOMEM;
+ break;
+ }
+ }
+
virtio_transport_inc_tx_pkt(vvs, skb);
ret = t_ops->send_pkt(skb);
@@ -985,7 +1121,7 @@ static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
if (!t)
return -ENOTCONN;
- reply = virtio_transport_alloc_skb(&info, 0,
+ reply = virtio_transport_alloc_skb(NULL, &info, 0, false,
le64_to_cpu(hdr->dst_cid),
le32_to_cpu(hdr->dst_port),
le64_to_cpu(hdr->src_cid),
--
2.25.1
^ permalink raw reply related [flat|nested] 7+ messages in thread