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Message-ID: <cgq3d3j25doy7qar6xsepsrly5ypyjwahf2gybfi3fnozp3kjx@hh5q5bps37ws>
Date: Thu, 6 Jul 2023 18:49:06 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
Cc: Stefan Hajnoczi <stefanha@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Bobby Eshleman <bobby.eshleman@...edance.com>,
kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
kernel@...rdevices.ru, oxffffaa@...il.com
Subject: Re: [RFC PATCH v5 02/17] vhost/vsock: read data from non-linear skb
On Sat, Jul 01, 2023 at 09:39:32AM +0300, Arseniy Krasnov wrote:
>This adds copying to guest's virtio buffers from non-linear skbs. Such
>skbs are created by protocol layer when MSG_ZEROCOPY flags is used. It
>replaces call of 'copy_to_iter()' to 'skb_copy_datagram_iter()'- second
>function can read data from non-linear skb. Also this patch uses field
>'frag_off' from skb control block. This field shows current offset to
>read data from skb which could be both linear or not.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>---
> Changelog:
> v4 -> v5:
> * Use local variable for 'frag_off'.
> * Update commit message by adding some details about 'frag_off' field.
> * R-b from Bobby Eshleman removed due to patch update.
I think we should merge this patch with the previous one, since
vhost-vsock for example uses virtio_transport_stream_do_dequeue()
that we change in the previous commit, so we will break the bisection.
The patch LGTM!
Stefano
>
> drivers/vhost/vsock.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index 6578db78f0ae..cb00e0e059e4 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 frag_off;
> 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;
>+ frag_off = VIRTIO_VSOCK_SKB_CB(skb)->frag_off;
>+ payload_len = skb->len - frag_off;
> 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,
>+ frag_off,
>+ &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)->frag_off += 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)->frag_off < skb->len) {
> hdr->flags |= cpu_to_le32(flags_to_restore);
>
> /* We are queueing the same skb to handle
>--
>2.25.1
>
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