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Message-ID: <20230216140917.jpcmfrwl5gpdzdzi@sgarzare-redhat>
Date: Thu, 16 Feb 2023 15:09:17 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
Cc: Stefan Hajnoczi <stefanha@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Krasnov Arseniy <oxffffaa@...il.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"virtualization@...ts.linux-foundation.org"
<virtualization@...ts.linux-foundation.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
kernel <kernel@...rdevices.ru>
Subject: Re: [RFC PATCH v1 04/12] vhost/vsock: non-linear skb handling support
On Mon, Feb 06, 2023 at 06:57:16AM +0000, 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.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>---
> drivers/vhost/vsock.c | 56 ++++++++++++++++++++++++++++++++----
> include/linux/virtio_vsock.h | 12 ++++++++
> 2 files changed, 63 insertions(+), 5 deletions(-)
>
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index 1f3b89c885cc..60b9cafa3e31 100644
>--- a/drivers/vhost/vsock.c
>+++ b/drivers/vhost/vsock.c
>@@ -86,6 +86,44 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
> return NULL;
> }
>
>+static int vhost_transport_copy_nonlinear_skb(struct sk_buff *skb,
>+ struct iov_iter *iov_iter,
>+ size_t len)
>+{
>+ size_t rest_len = len;
>+
>+ while (rest_len && virtio_vsock_skb_has_frags(skb)) {
>+ struct bio_vec *curr_vec;
>+ size_t curr_vec_end;
>+ size_t to_copy;
>+ int curr_frag;
>+ int curr_offs;
>+
>+ curr_frag = VIRTIO_VSOCK_SKB_CB(skb)->curr_frag;
>+ curr_offs = VIRTIO_VSOCK_SKB_CB(skb)->frag_off;
>+ curr_vec = &skb_shinfo(skb)->frags[curr_frag];
>+
>+ curr_vec_end = curr_vec->bv_offset + curr_vec->bv_len;
>+ to_copy = min(rest_len, (size_t)(curr_vec_end - curr_offs));
>+
>+ if (copy_page_to_iter(curr_vec->bv_page, curr_offs,
>+ to_copy, iov_iter) != to_copy)
>+ return -1;
>+
>+ rest_len -= to_copy;
>+ VIRTIO_VSOCK_SKB_CB(skb)->frag_off += to_copy;
>+
>+ if (VIRTIO_VSOCK_SKB_CB(skb)->frag_off == (curr_vec_end)) {
>+ VIRTIO_VSOCK_SKB_CB(skb)->curr_frag++;
>+ VIRTIO_VSOCK_SKB_CB(skb)->frag_off = 0;
>+ }
>+ }
Can it happen that we exit this loop and rest_len is not 0?
In this case, is it correct to decrement data_len by len?
Thanks,
Stefano
>+
>+ skb->data_len -= len;
>+
>+ return 0;
>+}
>+
> static void
> vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> struct vhost_virtqueue *vq)
>@@ -197,11 +235,19 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> break;
> }
>
>- nbytes = copy_to_iter(skb->data, payload_len, &iov_iter);
>- if (nbytes != payload_len) {
>- kfree_skb(skb);
>- vq_err(vq, "Faulted on copying pkt buf\n");
>- break;
>+ if (skb_is_nonlinear(skb)) {
>+ if (vhost_transport_copy_nonlinear_skb(skb, &iov_iter,
>+ payload_len)) {
>+ vq_err(vq, "Faulted on copying pkt buf from page\n");
>+ break;
>+ }
>+ } else {
>+ nbytes = copy_to_iter(skb->data, payload_len, &iov_iter);
>+ if (nbytes != payload_len) {
>+ kfree_skb(skb);
>+ vq_err(vq, "Faulted on copying pkt buf\n");
>+ break;
>+ }
> }
>
> /* Deliver to monitoring devices all packets that we
>diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>index 3f9c16611306..e7efdb78ce6e 100644
>--- a/include/linux/virtio_vsock.h
>+++ b/include/linux/virtio_vsock.h
>@@ -12,6 +12,10 @@
> struct virtio_vsock_skb_cb {
> bool reply;
> bool tap_delivered;
>+ /* Current fragment in 'frags' of skb. */
>+ u32 curr_frag;
>+ /* Offset from 0 in current fragment. */
>+ u32 frag_off;
> };
>
> #define VIRTIO_VSOCK_SKB_CB(skb) ((struct virtio_vsock_skb_cb *)((skb)->cb))
>@@ -46,6 +50,14 @@ static inline void virtio_vsock_skb_clear_tap_delivered(struct sk_buff *skb)
> VIRTIO_VSOCK_SKB_CB(skb)->tap_delivered = false;
> }
>
>+static inline bool virtio_vsock_skb_has_frags(struct sk_buff *skb)
>+{
>+ if (!skb_is_nonlinear(skb))
>+ return false;
>+
>+ return VIRTIO_VSOCK_SKB_CB(skb)->curr_frag != skb_shinfo(skb)->nr_frags;
>+}
>+
> static inline void virtio_vsock_skb_rx_put(struct sk_buff *skb)
> {
> u32 len;
>--
>2.25.1
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