On 16.02.2023 17:09, Stefano Garzarella wrote:
> 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@xxxxxxxxxxxxxx>
>> ---
>> 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?
I see
>
> 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
>
