From 0df7cd3c13e44d01f9f28e29cbce74e2931b00fe Mon Sep 17 00:00:00 2001 From: Arseniy Krasnov Date: Sat, 16 Sep 2023 16:09:15 +0300 Subject: vsock/virtio/vhost: read data from non-linear skb 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 Reviewed-by: Stefano Garzarella Acked-by: Michael S. Tsirkin Signed-off-by: Paolo Abeni --- include/linux/virtio_vsock.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') 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)) -- cgit v1.2.3 From 581512a6dc939ef122e49336626ae159f3b8a345 Mon Sep 17 00:00:00 2001 From: Arseniy Krasnov Date: Sat, 16 Sep 2023 16:09:18 +0300 Subject: vsock/virtio: MSG_ZEROCOPY flag support This adds handling of MSG_ZEROCOPY flag on transmission path: 1) 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()'. 2) Replaces way of skb owning: instead of '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()'. 3) Adds new callback to 'struct virtio_transport': 'can_msgzerocopy'. If this callback is set, then transport needs extra check to be able to send provided number of buffers in zerocopy mode. Currently, the only transport that needs this callback set is virtio, because this transport adds new buffers to the virtio queue and we need to check, that number of these buffers is less than size of the queue (it is required by virtio spec). vhost and loopback transports don't need this check. Signed-off-by: Arseniy Krasnov Reviewed-by: Stefano Garzarella Acked-by: Michael S. Tsirkin Signed-off-by: Paolo Abeni --- include/linux/virtio_vsock.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux') diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h index a91fbdf233e4..ebb3ce63d64d 100644 --- a/include/linux/virtio_vsock.h +++ b/include/linux/virtio_vsock.h @@ -160,6 +160,15 @@ struct virtio_transport { /* Takes ownership of the packet */ int (*send_pkt)(struct sk_buff *skb); + + /* Used in MSG_ZEROCOPY mode. Checks, that provided data + * (number of buffers) could be transmitted with zerocopy + * mode. If this callback is not implemented for the current + * transport - this means that this transport doesn't need + * extra checks and can perform zerocopy transmission by + * default. + */ + bool (*can_msgzerocopy)(int bufs_num); }; ssize_t -- cgit v1.2.3