user/sven/linux.git/include/linux/virtio_vsock.h, branch v6.12.48

vsock/virtio: Resize receive buffers so that each SKB fits in a 4K page

2025-08-20T16:30:40Z

[ Upstream commit 03a92f036a04fed2b00d69f5f46f1a486e70dc5c ] When allocating receive buffers for the vsock virtio RX virtqueue, an SKB is allocated with a 4140 data payload (the 44-byte packet header + VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE). Even when factoring in the SKB overhead, the resulting 8KiB allocation thanks to the rounding in kmalloc_reserve() is wasteful (~3700 unusable bytes) and results in a higher-order page allocation on systems with 4KiB pages just for the sake of a few hundred bytes of packet data. Limit the vsock virtio RX buffers to 4KiB per SKB, resulting in much better memory utilisation and removing the need to allocate higher-order pages entirely. Reviewed-by: Stefano Garzarella Signed-off-by: Will Deacon Message-Id: <20250717090116.11987-5-will@kernel.org> Signed-off-by: Michael S. Tsirkin Signed-off-by: Sasha Levin

vsock/virtio: fix `rx_bytes` accounting for stream sockets

2025-06-19T13:31:54Z

[ Upstream commit 45ca7e9f0730ae36fc610e675b990e9cc9ca0714 ] In `struct virtio_vsock_sock`, we maintain two counters: - `rx_bytes`: used internally to track how many bytes have been read. This supports mechanisms like .stream_has_data() and sock_rcvlowat(). - `fwd_cnt`: used for the credit mechanism to inform available receive buffer space to the remote peer. These counters are updated via virtio_transport_inc_rx_pkt() and virtio_transport_dec_rx_pkt(). Since the beginning with commit 06a8fc78367d ("VSOCK: Introduce virtio_vsock_common.ko"), we call virtio_transport_dec_rx_pkt() in virtio_transport_stream_do_dequeue() only when we consume the entire packet, so partial reads, do not update `rx_bytes` and `fwd_cnt`. This is fine for `fwd_cnt`, because we still have space used for the entire packet, and we don't want to update the credit for the other peer until we free the space of the entire packet. However, this causes `rx_bytes` to be stale on partial reads. Previously, this didn’t cause issues because `rx_bytes` was used only by .stream_has_data(), and any unread portion of a packet implied data was still available. However, since commit 93b808876682 ("virtio/vsock: fix logic which reduces credit update messages"), we now rely on `rx_bytes` to determine if a credit update should be sent when the data in the RX queue drops below SO_RCVLOWAT value. This patch fixes the accounting by updating `rx_bytes` with the number of bytes actually read, even on partial reads, while leaving `fwd_cnt` untouched until the packet is fully consumed. Also introduce a new `buf_used` counter to check that the remote peer is honoring the given credit; this was previously done via `rx_bytes`. Fixes: 93b808876682 ("virtio/vsock: fix logic which reduces credit update messages") Signed-off-by: Stefano Garzarella Link: https://patch.msgid.link/20250521121705.196379-1-sgarzare@redhat.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

vsock/virtio: add SIOCOUTQ support for all virtio based transports

2024-08-02T08:20:28Z

Introduce support for virtio_transport_unsent_bytes ioctl for virtio_transport, vhost_vsock and vsock_loopback. For all transports the unsent bytes counter is incremented in virtio_transport_get_credit. In virtio_transport (G2H) and in vhost-vsock (H2G) the counter is decremented when the skbuff is consumed. In vsock_loopback the same skbuff is passed from the transmitter to the receiver, so the counter is decremented before queuing the skbuff to the receiver. Signed-off-by: Luigi Leonardi Reviewed-by: Stefano Garzarella Signed-off-by: David S. Miller

virtio/vsock: send credit update during setting SO_RCVLOWAT

2023-12-15T10:37:35Z

Send credit update message when SO_RCVLOWAT is updated and it is bigger than number of bytes in rx queue. It is needed, because 'poll()' will wait until number of bytes in rx queue will be not smaller than O_RCVLOWAT, so kick sender to send more data. Otherwise mutual hungup for tx/rx is possible: sender waits for free space and receiver is waiting data in 'poll()'. Rename 'set_rcvlowat' callback to 'notify_set_rcvlowat' and set 'sk->sk_rcvlowat' only in one place (i.e. 'vsock_set_rcvlowat'), so the transport doesn't need to do it. Fixes: b89d882dc9fc ("vsock/virtio: reduce credit update messages") Signed-off-by: Arseniy Krasnov Reviewed-by: Stefano Garzarella Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller

vsock/virtio: MSG_ZEROCOPY flag support

2023-09-21T10:34:00Z

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

vsock/virtio/vhost: read data from non-linear skb

2023-09-21T10:34:00Z

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

vsock: support sockmap

2023-03-29T07:19:38Z

This patch adds sockmap support for vsock sockets. It is intended to be usable by all transports, but only the virtio and loopback transports are implemented. SOCK_STREAM, SOCK_DGRAM, and SOCK_SEQPACKET are all supported. Signed-off-by: Bobby Eshleman Acked-by: Michael S. Tsirkin Reviewed-by: Stefano Garzarella Signed-off-by: David S. Miller

virtio/vsock: replace virtio_vsock_pkt with sk_buff

2023-01-16T13:26:33Z

This commit changes virtio/vsock to use sk_buff instead of virtio_vsock_pkt. Beyond better conforming to other net code, using sk_buff allows vsock to use sk_buff-dependent features in the future (such as sockmap) and improves throughput. This patch introduces the following performance changes: Tool: Uperf Env: Phys Host + L1 Guest Payload: 64k Threads: 16 Test Runs: 10 Type: SOCK_STREAM Before: commit b7bfaa761d760 ("Linux 6.2-rc3") Before ------ g2h: 16.77Gb/s h2g: 10.56Gb/s After ----- g2h: 21.04Gb/s h2g: 10.76Gb/s Signed-off-by: Bobby Eshleman Reviewed-by: Stefano Garzarella Signed-off-by: David S. Miller

virtio/vsock: rest of SOCK_SEQPACKET support

2021-06-11T20:32:47Z

Small updates to make SOCK_SEQPACKET work: 1) Send SHUTDOWN on socket close for SEQPACKET type. 2) Set SEQPACKET packet type during send. 3) Set 'VIRTIO_VSOCK_SEQ_EOR' bit in flags for last packet of message. 4) Implement data check function for SEQPACKET. 5) Check for max datagram size. Signed-off-by: Arseny Krasnov Signed-off-by: David S. Miller

virtio/vsock: dequeue callback for SOCK_SEQPACKET

2021-06-11T20:32:47Z

Callback fetches RW packets from rx queue of socket until whole record is copied(if user's buffer is full, user is not woken up). This is done to not stall sender, because if we wake up user and it leaves syscall, nobody will send credit update for rest of record, and sender will wait for next enter of read syscall at receiver's side. So if user buffer is full, we just send credit update and drop data. Signed-off-by: Arseny Krasnov Signed-off-by: David S. Miller