Michael S. Tsirkin
2023-Jul-25 13:36 UTC
[PATCH net-next v3 4/4] vsock/virtio: MSG_ZEROCOPY flag support
On Tue, Jul 25, 2023 at 04:28:14PM +0300, Arseniy Krasnov wrote:> > > On 25.07.2023 16:22, Michael S. Tsirkin wrote: > > On Tue, Jul 25, 2023 at 04:04:13PM +0300, Arseniy Krasnov wrote: > >> > >> > >> On 25.07.2023 14:50, Michael S. Tsirkin wrote: > >>> On Fri, Jul 21, 2023 at 08:09:03AM +0300, Arseniy Krasnov wrote: > >>>> > >>>> > >>>> On 21.07.2023 00:42, Arseniy Krasnov wrote: > >>>>> This adds handling of MSG_ZEROCOPY flag on transmission path: 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()'. Second thing that > >>>>> this patch does is replace type of skb owning: instead of calling > >>>>> '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()'. > >>>>> > >>>>> Signed-off-by: Arseniy Krasnov <AVKrasnov at sberdevices.ru> > >>>>> --- > >>>>> Changelog: > >>>>> v5(big patchset) -> v1: > >>>>> * Refactorings of 'if' conditions. > >>>>> * Remove extra blank line. > >>>>> * Remove 'frag_off' field unneeded init. > >>>>> * Add function 'virtio_transport_fill_skb()' which fills both linear > >>>>> and non-linear skb with provided data. > >>>>> v1 -> v2: > >>>>> * Use original order of last four arguments in 'virtio_transport_alloc_skb()'. > >>>>> v2 -> v3: > >>>>> * Add new transport callback: 'msgzerocopy_check_iov'. It checks that > >>>>> provided 'iov_iter' with data could be sent in a zerocopy mode. > >>>>> If this callback is not set in transport - transport allows to send > >>>>> any 'iov_iter' in zerocopy mode. Otherwise - if callback returns 'true' > >>>>> then zerocopy is allowed. Reason of this callback is that in case of > >>>>> G2H transmission we insert whole skb to the tx virtio queue and such > >>>>> skb must fit to the size of the virtio queue to be sent in a single > >>>>> iteration (may be tx logic in 'virtio_transport.c' could be reworked > >>>>> as in vhost to support partial send of current skb). This callback > >>>>> will be enabled only for G2H path. For details pls see comment > >>>>> 'Check that tx queue...' below. > >>>>> > >>>>> include/net/af_vsock.h | 3 + > >>>>> net/vmw_vsock/virtio_transport.c | 39 ++++ > >>>>> net/vmw_vsock/virtio_transport_common.c | 257 ++++++++++++++++++------ > >>>>> 3 files changed, 241 insertions(+), 58 deletions(-) > >>>>> > >>>>> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h > >>>>> index 0e7504a42925..a6b346eeeb8e 100644 > >>>>> --- a/include/net/af_vsock.h > >>>>> +++ b/include/net/af_vsock.h > >>>>> @@ -177,6 +177,9 @@ struct vsock_transport { > >>>>> > >>>>> /* Read a single skb */ > >>>>> int (*read_skb)(struct vsock_sock *, skb_read_actor_t); > >>>>> + > >>>>> + /* Zero-copy. */ > >>>>> + bool (*msgzerocopy_check_iov)(const struct iov_iter *); > >>>>> }; > >>>>> > >>>>> /**** CORE ****/ > >>>>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c > >>>>> index 7bbcc8093e51..23cb8ed638c4 100644 > >>>>> --- a/net/vmw_vsock/virtio_transport.c > >>>>> +++ b/net/vmw_vsock/virtio_transport.c > >>>>> @@ -442,6 +442,43 @@ static void virtio_vsock_rx_done(struct virtqueue *vq) > >>>>> queue_work(virtio_vsock_workqueue, &vsock->rx_work); > >>>>> } > >>>>> > >>>>> +static bool virtio_transport_msgzerocopy_check_iov(const struct iov_iter *iov) > >>>>> +{ > >>>>> + struct virtio_vsock *vsock; > >>>>> + bool res = false; > >>>>> + > >>>>> + rcu_read_lock(); > >>>>> + > >>>>> + vsock = rcu_dereference(the_virtio_vsock); > >>>>> + if (vsock) { > >>>>> + struct virtqueue *vq; > >>>>> + int iov_pages; > >>>>> + > >>>>> + vq = vsock->vqs[VSOCK_VQ_TX]; > >>>>> + > >>>>> + iov_pages = round_up(iov->count, PAGE_SIZE) / PAGE_SIZE; > >>>>> + > >>>>> + /* Check that tx queue is large enough to keep whole > >>>>> + * data to send. This is needed, because when there is > >>>>> + * not enough free space in the queue, current skb to > >>>>> + * send will be reinserted to the head of tx list of > >>>>> + * the socket to retry transmission later, so if skb > >>>>> + * is bigger than whole queue, it will be reinserted > >>>>> + * again and again, thus blocking other skbs to be sent. > >>>>> + * Each page of the user provided buffer will be added > >>>>> + * as a single buffer to the tx virtqueue, so compare > >>>>> + * number of pages against maximum capacity of the queue. > >>>>> + * +1 means buffer for the packet header. > >>>>> + */ > >>>>> + if (iov_pages + 1 <= vq->num_max) > >>>> > >>>> I think this check is actual only for case one we don't have indirect buffer feature. > >>>> With indirect mode whole data to send will be packed into one indirect buffer. > >>>> > >>>> Thanks, Arseniy > >>> > >>> Actually the reverse. With indirect you are limited to num_max. > >>> Without you are limited to whatever space is left in the > >>> queue (which you did not check here, so you should). > >> > >> I mean that with indirect, we only need one buffer, and we can just wait > >> for enough space - for this single buffer ( as we discussed a little bit before). > >> But if indirect buffer is not supported - we need that whole packet must fit > >> to the size of tx queue - otherwise it never be transmitted. > >> > >> Thanks, Arseniy > > > > > > yes but according to virtio spec it's illegal to add s/g that is bigger > > than queue size. > > Aah, so even in case of indirect buffers feature, buffer descriptors stored in memory > pointed by indirect buffer must be accounted against queue size ? > > Thanks, Arseniya single indirect buffer can't exceed vq size.> > > >>> > >>> > >>>>> + res = true; > >>>>> + } > >>>>> + > >>>>> + rcu_read_unlock(); > >>> > >>> Just curious: > >>> is the point of all this RCU dance to allow vsock > >>> to change from under us? then why is it ok to > >>> have it change? the virtio_transport_msgzerocopy_check_iov > >>> will then refer to the old vsock ... > >>> > >>> > >>>>> + > >>>>> + return res; > >>>>> +} > >>>>> + > >>>>> static bool virtio_transport_seqpacket_allow(u32 remote_cid); > >>>>> > >>>>> static struct virtio_transport virtio_transport = { > >>>>> @@ -475,6 +512,8 @@ static struct virtio_transport virtio_transport = { > >>>>> .seqpacket_allow = virtio_transport_seqpacket_allow, > >>>>> .seqpacket_has_data = virtio_transport_seqpacket_has_data, > >>>>> > >>>>> + .msgzerocopy_check_iov = virtio_transport_msgzerocopy_check_iov, > >>>>> + > >>>>> .notify_poll_in = virtio_transport_notify_poll_in, > >>>>> .notify_poll_out = virtio_transport_notify_poll_out, > >>>>> .notify_recv_init = virtio_transport_notify_recv_init, > >>>>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c > >>>>> index 26a4d10da205..e4e3d541aff4 100644 > >>>>> --- a/net/vmw_vsock/virtio_transport_common.c > >>>>> +++ b/net/vmw_vsock/virtio_transport_common.c > >>>>> @@ -37,73 +37,122 @@ virtio_transport_get_ops(struct vsock_sock *vsk) > >>>>> return container_of(t, struct virtio_transport, transport); > >>>>> } > >>>>> > >>>>> -/* Returns a new packet on success, otherwise returns NULL. > >>>>> - * > >>>>> - * If NULL is returned, errp is set to a negative errno. > >>>>> - */ > >>>>> -static struct sk_buff * > >>>>> -virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info, > >>>>> - size_t len, > >>>>> - u32 src_cid, > >>>>> - u32 src_port, > >>>>> - u32 dst_cid, > >>>>> - u32 dst_port) > >>>>> -{ > >>>>> - const size_t skb_len = VIRTIO_VSOCK_SKB_HEADROOM + len; > >>>>> - struct virtio_vsock_hdr *hdr; > >>>>> - struct sk_buff *skb; > >>>>> - void *payload; > >>>>> - int err; > >>>>> +static bool virtio_transport_can_zcopy(struct virtio_vsock_pkt_info *info, > >>>>> + size_t max_to_send) > >>>>> +{ > >>>>> + const struct vsock_transport *t; > >>>>> + struct iov_iter *iov_iter; > >>>>> > >>>>> - skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL); > >>>>> - if (!skb) > >>>>> - return NULL; > >>>>> + if (!info->msg) > >>>>> + return false; > >>>>> > >>>>> - hdr = virtio_vsock_hdr(skb); > >>>>> - hdr->type = cpu_to_le16(info->type); > >>>>> - hdr->op = cpu_to_le16(info->op); > >>>>> - hdr->src_cid = cpu_to_le64(src_cid); > >>>>> - hdr->dst_cid = cpu_to_le64(dst_cid); > >>>>> - hdr->src_port = cpu_to_le32(src_port); > >>>>> - hdr->dst_port = cpu_to_le32(dst_port); > >>>>> - hdr->flags = cpu_to_le32(info->flags); > >>>>> - hdr->len = cpu_to_le32(len); > >>>>> + iov_iter = &info->msg->msg_iter; > >>>>> > >>>>> - if (info->msg && len > 0) { > >>>>> - payload = skb_put(skb, len); > >>>>> - err = memcpy_from_msg(payload, info->msg, len); > >>>>> - if (err) > >>>>> - goto out; > >>>>> + t = vsock_core_get_transport(info->vsk); > >>>>> > >>>>> - if (msg_data_left(info->msg) == 0 && > >>>>> - info->type == VIRTIO_VSOCK_TYPE_SEQPACKET) { > >>>>> - hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM); > >>>>> + if (t->msgzerocopy_check_iov && > >>>>> + !t->msgzerocopy_check_iov(iov_iter)) > >>>>> + return false; > >>>>> > >>>>> - if (info->msg->msg_flags & MSG_EOR) > >>>>> - hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR); > >>>>> - } > >>>>> + /* Data is simple buffer. */ > >>>>> + if (iter_is_ubuf(iov_iter)) > >>>>> + return true; > >>>>> + > >>>>> + if (!iter_is_iovec(iov_iter)) > >>>>> + return false; > >>>>> + > >>>>> + if (iov_iter->iov_offset) > >>>>> + return false; > >>>>> + > >>>>> + /* We can't send whole iov. */ > >>>>> + if (iov_iter->count > max_to_send) > >>>>> + return false; > >>>>> + > >>>>> + return true; > >>>>> +} > >>>>> + > >>>>> +static int virtio_transport_init_zcopy_skb(struct vsock_sock *vsk, > >>>>> + struct sk_buff *skb, > >>>>> + struct msghdr *msg, > >>>>> + bool zerocopy) > >>>>> +{ > >>>>> + struct ubuf_info *uarg; > >>>>> + > >>>>> + if (msg->msg_ubuf) { > >>>>> + uarg = msg->msg_ubuf; > >>>>> + net_zcopy_get(uarg); > >>>>> + } else { > >>>>> + struct iov_iter *iter = &msg->msg_iter; > >>>>> + struct ubuf_info_msgzc *uarg_zc; > >>>>> + int len; > >>>>> + > >>>>> + /* Only ITER_IOVEC or ITER_UBUF are allowed and > >>>>> + * checked before. > >>>>> + */ > >>>>> + if (iter_is_iovec(iter)) > >>>>> + len = iov_length(iter->__iov, iter->nr_segs); > >>>>> + else > >>>>> + len = iter->count; > >>>>> + > >>>>> + uarg = msg_zerocopy_realloc(sk_vsock(vsk), > >>>>> + len, > >>>>> + NULL); > >>>>> + if (!uarg) > >>>>> + return -1; > >>>>> + > >>>>> + uarg_zc = uarg_to_msgzc(uarg); > >>>>> + uarg_zc->zerocopy = zerocopy ? 1 : 0; > >>>>> } > >>>>> > >>>>> - if (info->reply) > >>>>> - virtio_vsock_skb_set_reply(skb); > >>>>> + skb_zcopy_init(skb, uarg); > >>>>> > >>>>> - trace_virtio_transport_alloc_pkt(src_cid, src_port, > >>>>> - dst_cid, dst_port, > >>>>> - len, > >>>>> - info->type, > >>>>> - info->op, > >>>>> - info->flags); > >>>>> + return 0; > >>>>> +} > >>>>> > >>>>> - if (info->vsk && !skb_set_owner_sk_safe(skb, sk_vsock(info->vsk))) { > >>>>> - WARN_ONCE(1, "failed to allocate skb on vsock socket with sk_refcnt == 0\n"); > >>>>> - goto out; > >>>>> +static int virtio_transport_fill_skb(struct sk_buff *skb, > >>>>> + struct virtio_vsock_pkt_info *info, > >>>>> + size_t len, > >>>>> + bool zcopy) > >>>>> +{ > >>>>> + if (zcopy) { > >>>>> + return __zerocopy_sg_from_iter(info->msg, NULL, skb, > >>>>> + &info->msg->msg_iter, > >>>>> + len); > >>>>> + } else { > >>>>> + void *payload; > >>>>> + int err; > >>>>> + > >>>>> + payload = skb_put(skb, len); > >>>>> + err = memcpy_from_msg(payload, info->msg, len); > >>>>> + if (err) > >>>>> + return -1; > >>>>> + > >>>>> + if (msg_data_left(info->msg)) > >>>>> + return 0; > >>>>> + > >>>>> + return 0; > >>>>> } > >>>>> +} > >>>>> > >>>>> - return skb; > >>>>> +static void virtio_transport_init_hdr(struct sk_buff *skb, > >>>>> + struct virtio_vsock_pkt_info *info, > >>>>> + u32 src_cid, > >>>>> + u32 src_port, > >>>>> + u32 dst_cid, > >>>>> + u32 dst_port, > >>>>> + size_t len) > >>>>> +{ > >>>>> + struct virtio_vsock_hdr *hdr; > >>>>> > >>>>> -out: > >>>>> - kfree_skb(skb); > >>>>> - return NULL; > >>>>> + hdr = virtio_vsock_hdr(skb); > >>>>> + hdr->type = cpu_to_le16(info->type); > >>>>> + hdr->op = cpu_to_le16(info->op); > >>>>> + hdr->src_cid = cpu_to_le64(src_cid); > >>>>> + hdr->dst_cid = cpu_to_le64(dst_cid); > >>>>> + hdr->src_port = cpu_to_le32(src_port); > >>>>> + hdr->dst_port = cpu_to_le32(dst_port); > >>>>> + hdr->flags = cpu_to_le32(info->flags); > >>>>> + hdr->len = cpu_to_le32(len); > >>>>> } > >>>>> > >>>>> static void virtio_transport_copy_nonlinear_skb(const struct sk_buff *skb, > >>>>> @@ -214,6 +263,70 @@ static u16 virtio_transport_get_type(struct sock *sk) > >>>>> return VIRTIO_VSOCK_TYPE_SEQPACKET; > >>>>> } > >>>>> > >>>>> +static struct sk_buff *virtio_transport_alloc_skb(struct vsock_sock *vsk, > >>>>> + struct virtio_vsock_pkt_info *info, > >>>>> + size_t payload_len, > >>>>> + bool zcopy, > >>>>> + u32 src_cid, > >>>>> + u32 src_port, > >>>>> + u32 dst_cid, > >>>>> + u32 dst_port) > >>>>> +{ > >>>>> + struct sk_buff *skb; > >>>>> + size_t skb_len; > >>>>> + > >>>>> + skb_len = VIRTIO_VSOCK_SKB_HEADROOM; > >>>>> + > >>>>> + if (!zcopy) > >>>>> + skb_len += payload_len; > >>>>> + > >>>>> + skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL); > >>>>> + if (!skb) > >>>>> + return NULL; > >>>>> + > >>>>> + virtio_transport_init_hdr(skb, info, src_cid, src_port, > >>>>> + dst_cid, dst_port, > >>>>> + payload_len); > >>>>> + > >>>>> + /* Set owner here, because '__zerocopy_sg_from_iter()' uses > >>>>> + * owner of skb without check to update 'sk_wmem_alloc'. > >>>>> + */ > >>>>> + if (vsk) > >>>>> + skb_set_owner_w(skb, sk_vsock(vsk)); > >>>>> + > >>>>> + if (info->msg && payload_len > 0) { > >>>>> + int err; > >>>>> + > >>>>> + err = virtio_transport_fill_skb(skb, info, payload_len, zcopy); > >>>>> + if (err) > >>>>> + goto out; > >>>>> + > >>>>> + if (info->type == VIRTIO_VSOCK_TYPE_SEQPACKET) { > >>>>> + struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb); > >>>>> + > >>>>> + hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM); > >>>>> + > >>>>> + if (info->msg->msg_flags & MSG_EOR) > >>>>> + hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR); > >>>>> + } > >>>>> + } > >>>>> + > >>>>> + if (info->reply) > >>>>> + virtio_vsock_skb_set_reply(skb); > >>>>> + > >>>>> + trace_virtio_transport_alloc_pkt(src_cid, src_port, > >>>>> + dst_cid, dst_port, > >>>>> + payload_len, > >>>>> + info->type, > >>>>> + info->op, > >>>>> + info->flags); > >>>>> + > >>>>> + return skb; > >>>>> +out: > >>>>> + kfree_skb(skb); > >>>>> + return NULL; > >>>>> +} > >>>>> + > >>>>> /* This function can only be used on connecting/connected sockets, > >>>>> * since a socket assigned to a transport is required. > >>>>> * > >>>>> @@ -222,10 +335,12 @@ static u16 virtio_transport_get_type(struct sock *sk) > >>>>> static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > >>>>> struct virtio_vsock_pkt_info *info) > >>>>> { > >>>>> + u32 max_skb_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE; > >>>>> u32 src_cid, src_port, dst_cid, dst_port; > >>>>> const struct virtio_transport *t_ops; > >>>>> struct virtio_vsock_sock *vvs; > >>>>> u32 pkt_len = info->pkt_len; > >>>>> + bool can_zcopy = false; > >>>>> u32 rest_len; > >>>>> int ret; > >>>>> > >>>>> @@ -254,15 +369,30 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > >>>>> if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW) > >>>>> return pkt_len; > >>>>> > >>>>> + if (info->msg) { > >>>>> + /* If zerocopy is not enabled by 'setsockopt()', we behave as > >>>>> + * there is no MSG_ZEROCOPY flag set. > >>>>> + */ > >>>>> + if (!sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY)) > >>>>> + info->msg->msg_flags &= ~MSG_ZEROCOPY; > >>>>> + > >>>>> + if (info->msg->msg_flags & MSG_ZEROCOPY) > >>>>> + can_zcopy = virtio_transport_can_zcopy(info, pkt_len); > >>>>> + > >>>>> + if (can_zcopy) > >>>>> + max_skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, > >>>>> + (MAX_SKB_FRAGS * PAGE_SIZE)); > >>>>> + } > >>>>> + > >>>>> rest_len = pkt_len; > >>>>> > >>>>> do { > >>>>> struct sk_buff *skb; > >>>>> size_t skb_len; > >>>>> > >>>>> - skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, rest_len); > >>>>> + skb_len = min(max_skb_len, rest_len); > >>>>> > >>>>> - skb = virtio_transport_alloc_skb(info, skb_len, > >>>>> + skb = virtio_transport_alloc_skb(vsk, info, skb_len, can_zcopy, > >>>>> src_cid, src_port, > >>>>> dst_cid, dst_port); > >>>>> if (!skb) { > >>>>> @@ -270,6 +400,17 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > >>>>> break; > >>>>> } > >>>>> > >>>>> + /* This is last skb to send this portion of data. */ > >>>>> + if (info->msg && info->msg->msg_flags & MSG_ZEROCOPY && > >>>>> + skb_len == rest_len && info->op == VIRTIO_VSOCK_OP_RW) { > >>>>> + if (virtio_transport_init_zcopy_skb(vsk, skb, > >>>>> + info->msg, > >>>>> + can_zcopy)) { > >>>>> + ret = -ENOMEM; > >>>>> + break; > >>>>> + } > >>>>> + } > >>>>> + > >>>>> virtio_transport_inc_tx_pkt(vvs, skb); > >>>>> > >>>>> ret = t_ops->send_pkt(skb); > >>>>> @@ -934,7 +1075,7 @@ static int virtio_transport_reset_no_sock(const struct virtio_transport *t, > >>>>> if (!t) > >>>>> return -ENOTCONN; > >>>>> > >>>>> - reply = virtio_transport_alloc_skb(&info, 0, > >>>>> + reply = virtio_transport_alloc_skb(NULL, &info, 0, false, > >>>>> le64_to_cpu(hdr->dst_cid), > >>>>> le32_to_cpu(hdr->dst_port), > >>>>> le64_to_cpu(hdr->src_cid), > >>> > >