On 25.07.2023 16:36, Michael S. Tsirkin wrote: > 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@xxxxxxxxxxxxxx> >>>>>>> --- >>>>>>> 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, Arseniy > > a single indirect buffer can't exceed vq size. I see, so i guess right way is to compare length of data "in buffers" again 'num_max', as it is implemented. And we should not refer to whether vq support indirect buffering or not. Thanks, Arseniy > > >>> >>>>> >>>>> >>>>>>> + 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), >>>>> >>> >