Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752335AbdGYVXf (ORCPT ); Tue, 25 Jul 2017 17:23:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:46578 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752069AbdGYVWT (ORCPT ); Tue, 25 Jul 2017 17:22:19 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3531122C8F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=sstabellini@kernel.org From: Stefano Stabellini To: xen-devel@lists.xen.org Cc: linux-kernel@vger.kernel.org, sstabellini@kernel.org, jgross@suse.com, boris.ostrovsky@oracle.com, Stefano Stabellini Subject: [PATCH v2 09/13] xen/pvcalls: implement recvmsg Date: Tue, 25 Jul 2017 14:22:06 -0700 Message-Id: <1501017730-12797-9-git-send-email-sstabellini@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1501017730-12797-1-git-send-email-sstabellini@kernel.org> References: <1501017730-12797-1-git-send-email-sstabellini@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4603 Lines: 157 Implement recvmsg by copying data from the "in" ring. If not enough data is available and the recvmsg call is blocking, then wait on the inflight_conn_req waitqueue. Take the active socket in_mutex so that only one function can access the ring at any given time. If not enough data is available on the ring, rather than returning immediately or sleep-waiting, spin for up to 5000 cycles. This small optimization turns out to improve performance and latency significantly. Signed-off-by: Stefano Stabellini CC: boris.ostrovsky@oracle.com CC: jgross@suse.com --- drivers/xen/pvcalls-front.c | 106 ++++++++++++++++++++++++++++++++++++++++++++ drivers/xen/pvcalls-front.h | 4 ++ 2 files changed, 110 insertions(+) diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c index d8ed280..b4ca569 100644 --- a/drivers/xen/pvcalls-front.c +++ b/drivers/xen/pvcalls-front.c @@ -96,6 +96,20 @@ static int pvcalls_front_write_todo(struct sock_mapping *map) return size - pvcalls_queued(prod, cons, size); } +static bool pvcalls_front_read_todo(struct sock_mapping *map) +{ + struct pvcalls_data_intf *intf = map->active.ring; + RING_IDX cons, prod; + int32_t error; + + cons = intf->in_cons; + prod = intf->in_prod; + error = intf->in_error; + return (error != 0 || + pvcalls_queued(prod, cons, + XEN_FLEX_RING_SIZE(intf->ring_order))) != 0; +} + static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id) { struct xenbus_device *dev = dev_id; @@ -418,6 +432,98 @@ int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg, return tot_sent; } +static int __read_ring(struct pvcalls_data_intf *intf, + struct pvcalls_data *data, + struct iov_iter *msg_iter, + size_t len, int flags) +{ + RING_IDX cons, prod, size, masked_prod, masked_cons; + RING_IDX array_size = XEN_FLEX_RING_SIZE(intf->ring_order); + int32_t error; + + cons = intf->in_cons; + prod = intf->in_prod; + error = intf->in_error; + /* get pointers before reading from the ring */ + virt_rmb(); + if (error < 0) + return error; + + size = pvcalls_queued(prod, cons, array_size); + masked_prod = pvcalls_mask(prod, array_size); + masked_cons = pvcalls_mask(cons, array_size); + + if (size == 0) + return 0; + + if (len > size) + len = size; + + if (masked_prod > masked_cons) { + copy_to_iter(data->in + masked_cons, len, msg_iter); + } else { + if (len > (array_size - masked_cons)) { + copy_to_iter(data->in + masked_cons, + array_size - masked_cons, msg_iter); + copy_to_iter(data->in, + len - (array_size - masked_cons), + msg_iter); + } else { + copy_to_iter(data->in + masked_cons, len, msg_iter); + } + } + /* read data from the ring before increasing the index */ + virt_mb(); + if (!(flags & MSG_PEEK)) + intf->in_cons += len; + + return len; +} + +int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, + int flags) +{ + struct pvcalls_bedata *bedata; + int ret = -EAGAIN; + struct sock_mapping *map; + int count = 0; + + if (!pvcalls_front_dev) + return -ENOTCONN; + bedata = dev_get_drvdata(&pvcalls_front_dev->dev); + + map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head); + if (!map) + return -ENOTSOCK; + + if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC)) + return -EOPNOTSUPP; + + mutex_lock(&map->active.in_mutex); + if (len > XEN_FLEX_RING_SIZE(map->active.ring->ring_order)) + len = XEN_FLEX_RING_SIZE(map->active.ring->ring_order); + + while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) { + if (count < PVCALLS_FRONT_MAX_SPIN) + count++; + else + wait_event_interruptible(map->active.inflight_conn_req, + pvcalls_front_read_todo(map)); + } + ret = __read_ring(map->active.ring, &map->active.data, + &msg->msg_iter, len, flags); + + if (ret > 0) + notify_remote_via_irq(map->active.irq); + if (ret == 0) + ret = -EAGAIN; + if (ret == -ENOTCONN) + ret = 0; + + mutex_unlock(&map->active.in_mutex); + return ret; +} + int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len) { struct pvcalls_bedata *bedata; diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h index d937c24..de24041 100644 --- a/drivers/xen/pvcalls-front.h +++ b/drivers/xen/pvcalls-front.h @@ -16,5 +16,9 @@ int pvcalls_front_accept(struct socket *sock, int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg, size_t len); +int pvcalls_front_recvmsg(struct socket *sock, + struct msghdr *msg, + size_t len, + int flags); #endif -- 1.9.1