Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752122AbdGYVYs (ORCPT ); Tue, 25 Jul 2017 17:24:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:46560 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752211AbdGYVWR (ORCPT ); Tue, 25 Jul 2017 17:22:17 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D22F322BDF 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 03/13] xen/pvcalls: implement socket command and handle events Date: Tue, 25 Jul 2017 14:22:00 -0700 Message-Id: <1501017730-12797-3-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: 4835 Lines: 160 Send a PVCALLS_SOCKET command to the backend, use the masked req_prod_pvt as req_id. This way, req_id is guaranteed to be between 0 and PVCALLS_NR_REQ_PER_RING. We already have a slot in the rsp array ready for the response, and there cannot be two outstanding responses with the same req_id. Wait for the response by waiting on the inflight_req waitqueue and check for the req_id field in rsp[req_id]. Use atomic accesses to read the field. Once a response is received, clear the corresponding rsp slot by setting req_id to PVCALLS_INVALID_ID. Note that PVCALLS_INVALID_ID is invalid only from the frontend point of view. It is not part of the PVCalls protocol. pvcalls_front_event_handler is in charge of copying responses from the ring to the appropriate rsp slot. It is done by copying the body of the response first, then by copying req_id atomically. After the copies, wake up anybody waiting on waitqueue. pvcallss_lock protects accesses to the ring. Signed-off-by: Stefano Stabellini CC: boris.ostrovsky@oracle.com CC: jgross@suse.com --- drivers/xen/pvcalls-front.c | 94 +++++++++++++++++++++++++++++++++++++++++++++ drivers/xen/pvcalls-front.h | 8 ++++ 2 files changed, 102 insertions(+) create mode 100644 drivers/xen/pvcalls-front.h diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c index 5e0b265..d1dbcf1 100644 --- a/drivers/xen/pvcalls-front.c +++ b/drivers/xen/pvcalls-front.c @@ -20,6 +20,8 @@ #include #include +#include "pvcalls-front.h" + #define PVCALLS_INVALID_ID (UINT_MAX) #define RING_ORDER XENBUS_MAX_RING_GRANT_ORDER #define PVCALLS_NR_REQ_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE) @@ -40,9 +42,101 @@ struct pvcalls_bedata { static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id) { + struct xenbus_device *dev = dev_id; + struct pvcalls_bedata *bedata; + struct xen_pvcalls_response *rsp; + uint8_t *src, *dst; + int req_id = 0, more = 0, done = 0; + + if (dev == NULL) + return IRQ_HANDLED; + + bedata = dev_get_drvdata(&dev->dev); + if (bedata == NULL) + return IRQ_HANDLED; + +again: + while (RING_HAS_UNCONSUMED_RESPONSES(&bedata->ring)) { + rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons); + + req_id = rsp->req_id; + src = (uint8_t *)&bedata->rsp[req_id]; + src += sizeof(rsp->req_id); + dst = (uint8_t *)rsp; + dst += sizeof(rsp->req_id); + memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id)); + /* + * First copy the rest of the data, then req_id. It is + * paired with the barrier when accessing bedata->rsp. + */ + smp_wmb(); + WRITE_ONCE(bedata->rsp[req_id].req_id, rsp->req_id); + + done = 1; + bedata->ring.rsp_cons++; + } + + RING_FINAL_CHECK_FOR_RESPONSES(&bedata->ring, more); + if (more) + goto again; + if (done) + wake_up(&bedata->inflight_req); return IRQ_HANDLED; } +int pvcalls_front_socket(struct socket *sock) +{ + struct pvcalls_bedata *bedata; + struct xen_pvcalls_request *req; + int notify, req_id, ret; + + if (!pvcalls_front_dev) + return -EACCES; + /* + * PVCalls only supports domain AF_INET, + * type SOCK_STREAM and protocol 0 sockets for now. + * + * Check socket type here, AF_INET and protocol checks are done + * by the caller. + */ + if (sock->type != SOCK_STREAM) + return -ENOTSUPP; + + bedata = dev_get_drvdata(&pvcalls_front_dev->dev); + + spin_lock(&bedata->pvcallss_lock); + req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1); + if (RING_FULL(&bedata->ring) || + READ_ONCE(bedata->rsp[req_id].req_id) != PVCALLS_INVALID_ID) { + spin_unlock(&bedata->pvcallss_lock); + return -EAGAIN; + } + req = RING_GET_REQUEST(&bedata->ring, req_id); + req->req_id = req_id; + req->cmd = PVCALLS_SOCKET; + req->u.socket.id = (uint64_t) sock; + req->u.socket.domain = AF_INET; + req->u.socket.type = SOCK_STREAM; + req->u.socket.protocol = 0; + + bedata->ring.req_prod_pvt++; + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify); + spin_unlock(&bedata->pvcallss_lock); + if (notify) + notify_remote_via_irq(bedata->irq); + + if (wait_event_interruptible(bedata->inflight_req, + READ_ONCE(bedata->rsp[req_id].req_id) == req_id) != 0) + return -EINTR; + + ret = bedata->rsp[req_id].ret; + /* read ret, then set this rsp slot to be reused */ + smp_mb(); + WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID); + + return ret; +} + static const struct xenbus_device_id pvcalls_front_ids[] = { { "pvcalls" }, { "" } diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h new file mode 100644 index 0000000..b7dabed --- /dev/null +++ b/drivers/xen/pvcalls-front.h @@ -0,0 +1,8 @@ +#ifndef __PVCALLS_FRONT_H__ +#define __PVCALLS_FRONT_H__ + +#include + +int pvcalls_front_socket(struct socket *sock); + +#endif -- 1.9.1