Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752608AbdGZO2F (ORCPT ); Wed, 26 Jul 2017 10:28:05 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:39941 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751801AbdGZO2D (ORCPT ); Wed, 26 Jul 2017 10:28:03 -0400 Subject: Re: [PATCH v2 03/13] xen/pvcalls: implement socket command and handle events To: Stefano Stabellini , xen-devel@lists.xen.org References: <1501017730-12797-1-git-send-email-sstabellini@kernel.org> <1501017730-12797-3-git-send-email-sstabellini@kernel.org> Cc: linux-kernel@vger.kernel.org, jgross@suse.com, Stefano Stabellini From: Boris Ostrovsky Organization: Oracle Corporation Message-ID: <5978A6E3.7010809@oracle.com> Date: Wed, 26 Jul 2017 10:27:47 -0400 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: <1501017730-12797-3-git-send-email-sstabellini@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5290 Lines: 169 On 7/25/2017 5:22 PM, Stefano Stabellini wrote: > 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); These two lines can be combined (both src and dst) > + 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) "!= 0" can be dropped -boris > + 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