From nobody Fri Nov 7 14:37:10 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1548068782741723.9206983576512; Mon, 21 Jan 2019 03:06:22 -0800 (PST) Received: from localhost ([127.0.0.1]:51875 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1glXPG-0003Pu-Mf for importer@patchew.org; Mon, 21 Jan 2019 06:06:18 -0500 Received: from eggs.gnu.org ([209.51.188.92]:44970) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1glXNj-0002VL-0c for qemu-devel@nongnu.org; Mon, 21 Jan 2019 06:04:44 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1glXNc-0003n6-RY for qemu-devel@nongnu.org; Mon, 21 Jan 2019 06:04:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49666) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1glXNQ-0003ZQ-Ve; Mon, 21 Jan 2019 06:04:28 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6ED6514404F; Mon, 21 Jan 2019 11:04:21 +0000 (UTC) Received: from localhost (ovpn-116-178.ams2.redhat.com [10.36.116.178]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E8AAF104812F; Mon, 21 Jan 2019 11:04:20 +0000 (UTC) From: Cornelia Huck To: Halil Pasic , Eric Farman , Farhan Ali , Pierre Morel Date: Mon, 21 Jan 2019 12:03:51 +0100 Message-Id: <20190121110354.2247-3-cohuck@redhat.com> In-Reply-To: <20190121110354.2247-1-cohuck@redhat.com> References: <20190121110354.2247-1-cohuck@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Mon, 21 Jan 2019 11:04:21 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v2 2/5] vfio-ccw: concurrent I/O handling X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-s390@vger.kernel.org, kvm@vger.kernel.org, Cornelia Huck , Alex Williamson , qemu-devel@nongnu.org, qemu-s390x@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Rework handling of multiple I/O requests to return -EAGAIN if we are already processing an I/O request. Introduce a mutex to disallow concurrent writes to the I/O region. The expectation is that userspace simply retries the operation if it gets -EAGAIN. We currently don't allow multiple ssch requests at the same time, as we don't have support for keeping channel programs around for more than one request. Signed-off-by: Cornelia Huck --- drivers/s390/cio/vfio_ccw_drv.c | 1 + drivers/s390/cio/vfio_ccw_fsm.c | 8 +++----- drivers/s390/cio/vfio_ccw_ops.c | 31 +++++++++++++++++++---------- drivers/s390/cio/vfio_ccw_private.h | 2 ++ 4 files changed, 26 insertions(+), 16 deletions(-) diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_dr= v.c index a10cec0e86eb..2ef189fe45ed 100644 --- a/drivers/s390/cio/vfio_ccw_drv.c +++ b/drivers/s390/cio/vfio_ccw_drv.c @@ -125,6 +125,7 @@ static int vfio_ccw_sch_probe(struct subchannel *sch) =20 private->sch =3D sch; dev_set_drvdata(&sch->dev, private); + mutex_init(&private->io_mutex); =20 spin_lock_irq(sch->lock); private->state =3D VFIO_CCW_STATE_NOT_OPER; diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fs= m.c index cab17865aafe..f6ed934cc565 100644 --- a/drivers/s390/cio/vfio_ccw_fsm.c +++ b/drivers/s390/cio/vfio_ccw_fsm.c @@ -28,7 +28,6 @@ static int fsm_io_helper(struct vfio_ccw_private *private) sch =3D private->sch; =20 spin_lock_irqsave(sch->lock, flags); - private->state =3D VFIO_CCW_STATE_BUSY; =20 orb =3D cp_get_orb(&private->cp, (u32)(addr_t)sch, sch->lpm); =20 @@ -42,6 +41,8 @@ static int fsm_io_helper(struct vfio_ccw_private *private) */ sch->schib.scsw.cmd.actl |=3D SCSW_ACTL_START_PEND; ret =3D 0; + /* Don't allow another ssch for now */ + private->state =3D VFIO_CCW_STATE_BUSY; break; case 1: /* Status pending */ case 2: /* Busy */ @@ -99,7 +100,7 @@ static void fsm_io_error(struct vfio_ccw_private *privat= e, static void fsm_io_busy(struct vfio_ccw_private *private, enum vfio_ccw_event event) { - private->io_region->ret_code =3D -EBUSY; + private->io_region->ret_code =3D -EAGAIN; } =20 static void fsm_disabled_irq(struct vfio_ccw_private *private, @@ -130,8 +131,6 @@ static void fsm_io_request(struct vfio_ccw_private *pri= vate, struct mdev_device *mdev =3D private->mdev; char *errstr =3D "request"; =20 - private->state =3D VFIO_CCW_STATE_BUSY; - memcpy(scsw, io_region->scsw_area, sizeof(*scsw)); =20 if (scsw->cmd.fctl & SCSW_FCTL_START_FUNC) { @@ -176,7 +175,6 @@ static void fsm_io_request(struct vfio_ccw_private *pri= vate, } =20 err_out: - private->state =3D VFIO_CCW_STATE_IDLE; trace_vfio_ccw_io_fctl(scsw->cmd.fctl, get_schid(private), io_region->ret_code, errstr); } diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_op= s.c index f673e106c041..3fa9fc570400 100644 --- a/drivers/s390/cio/vfio_ccw_ops.c +++ b/drivers/s390/cio/vfio_ccw_ops.c @@ -169,16 +169,20 @@ static ssize_t vfio_ccw_mdev_read(struct mdev_device = *mdev, { struct vfio_ccw_private *private; struct ccw_io_region *region; + int ret; =20 if (*ppos + count > sizeof(*region)) return -EINVAL; =20 private =3D dev_get_drvdata(mdev_parent_dev(mdev)); + mutex_lock(&private->io_mutex); region =3D private->io_region; if (copy_to_user(buf, (void *)region + *ppos, count)) - return -EFAULT; - - return count; + ret =3D -EFAULT; + else + ret =3D count; + mutex_unlock(&private->io_mutex); + return ret; } =20 static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev, @@ -188,25 +192,30 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device= *mdev, { struct vfio_ccw_private *private; struct ccw_io_region *region; + int ret; =20 if (*ppos + count > sizeof(*region)) return -EINVAL; =20 private =3D dev_get_drvdata(mdev_parent_dev(mdev)); - if (private->state !=3D VFIO_CCW_STATE_IDLE) + if (private->state =3D=3D VFIO_CCW_STATE_NOT_OPER || + private->state =3D=3D VFIO_CCW_STATE_STANDBY) return -EACCES; + if (!mutex_trylock(&private->io_mutex)) + return -EAGAIN; =20 region =3D private->io_region; - if (copy_from_user((void *)region + *ppos, buf, count)) - return -EFAULT; + if (copy_from_user((void *)region + *ppos, buf, count)) { + ret =3D -EFAULT; + goto out_unlock; + } =20 vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_IO_REQ); - if (region->ret_code !=3D 0) { - private->state =3D VFIO_CCW_STATE_IDLE; - return region->ret_code; - } + ret =3D (region->ret_code !=3D 0) ? region->ret_code : count; =20 - return count; +out_unlock: + mutex_unlock(&private->io_mutex); + return ret; } =20 static int vfio_ccw_mdev_get_device_info(struct vfio_device_info *info) diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_cc= w_private.h index 08e9a7dc9176..e88237697f83 100644 --- a/drivers/s390/cio/vfio_ccw_private.h +++ b/drivers/s390/cio/vfio_ccw_private.h @@ -28,6 +28,7 @@ * @mdev: pointer to the mediated device * @nb: notifier for vfio events * @io_region: MMIO region to input/output I/O arguments/results + * @io_mutex: protect against concurrent update of I/O structures * @cp: channel program for the current I/O operation * @irb: irb info received from interrupt * @scsw: scsw info @@ -42,6 +43,7 @@ struct vfio_ccw_private { struct mdev_device *mdev; struct notifier_block nb; struct ccw_io_region *io_region; + struct mutex io_mutex; =20 struct channel_program cp; struct irb irb; --=20 2.17.2