From patchwork Mon Jun 3 18:56:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Parav Pandit X-Patchwork-Id: 10973891 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3BDC776 for ; Mon, 3 Jun 2019 18:57:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2B1E62868C for ; Mon, 3 Jun 2019 18:57:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1E8FC28688; Mon, 3 Jun 2019 18:57:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 58F3028688 for ; Mon, 3 Jun 2019 18:57:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726603AbfFCS5J (ORCPT ); Mon, 3 Jun 2019 14:57:09 -0400 Received: from mail-il-dmz.mellanox.com ([193.47.165.129]:36533 "EHLO mellanox.co.il" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726055AbfFCS5J (ORCPT ); Mon, 3 Jun 2019 14:57:09 -0400 Received: from Internal Mail-Server by MTLPINE2 (envelope-from parav@mellanox.com) with ESMTPS (AES256-SHA encrypted); 3 Jun 2019 21:57:05 +0300 Received: from sw-mtx-036.mtx.labs.mlnx (sw-mtx-036.mtx.labs.mlnx [10.12.150.149]) by labmailer.mlnx (8.13.8/8.13.8) with ESMTP id x53Iv0Qg018101; Mon, 3 Jun 2019 21:57:03 +0300 From: Parav Pandit To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cohuck@redhat.com, kwankhede@nvidia.com, alex.williamson@redhat.com Cc: cjia@nvidia.com, parav@mellanox.com Subject: [PATCHv6 1/3] vfio/mdev: Improve the create/remove sequence Date: Mon, 3 Jun 2019 13:56:56 -0500 Message-Id: <20190603185658.54517-2-parav@mellanox.com> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20190603185658.54517-1-parav@mellanox.com> References: <20190603185658.54517-1-parav@mellanox.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This patch addresses below two issues and prepares the code to address 3rd issue listed below. 1. mdev device is placed on the mdev bus before it is created in the vendor driver. Once a device is placed on the mdev bus without creating its supporting underlying vendor device, mdev driver's probe() gets triggered. However there isn't a stable mdev available to work on. create_store() mdev_create_device() device_register() ... vfio_mdev_probe() [...] parent->ops->create() vfio_ap_mdev_create() mdev_set_drvdata(mdev, matrix_mdev); /* Valid pointer set above */ Due to this way of initialization, mdev driver who wants to use the mdev, doesn't have a valid mdev to work on. 2. Current creation sequence is, parent->ops_create() groups_register() Remove sequence is, parent->ops->remove() groups_unregister() However, remove sequence should be exact mirror of creation sequence. Once this is achieved, all users of the mdev will be terminated first before removing underlying vendor device. (Follow standard linux driver model). At that point vendor's remove() ops shouldn't fail because taking the device off the bus should terminate any usage. 3. When remove operation fails, mdev sysfs removal attempts to add the file back on already removed device. Following call trace [1] is observed. [1] call trace: kernel: WARNING: CPU: 2 PID: 9348 at fs/sysfs/file.c:327 sysfs_create_file_ns+0x7f/0x90 kernel: CPU: 2 PID: 9348 Comm: bash Kdump: loaded Not tainted 5.1.0-rc6-vdevbus+ #6 kernel: Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b 08/09/2016 kernel: RIP: 0010:sysfs_create_file_ns+0x7f/0x90 kernel: Call Trace: kernel: remove_store+0xdc/0x100 [mdev] kernel: kernfs_fop_write+0x113/0x1a0 kernel: vfs_write+0xad/0x1b0 kernel: ksys_write+0x5a/0xe0 kernel: do_syscall_64+0x5a/0x210 kernel: entry_SYSCALL_64_after_hwframe+0x49/0xbe Therefore, mdev core is improved in following ways. 1. Split the device registration/deregistration sequence so that some things can be done between initialization of the device and hooking it up to the bus respectively after deregistering it from the bus but before giving up our final reference. In particular, this means invoking the ->create() and ->remove() callbacks in those new windows. This gives the vendor driver an initialized mdev device to work with during creation. At the same time, a bus driver who wish to bind to mdev driver also gets initialized mdev device. This follows standard Linux kernel bus and device model. 2. During remove flow, first remove the device from the bus. This ensures that any bus specific devices are removed. Once device is taken off the mdev bus, invoke remove() of mdev from the vendor driver. 3. The driver core device model provides way to register and auto unregister the device sysfs attribute groups at dev->groups. Make use of dev->groups to let core create the groups and eliminate code to avoid explicit groups creation and removal. To ensure, that new sequence is solid, a below stack dump of a process is taken who attempts to remove the device while device is in use by vfio driver and user application. This stack dump validates that vfio driver guards against such device removal when device is in use. cat /proc/21962/stack [<0>] vfio_del_group_dev+0x216/0x3c0 [vfio] [<0>] mdev_remove+0x21/0x40 [mdev] [<0>] device_release_driver_internal+0xe8/0x1b0 [<0>] bus_remove_device+0xf9/0x170 [<0>] device_del+0x168/0x350 [<0>] mdev_device_remove_common+0x1d/0x50 [mdev] [<0>] mdev_device_remove+0x8c/0xd0 [mdev] [<0>] remove_store+0x71/0x90 [mdev] [<0>] kernfs_fop_write+0x113/0x1a0 [<0>] vfs_write+0xad/0x1b0 [<0>] ksys_write+0x5a/0xe0 [<0>] do_syscall_64+0x5a/0x210 [<0>] entry_SYSCALL_64_after_hwframe+0x49/0xbe [<0>] 0xffffffffffffffff This prepares the code to eliminate calling device_create_file() in subsequent patch. Reviewed-by: Cornelia Huck Signed-off-by: Parav Pandit --- drivers/vfio/mdev/mdev_core.c | 94 +++++++++----------------------- drivers/vfio/mdev/mdev_private.h | 2 +- drivers/vfio/mdev/mdev_sysfs.c | 2 +- 3 files changed, 27 insertions(+), 71 deletions(-) diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c index 3cc1a05fde1c..0bef0cae1d4b 100644 --- a/drivers/vfio/mdev/mdev_core.c +++ b/drivers/vfio/mdev/mdev_core.c @@ -102,55 +102,10 @@ static void mdev_put_parent(struct mdev_parent *parent) kref_put(&parent->ref, mdev_release_parent); } -static int mdev_device_create_ops(struct kobject *kobj, - struct mdev_device *mdev) -{ - struct mdev_parent *parent = mdev->parent; - int ret; - - ret = parent->ops->create(kobj, mdev); - if (ret) - return ret; - - ret = sysfs_create_groups(&mdev->dev.kobj, - parent->ops->mdev_attr_groups); - if (ret) - parent->ops->remove(mdev); - - return ret; -} - -/* - * mdev_device_remove_ops gets called from sysfs's 'remove' and when parent - * device is being unregistered from mdev device framework. - * - 'force_remove' is set to 'false' when called from sysfs's 'remove' which - * indicates that if the mdev device is active, used by VMM or userspace - * application, vendor driver could return error then don't remove the device. - * - 'force_remove' is set to 'true' when called from mdev_unregister_device() - * which indicate that parent device is being removed from mdev device - * framework so remove mdev device forcefully. - */ -static int mdev_device_remove_ops(struct mdev_device *mdev, bool force_remove) -{ - struct mdev_parent *parent = mdev->parent; - int ret; - - /* - * Vendor driver can return error if VMM or userspace application is - * using this mdev device. - */ - ret = parent->ops->remove(mdev); - if (ret && !force_remove) - return ret; - - sysfs_remove_groups(&mdev->dev.kobj, parent->ops->mdev_attr_groups); - return 0; -} - static int mdev_device_remove_cb(struct device *dev, void *data) { if (dev_is_mdev(dev)) - mdev_device_remove(dev, true); + mdev_device_remove(dev); return 0; } @@ -310,41 +265,43 @@ int mdev_device_create(struct kobject *kobj, mdev->parent = parent; + device_initialize(&mdev->dev); mdev->dev.parent = dev; mdev->dev.bus = &mdev_bus_type; mdev->dev.release = mdev_device_release; dev_set_name(&mdev->dev, "%pUl", uuid); + mdev->dev.groups = parent->ops->mdev_attr_groups; + mdev->type_kobj = kobj; - ret = device_register(&mdev->dev); - if (ret) { - put_device(&mdev->dev); - goto mdev_fail; - } + ret = parent->ops->create(kobj, mdev); + if (ret) + goto ops_create_fail; - ret = mdev_device_create_ops(kobj, mdev); + ret = device_add(&mdev->dev); if (ret) - goto create_fail; + goto add_fail; ret = mdev_create_sysfs_files(&mdev->dev, type); - if (ret) { - mdev_device_remove_ops(mdev, true); - goto create_fail; - } + if (ret) + goto sysfs_fail; - mdev->type_kobj = kobj; mdev->active = true; dev_dbg(&mdev->dev, "MDEV: created\n"); return 0; -create_fail: - device_unregister(&mdev->dev); +sysfs_fail: + device_del(&mdev->dev); +add_fail: + parent->ops->remove(mdev); +ops_create_fail: + put_device(&mdev->dev); mdev_fail: mdev_put_parent(parent); return ret; } -int mdev_device_remove(struct device *dev, bool force_remove) +int mdev_device_remove(struct device *dev) { struct mdev_device *mdev, *tmp; struct mdev_parent *parent; @@ -373,16 +330,15 @@ int mdev_device_remove(struct device *dev, bool force_remove) mutex_unlock(&mdev_list_lock); type = to_mdev_type(mdev->type_kobj); + mdev_remove_sysfs_files(dev, type); + device_del(&mdev->dev); parent = mdev->parent; + ret = parent->ops->remove(mdev); + if (ret) + dev_err(&mdev->dev, "Remove failed: err=%d\n", ret); - ret = mdev_device_remove_ops(mdev, force_remove); - if (ret) { - mdev->active = true; - return ret; - } - - mdev_remove_sysfs_files(dev, type); - device_unregister(dev); + /* Balances with device_initialize() */ + put_device(&mdev->dev); mdev_put_parent(parent); return 0; diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h index 36cbbdb754de..924ed2274941 100644 --- a/drivers/vfio/mdev/mdev_private.h +++ b/drivers/vfio/mdev/mdev_private.h @@ -60,6 +60,6 @@ void mdev_remove_sysfs_files(struct device *dev, struct mdev_type *type); int mdev_device_create(struct kobject *kobj, struct device *dev, const guid_t *uuid); -int mdev_device_remove(struct device *dev, bool force_remove); +int mdev_device_remove(struct device *dev); #endif /* MDEV_PRIVATE_H */ diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c index cbf94b8165ea..9f774b91d275 100644 --- a/drivers/vfio/mdev/mdev_sysfs.c +++ b/drivers/vfio/mdev/mdev_sysfs.c @@ -236,7 +236,7 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr, if (val && device_remove_file_self(dev, attr)) { int ret; - ret = mdev_device_remove(dev, false); + ret = mdev_device_remove(dev); if (ret) { device_create_file(dev, attr); return ret; From patchwork Mon Jun 3 18:56:57 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Parav Pandit X-Patchwork-Id: 10973889 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5B6221398 for ; Mon, 3 Jun 2019 18:57:25 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4D15828688 for ; Mon, 3 Jun 2019 18:57:25 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 417F8286B2; Mon, 3 Jun 2019 18:57:25 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D6EB828688 for ; Mon, 3 Jun 2019 18:57:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726744AbfFCS5P (ORCPT ); Mon, 3 Jun 2019 14:57:15 -0400 Received: from mail-il-dmz.mellanox.com ([193.47.165.129]:36586 "EHLO mellanox.co.il" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726707AbfFCS5N (ORCPT ); Mon, 3 Jun 2019 14:57:13 -0400 Received: from Internal Mail-Server by MTLPINE2 (envelope-from parav@mellanox.com) with ESMTPS (AES256-SHA encrypted); 3 Jun 2019 21:57:06 +0300 Received: from sw-mtx-036.mtx.labs.mlnx (sw-mtx-036.mtx.labs.mlnx [10.12.150.149]) by labmailer.mlnx (8.13.8/8.13.8) with ESMTP id x53Iv0Qh018101; Mon, 3 Jun 2019 21:57:05 +0300 From: Parav Pandit To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cohuck@redhat.com, kwankhede@nvidia.com, alex.williamson@redhat.com Cc: cjia@nvidia.com, parav@mellanox.com Subject: [PATCHv6 2/3] vfio/mdev: Avoid creating sysfs remove file on stale device removal Date: Mon, 3 Jun 2019 13:56:57 -0500 Message-Id: <20190603185658.54517-3-parav@mellanox.com> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20190603185658.54517-1-parav@mellanox.com> References: <20190603185658.54517-1-parav@mellanox.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If device is removal is initiated by two threads as below, mdev core attempts to create a syfs remove file on stale device. During this flow, below [1] call trace is observed. cpu-0 cpu-1 ----- ----- mdev_unregister_device() device_for_each_child mdev_device_remove_cb mdev_device_remove user_syscall remove_store() mdev_device_remove() [..] unregister device(); /* not found in list or * active=false. */ sysfs_create_file() ..Call trace Now that mdev core follows correct device removal sequence of the linux bus model, remove shouldn't fail in normal cases. If it fails, there is no point of creating a stale file or checking for specific error status. kernel: WARNING: CPU: 2 PID: 9348 at fs/sysfs/file.c:327 sysfs_create_file_ns+0x7f/0x90 kernel: CPU: 2 PID: 9348 Comm: bash Kdump: loaded Not tainted 5.1.0-rc6-vdevbus+ #6 kernel: Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b 08/09/2016 kernel: RIP: 0010:sysfs_create_file_ns+0x7f/0x90 kernel: Call Trace: kernel: remove_store+0xdc/0x100 [mdev] kernel: kernfs_fop_write+0x113/0x1a0 kernel: vfs_write+0xad/0x1b0 kernel: ksys_write+0x5a/0xe0 kernel: do_syscall_64+0x5a/0x210 kernel: entry_SYSCALL_64_after_hwframe+0x49/0xbe Reviewed-by: Cornelia Huck Signed-off-by: Parav Pandit --- drivers/vfio/mdev/mdev_sysfs.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c index 9f774b91d275..ffa3dcebf201 100644 --- a/drivers/vfio/mdev/mdev_sysfs.c +++ b/drivers/vfio/mdev/mdev_sysfs.c @@ -237,10 +237,8 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr, int ret; ret = mdev_device_remove(dev); - if (ret) { - device_create_file(dev, attr); + if (ret) return ret; - } } return count; From patchwork Mon Jun 3 18:56:58 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Parav Pandit X-Patchwork-Id: 10973887 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E654E1398 for ; Mon, 3 Jun 2019 18:57:23 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D6B8F28688 for ; Mon, 3 Jun 2019 18:57:23 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CAB4B286B2; Mon, 3 Jun 2019 18:57:23 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 32B4F28688 for ; Mon, 3 Jun 2019 18:57:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726787AbfFCS5P (ORCPT ); Mon, 3 Jun 2019 14:57:15 -0400 Received: from mail-il-dmz.mellanox.com ([193.47.165.129]:36594 "EHLO mellanox.co.il" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726715AbfFCS5N (ORCPT ); Mon, 3 Jun 2019 14:57:13 -0400 Received: from Internal Mail-Server by MTLPINE2 (envelope-from parav@mellanox.com) with ESMTPS (AES256-SHA encrypted); 3 Jun 2019 21:57:08 +0300 Received: from sw-mtx-036.mtx.labs.mlnx (sw-mtx-036.mtx.labs.mlnx [10.12.150.149]) by labmailer.mlnx (8.13.8/8.13.8) with ESMTP id x53Iv0Qi018101; Mon, 3 Jun 2019 21:57:07 +0300 From: Parav Pandit To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cohuck@redhat.com, kwankhede@nvidia.com, alex.williamson@redhat.com Cc: cjia@nvidia.com, parav@mellanox.com Subject: [PATCHv6 3/3] vfio/mdev: Synchronize device create/remove with parent removal Date: Mon, 3 Jun 2019 13:56:58 -0500 Message-Id: <20190603185658.54517-4-parav@mellanox.com> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20190603185658.54517-1-parav@mellanox.com> References: <20190603185658.54517-1-parav@mellanox.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In following sequences, child devices created while removing mdev parent device can be left out, or it may lead to race of removing half initialized child mdev devices. issue-1: -------- cpu-0 cpu-1 ----- ----- mdev_unregister_device() device_for_each_child() mdev_device_remove_cb() mdev_device_remove() create_store() mdev_device_create() [...] device_add() parent_remove_sysfs_files() /* BUG: device added by cpu-0 * whose parent is getting removed * and it won't process this mdev. */ issue-2: -------- Below crash is observed when user initiated remove is in progress and mdev_unregister_driver() completes parent unregistration. cpu-0 cpu-1 ----- ----- remove_store() mdev_device_remove() active = false; mdev_unregister_device() parent device removed. [...] parents->ops->remove() /* * BUG: Accessing invalid parent. */ This is similar race like create() racing with mdev_unregister_device(). BUG: unable to handle kernel paging request at ffffffffc0585668 PGD e8f618067 P4D e8f618067 PUD e8f61a067 PMD 85adca067 PTE 0 Oops: 0000 [#1] SMP PTI CPU: 41 PID: 37403 Comm: bash Kdump: loaded Not tainted 5.1.0-rc6-vdevbus+ #6 Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b 08/09/2016 RIP: 0010:mdev_device_remove+0xfa/0x140 [mdev] Call Trace: remove_store+0x71/0x90 [mdev] kernfs_fop_write+0x113/0x1a0 vfs_write+0xad/0x1b0 ksys_write+0x5a/0xe0 do_syscall_64+0x5a/0x210 entry_SYSCALL_64_after_hwframe+0x49/0xbe Therefore, mdev core is improved as below to overcome above issues. Wait for any ongoing mdev create() and remove() to finish before unregistering parent device. This continues to allow multiple create and remove to progress in parallel for different mdev devices as most common case. At the same time guard parent removal while parent is being accessed by create() and remove() callbacks. create()/remove() and unregister_device() are synchronized by the rwsem. Refactor device removal code to mdev_device_remove_common() to avoid acquiring unreg_sem of the parent. Fixes: 7b96953bc640 ("vfio: Mediated device Core driver") Signed-off-by: Parav Pandit Reviewed-by: Cornelia Huck --- drivers/vfio/mdev/mdev_core.c | 71 ++++++++++++++++++++++++-------- drivers/vfio/mdev/mdev_private.h | 2 + 2 files changed, 55 insertions(+), 18 deletions(-) diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c index 0bef0cae1d4b..c544656191cd 100644 --- a/drivers/vfio/mdev/mdev_core.c +++ b/drivers/vfio/mdev/mdev_core.c @@ -102,11 +102,35 @@ static void mdev_put_parent(struct mdev_parent *parent) kref_put(&parent->ref, mdev_release_parent); } +/* Caller must hold parent unreg_sem read or write lock */ +static void mdev_device_remove_common(struct mdev_device *mdev) +{ + struct mdev_parent *parent; + struct mdev_type *type; + int ret; + + type = to_mdev_type(mdev->type_kobj); + mdev_remove_sysfs_files(&mdev->dev, type); + device_del(&mdev->dev); + parent = mdev->parent; + lockdep_assert_held(&parent->unreg_sem); + ret = parent->ops->remove(mdev); + if (ret) + dev_err(&mdev->dev, "Remove failed: err=%d\n", ret); + + /* Balances with device_initialize() */ + put_device(&mdev->dev); + mdev_put_parent(parent); +} + static int mdev_device_remove_cb(struct device *dev, void *data) { - if (dev_is_mdev(dev)) - mdev_device_remove(dev); + if (dev_is_mdev(dev)) { + struct mdev_device *mdev; + mdev = to_mdev_device(dev); + mdev_device_remove_common(mdev); + } return 0; } @@ -148,6 +172,7 @@ int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops) } kref_init(&parent->ref); + init_rwsem(&parent->unreg_sem); parent->dev = dev; parent->ops = ops; @@ -206,21 +231,23 @@ void mdev_unregister_device(struct device *dev) dev_info(dev, "MDEV: Unregistering\n"); list_del(&parent->next); + mutex_unlock(&parent_list_lock); + + down_write(&parent->unreg_sem); + class_compat_remove_link(mdev_bus_compat_class, dev, NULL); device_for_each_child(dev, NULL, mdev_device_remove_cb); parent_remove_sysfs_files(parent); + up_write(&parent->unreg_sem); - mutex_unlock(&parent_list_lock); mdev_put_parent(parent); } EXPORT_SYMBOL(mdev_unregister_device); -static void mdev_device_release(struct device *dev) +static void mdev_device_free(struct mdev_device *mdev) { - struct mdev_device *mdev = to_mdev_device(dev); - mutex_lock(&mdev_list_lock); list_del(&mdev->next); mutex_unlock(&mdev_list_lock); @@ -229,6 +256,13 @@ static void mdev_device_release(struct device *dev) kfree(mdev); } +static void mdev_device_release(struct device *dev) +{ + struct mdev_device *mdev = to_mdev_device(dev); + + mdev_device_free(mdev); +} + int mdev_device_create(struct kobject *kobj, struct device *dev, const guid_t *uuid) { @@ -265,6 +299,12 @@ int mdev_device_create(struct kobject *kobj, mdev->parent = parent; + if (!down_read_trylock(&parent->unreg_sem)) { + mdev_device_free(mdev); + ret = -ENODEV; + goto mdev_fail; + } + device_initialize(&mdev->dev); mdev->dev.parent = dev; mdev->dev.bus = &mdev_bus_type; @@ -287,6 +327,7 @@ int mdev_device_create(struct kobject *kobj, mdev->active = true; dev_dbg(&mdev->dev, "MDEV: created\n"); + up_read(&parent->unreg_sem); return 0; @@ -295,6 +336,7 @@ int mdev_device_create(struct kobject *kobj, add_fail: parent->ops->remove(mdev); ops_create_fail: + up_read(&parent->unreg_sem); put_device(&mdev->dev); mdev_fail: mdev_put_parent(parent); @@ -305,8 +347,6 @@ int mdev_device_remove(struct device *dev) { struct mdev_device *mdev, *tmp; struct mdev_parent *parent; - struct mdev_type *type; - int ret; mdev = to_mdev_device(dev); @@ -329,18 +369,13 @@ int mdev_device_remove(struct device *dev) mdev->active = false; mutex_unlock(&mdev_list_lock); - type = to_mdev_type(mdev->type_kobj); - mdev_remove_sysfs_files(dev, type); - device_del(&mdev->dev); parent = mdev->parent; - ret = parent->ops->remove(mdev); - if (ret) - dev_err(&mdev->dev, "Remove failed: err=%d\n", ret); - - /* Balances with device_initialize() */ - put_device(&mdev->dev); - mdev_put_parent(parent); + /* Check if parent unregistration has started */ + if (!down_read_trylock(&parent->unreg_sem)) + return -ENODEV; + mdev_device_remove_common(mdev); + up_read(&parent->unreg_sem); return 0; } diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h index 924ed2274941..398767526276 100644 --- a/drivers/vfio/mdev/mdev_private.h +++ b/drivers/vfio/mdev/mdev_private.h @@ -23,6 +23,8 @@ struct mdev_parent { struct list_head next; struct kset *mdev_types_kset; struct list_head type_list; + /* Synchronize device creation/removal with parent unregistration */ + struct rw_semaphore unreg_sem; }; struct mdev_device {