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Thu, 29 Jul 2021 00:49:30 +0000 Received: from BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::d017:af2f:7049:5482]) by BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::d017:af2f:7049:5482%5]) with mapi id 15.20.4373.019; Thu, 29 Jul 2021 00:49:30 +0000 From: Jason Gunthorpe To: David Airlie , Tony Krowiak , Alex Williamson , Christian Borntraeger , Cornelia Huck , Jonathan Corbet , Daniel Vetter , Diana Craciun , dri-devel@lists.freedesktop.org, Eric Auger , Eric Farman , Harald Freudenberger , Vasily Gorbik , Heiko Carstens , intel-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org, Jani Nikula , Jason Herne , Joonas Lahtinen , kvm@vger.kernel.org, Kirti Wankhede , linux-doc@vger.kernel.org, linux-s390@vger.kernel.org, Matthew Rosato , Peter Oberparleiter , Halil Pasic , Rodrigo Vivi , Vineeth Vijayan , Zhi Wang Cc: "Raj, Ashok" , Christoph Hellwig , Leon Romanovsky , Max Gurtovoy , Yishai Hadas , Zhenyu Wang Subject: [PATCH v3 09/14] vfio/pci: Change vfio_pci_try_bus_reset() to use the dev_set Date: Wed, 28 Jul 2021 21:49:18 -0300 Message-Id: <9-v3-6c9e19cc7d44+15613-vfio_reflck_jgg@nvidia.com> In-Reply-To: <0-v3-6c9e19cc7d44+15613-vfio_reflck_jgg@nvidia.com> References: Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: YT1PR01CA0096.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:2d::35) To BL0PR12MB5506.namprd12.prod.outlook.com (2603:10b6:208:1cb::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from mlx.ziepe.ca (206.223.160.26) by YT1PR01CA0096.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:2d::35) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4373.18 via Frontend Transport; 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The dev_set->lock directly prevents devices from joining/leaving the set, which further implies the pci_device cannot change drivers or that the vfio_device be freed, eliminating the need for get/put's. Completeness of the device set can be directly measured by checking if every PCI device in the reset group is also in the device set - which proves that VFIO drivers are attached to everything. This restructuring corrects a call to pci_dev_driver() without holding the device_lock() and removes a hard wiring to &vfio_pci_driver. Signed-off-by: Jason Gunthorpe --- drivers/vfio/pci/vfio_pci.c | 148 +++++++++++++++--------------------- 1 file changed, 62 insertions(+), 86 deletions(-) diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c index 5d6db93d6c680f..a1ae9a83a38621 100644 --- a/drivers/vfio/pci/vfio_pci.c +++ b/drivers/vfio/pci/vfio_pci.c @@ -404,6 +404,9 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) struct vfio_pci_ioeventfd *ioeventfd, *ioeventfd_tmp; int i, bar; + /* For needs_reset */ + lockdep_assert_held(&vdev->vdev.dev_set->lock); + /* Stop the device from further DMA */ pci_clear_master(pdev); @@ -2145,7 +2148,7 @@ static struct pci_driver vfio_pci_driver = { .err_handler = &vfio_err_handlers, }; -static int vfio_pci_get_unused_devs(struct pci_dev *pdev, void *data) +static int vfio_pci_try_zap_and_vma_lock_cb(struct pci_dev *pdev, void *data) { struct vfio_devices *devs = data; struct vfio_device *device; @@ -2165,8 +2168,11 @@ static int vfio_pci_get_unused_devs(struct pci_dev *pdev, void *data) vdev = container_of(device, struct vfio_pci_device, vdev); - /* Fault if the device is not unused */ - if (device->open_count) { + /* + * Locking multiple devices is prone to deadlock, runaway and + * unwind if we hit contention. + */ + if (!vfio_pci_zap_and_vma_lock(vdev, true)) { vfio_device_put(device); return -EBUSY; } @@ -2175,112 +2181,82 @@ static int vfio_pci_get_unused_devs(struct pci_dev *pdev, void *data) return 0; } -static int vfio_pci_try_zap_and_vma_lock_cb(struct pci_dev *pdev, void *data) +static int vfio_pci_is_device_in_set(struct pci_dev *pdev, void *data) { - struct vfio_devices *devs = data; - struct vfio_device *device; - struct vfio_pci_device *vdev; + struct vfio_device_set *dev_set = data; + struct vfio_device *cur; - if (devs->cur_index == devs->max_index) - return -ENOSPC; + lockdep_assert_held(&dev_set->lock); - device = vfio_device_get_from_dev(&pdev->dev); - if (!device) - return -EINVAL; - - if (pci_dev_driver(pdev) != &vfio_pci_driver) { - vfio_device_put(device); - return -EBUSY; - } - - vdev = container_of(device, struct vfio_pci_device, vdev); + list_for_each_entry(cur, &dev_set->device_list, dev_set_list) + if (cur->dev == &pdev->dev) + return 0; + return -EBUSY; +} - /* - * Locking multiple devices is prone to deadlock, runaway and - * unwind if we hit contention. - */ - if (!vfio_pci_zap_and_vma_lock(vdev, true)) { - vfio_device_put(device); - return -EBUSY; +/* + * vfio-core considers a group to be viable and will create a vfio_device even + * if some devices are bound to drivers like pci-stub or pcieport. Here we + * require all PCI devices to be inside our dev_set since that ensures they stay + * put and that every driver controlling the device can co-ordinate with the + * device reset. + */ +static struct pci_dev *vfio_pci_find_reset_target(struct vfio_pci_device *vdev) +{ + struct vfio_device_set *dev_set = vdev->vdev.dev_set; + struct vfio_pci_device *cur; + bool needs_reset = false; + + /* No VFIO device has an open device FD */ + list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) { + if (cur->vdev.open_count) + return NULL; + needs_reset |= cur->needs_reset; } + if (!needs_reset) + return NULL; - devs->devices[devs->cur_index++] = vdev; - return 0; + /* All PCI devices in the group to be reset need to be in our dev_set */ + if (vfio_pci_for_each_slot_or_bus( + vdev->pdev, vfio_pci_is_device_in_set, dev_set, + !pci_probe_reset_slot(vdev->pdev->slot))) + return NULL; + return cur->pdev; } /* * If a bus or slot reset is available for the provided device and: * - All of the devices affected by that bus or slot reset are unused - * (!refcnt) * - At least one of the affected devices is marked dirty via * needs_reset (such as by lack of FLR support) - * Then attempt to perform that bus or slot reset. Callers are required - * to hold vdev->dev_set->lock, protecting the bus/slot reset group from - * concurrent opens. A vfio_device reference is acquired for each device - * to prevent unbinds during the reset operation. - * - * NB: vfio-core considers a group to be viable even if some devices are - * bound to drivers like pci-stub or pcieport. Here we require all devices - * to be bound to vfio_pci since that's the only way we can be sure they - * stay put. + * Then attempt to perform that bus or slot reset. */ static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev) { - struct vfio_devices devs = { .cur_index = 0 }; - int i = 0, ret = -EINVAL; - bool slot = false; - struct vfio_pci_device *tmp; - - if (!pci_probe_reset_slot(vdev->pdev->slot)) - slot = true; - else if (pci_probe_reset_bus(vdev->pdev->bus)) - return; + struct vfio_device_set *dev_set = vdev->vdev.dev_set; + struct pci_dev *to_reset; + struct vfio_pci_device *cur; + int ret; - if (vfio_pci_for_each_slot_or_bus(vdev->pdev, vfio_pci_count_devs, - &i, slot) || !i) - return; + lockdep_assert_held(&vdev->vdev.dev_set->lock); - devs.max_index = i; - devs.devices = kcalloc(i, sizeof(struct vfio_device *), GFP_KERNEL); - if (!devs.devices) + if (pci_probe_reset_slot(vdev->pdev->slot) && + pci_probe_reset_bus(vdev->pdev->bus)) return; - if (vfio_pci_for_each_slot_or_bus(vdev->pdev, - vfio_pci_get_unused_devs, - &devs, slot)) - goto put_devs; - - /* Does at least one need a reset? */ - for (i = 0; i < devs.cur_index; i++) { - tmp = devs.devices[i]; - if (tmp->needs_reset) { - ret = pci_reset_bus(vdev->pdev); - break; - } - } - -put_devs: - for (i = 0; i < devs.cur_index; i++) { - tmp = devs.devices[i]; - - /* - * If reset was successful, affected devices no longer need - * a reset and we should return all the collateral devices - * to low power. If not successful, we either didn't reset - * the bus or timed out waiting for it, so let's not touch - * the power state. - */ - if (!ret) { - tmp->needs_reset = false; + to_reset = vfio_pci_find_reset_target(vdev); + if (!to_reset) + return; - if (tmp != vdev && !disable_idle_d3) - vfio_pci_set_power_state(tmp, PCI_D3hot); - } + ret = pci_reset_bus(to_reset); + if (ret) + return; - vfio_device_put(&tmp->vdev); + list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) { + cur->needs_reset = false; + if (cur->pdev != to_reset && !disable_idle_d3) + vfio_pci_set_power_state(cur, PCI_D3hot); } - - kfree(devs.devices); } static void __exit vfio_pci_cleanup(void) -- 2.32.0