From patchwork Thu Mar 16 12:55:20 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yi Liu X-Patchwork-Id: 13177575 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 83E2AC74A5B for ; Thu, 16 Mar 2023 12:55:54 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C6A1F10E1F5; Thu, 16 Mar 2023 12:55:51 +0000 (UTC) Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6397A10E1EB; Thu, 16 Mar 2023 12:55:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1678971349; x=1710507349; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Ac4KtZZ6beubpwmpT9ie22pg4ftKNdsniOLMWnizrzo=; b=NwI27oKkIhNQBU6zSg8WQf0vazjcISvV+nRO1n7GZ/ZVuKXCAzUjv8df Cqu9oWq0zSsQUH2OZtqyOJMDfOvMYcmd3N2DBIwxg1YSjQ0TydzzNhd+t biI3sVO2O1OTodPD/YyDXvuGoXotPdPJ8iKjCvBKEqkAy4XTIdZpEqfcy BEZiUGRfJEf/+mMHcjF3/96e5IuNG4A3aFVDLA5ig3pRdNprGqtx2FN/Z ec9V+lZtheT+atkh75pV3WPbQhSx9VgyQtf0ipMB2kkVdctxZ8uPLdZBh tjpeJCVUdCJVvZNrGXHLBoEIVnjlJtSddIHnBxBEuGK+oBZD7TSXtTFGb g==; X-IronPort-AV: E=McAfee;i="6600,9927,10650"; a="336668081" X-IronPort-AV: E=Sophos;i="5.98,265,1673942400"; d="scan'208";a="336668081" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Mar 2023 05:55:49 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10650"; a="790277803" X-IronPort-AV: E=Sophos;i="5.98,265,1673942400"; d="scan'208";a="790277803" Received: from 984fee00a4c6.jf.intel.com ([10.165.58.231]) by fmsmga002.fm.intel.com with ESMTP; 16 Mar 2023 05:55:48 -0700 From: Yi Liu To: alex.williamson@redhat.com, jgg@nvidia.com, kevin.tian@intel.com Date: Thu, 16 Mar 2023 05:55:20 -0700 Message-Id: <20230316125534.17216-9-yi.l.liu@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230316125534.17216-1-yi.l.liu@intel.com> References: <20230316125534.17216-1-yi.l.liu@intel.com> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH v7 08/22] vfio: Block device access via device fd until device is opened X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-s390@vger.kernel.org, yi.l.liu@intel.com, yi.y.sun@linux.intel.com, mjrosato@linux.ibm.com, kvm@vger.kernel.org, intel-gvt-dev@lists.freedesktop.org, joro@8bytes.org, cohuck@redhat.com, xudong.hao@intel.com, peterx@redhat.com, yan.y.zhao@intel.com, eric.auger@redhat.com, terrence.xu@intel.com, nicolinc@nvidia.com, shameerali.kolothum.thodi@huawei.com, suravee.suthikulpanit@amd.com, intel-gfx@lists.freedesktop.org, chao.p.peng@linux.intel.com, lulu@redhat.com, robin.murphy@arm.com, jasowang@redhat.com Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Allow the vfio_device file to be in a state where the device FD is opened but the device cannot be used by userspace (i.e. its .open_device() hasn't been called). This inbetween state is not used when the device FD is spawned from the group FD, however when we create the device FD directly by opening a cdev it will be opened in the blocked state. The reason for the inbetween state is that userspace only gets a FD but doesn't gain access permission until binding the FD to an iommufd. So in the blocked state, only the bind operation is allowed. Completing bind will allow user to further access the device. This is implemented by adding a flag in struct vfio_device_file to mark the blocked state and using a simple smp_load_acquire() to obtain the flag value and serialize all the device setup with the thread accessing this device. Following this lockless scheme, it can safely handle the device FD unbound->bound but it cannot handle bound->unbound. To allow this we'd need to add a lock on all the vfio ioctls which seems costly. So once device FD is bound, it remains bound until the FD is closed. Suggested-by: Jason Gunthorpe Reviewed-by: Kevin Tian Reviewed-by: Jason Gunthorpe Tested-by: Terrence Xu Tested-by: Nicolin Chen Tested-by: Matthew Rosato Signed-off-by: Yi Liu --- drivers/vfio/group.c | 11 ++++++++++- drivers/vfio/vfio.h | 1 + drivers/vfio/vfio_main.c | 41 ++++++++++++++++++++++++++++++++++------ 3 files changed, 46 insertions(+), 7 deletions(-) diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c index 9a7b2765eef6..4f267ae7bebc 100644 --- a/drivers/vfio/group.c +++ b/drivers/vfio/group.c @@ -194,9 +194,18 @@ static int vfio_device_group_open(struct vfio_device_file *df) df->iommufd = device->group->iommufd; ret = vfio_device_open(df); - if (ret) + if (ret) { df->iommufd = NULL; + goto out_put_kvm; + } + + /* + * Paired with smp_load_acquire() in vfio_device_fops::ioctl/ + * read/write/mmap + */ + smp_store_release(&df->access_granted, true); +out_put_kvm: if (device->open_count == 0) vfio_device_put_kvm(device); diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h index cffc08f5a6f1..854f2c97cb9a 100644 --- a/drivers/vfio/vfio.h +++ b/drivers/vfio/vfio.h @@ -18,6 +18,7 @@ struct vfio_container; struct vfio_device_file { struct vfio_device *device; + bool access_granted; spinlock_t kvm_ref_lock; /* protect kvm field */ struct kvm *kvm; struct iommufd_ctx *iommufd; /* protected by struct vfio_device_set::lock */ diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c index 2ea6cb6d03c7..b515bbda4c74 100644 --- a/drivers/vfio/vfio_main.c +++ b/drivers/vfio/vfio_main.c @@ -1114,6 +1114,10 @@ static long vfio_device_fops_unl_ioctl(struct file *filep, struct vfio_device *device = df->device; int ret; + /* Paired with smp_store_release() following vfio_device_open() */ + if (!smp_load_acquire(&df->access_granted)) + return -EINVAL; + ret = vfio_device_pm_runtime_get(device); if (ret) return ret; @@ -1141,6 +1145,10 @@ static ssize_t vfio_device_fops_read(struct file *filep, char __user *buf, struct vfio_device_file *df = filep->private_data; struct vfio_device *device = df->device; + /* Paired with smp_store_release() following vfio_device_open() */ + if (!smp_load_acquire(&df->access_granted)) + return -EINVAL; + if (unlikely(!device->ops->read)) return -EINVAL; @@ -1154,6 +1162,10 @@ static ssize_t vfio_device_fops_write(struct file *filep, struct vfio_device_file *df = filep->private_data; struct vfio_device *device = df->device; + /* Paired with smp_store_release() following vfio_device_open() */ + if (!smp_load_acquire(&df->access_granted)) + return -EINVAL; + if (unlikely(!device->ops->write)) return -EINVAL; @@ -1165,6 +1177,10 @@ static int vfio_device_fops_mmap(struct file *filep, struct vm_area_struct *vma) struct vfio_device_file *df = filep->private_data; struct vfio_device *device = df->device; + /* Paired with smp_store_release() following vfio_device_open() */ + if (!smp_load_acquire(&df->access_granted)) + return -EINVAL; + if (unlikely(!device->ops->mmap)) return -EINVAL; @@ -1201,6 +1217,24 @@ bool vfio_file_is_valid(struct file *file) } EXPORT_SYMBOL_GPL(vfio_file_is_valid); +/* + * Return true if the input file is a vfio device file and has opened + * the input device. Otherwise, return false. + */ +static bool vfio_file_has_device_access(struct file *file, + struct vfio_device *device) +{ + struct vfio_device *vdev = vfio_device_from_file(file); + struct vfio_device_file *df; + + if (!vdev || vdev != device) + return false; + + df = file->private_data; + + return READ_ONCE(df->access_granted); +} + /** * vfio_file_has_dev - True if the VFIO file is a handle for device * @file: VFIO file to check @@ -1211,17 +1245,12 @@ EXPORT_SYMBOL_GPL(vfio_file_is_valid); bool vfio_file_has_dev(struct file *file, struct vfio_device *device) { struct vfio_group *group; - struct vfio_device *vdev; group = vfio_group_from_file(file); if (group) return vfio_group_has_dev(group, device); - vdev = vfio_device_from_file(file); - if (vdev) - return vdev == device; - - return false; + return vfio_file_has_device_access(file, device); } EXPORT_SYMBOL_GPL(vfio_file_has_dev);