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Tue, 29 Sep 2026 10:33:24 -0700 From: Shameer Kolothum To: , , CC: , , , , , , , , , , Subject: [RFC PATCH v2 01/16] vfio/pci: Add a device access gate Date: Tue, 29 Sep 2026 18:32:50 +0100 Message-ID: <20260929173305.204856-2-skolothumtho@nvidia.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260929173305.204856-1-skolothumtho@nvidia.com> References: <20260929173305.204856-1-skolothumtho@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: rnnvmail203.nvidia.com (10.129.68.9) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BY1PEPF000264B3:EE_|IA3PR12MB460542:EE_ X-MS-Office365-Filtering-Correlation-Id: 8b95ad7a-bfb5-4a10-54e5-08df1e4fd75a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|1800799024|36860700016|82310400026|376014|260925021911599003|11063799006|56012099006|260925021311599003|260925022911599003|10067099003|22082099003|18002099003; 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Add an SRCU-based access gate, enabled by pci_recovery_supported. Serialize open and close state updates with access_lock. Assisted-by: LLM Signed-off-by: Shameer Kolothum --- drivers/vfio/pci/vfio_pci_priv.h | 3 ++ include/linux/vfio_pci_core.h | 19 ++++++++++++ drivers/vfio/pci/vfio_pci_core.c | 53 ++++++++++++++++++++++++++++++++ 3 files changed, 75 insertions(+) diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h index 4e7162234a2e..623e73f379cc 100644 --- a/drivers/vfio/pci/vfio_pci_priv.h +++ b/drivers/vfio/pci/vfio_pci_priv.h @@ -73,6 +73,9 @@ u16 vfio_pci_memory_lock_and_enable(struct vfio_pci_core_device *vdev); void vfio_pci_memory_unlock_and_restore(struct vfio_pci_core_device *vdev, u16 cmd); +int vfio_pci_core_access_begin(struct vfio_pci_core_device *vdev); +void vfio_pci_core_access_end(struct vfio_pci_core_device *vdev, int idx); + #ifdef CONFIG_VFIO_PCI_IGD bool vfio_pci_is_intel_display(struct pci_dev *pdev); int vfio_pci_igd_init(struct vfio_pci_core_device *vdev); diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h index 9a1674c152aa..de0993280344 100644 --- a/include/linux/vfio_pci_core.h +++ b/include/linux/vfio_pci_core.h @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -129,6 +130,7 @@ struct vfio_pci_core_device { bool disable_idle_d3:1; bool nointxmask:1; bool disable_vga:1; + bool pci_recovery_supported:1; /* Flags modified at runtime - dedicated storage unit */ bool needs_reset; bool pm_intx_masked; @@ -148,6 +150,23 @@ struct vfio_pci_core_device { struct vfio_pci_core_device *sriov_pf_core_dev; struct notifier_block nb; struct rw_semaphore memory_lock; + /* + * Device accesses take access_srcu and check device_open and + * access_blocked. To block access, set access_blocked and wait for + * existing readers with synchronize_srcu(). New accesses fail with + * -EIO while blocked. + * + * Close clears access_blocked before device_open. + * + * INTx paths use irqlock instead of access_srcu to coordinate with + * recovery. They read pci_recovery_enabled and access_blocked with + * READ_ONCE(), since writers do not always hold irqlock. + */ + struct srcu_struct access_srcu; + bool access_blocked; + /* Set after open completes, cleared before close tears down state. */ + bool device_open; + struct mutex access_lock; /* gate flag writers */ struct list_head dmabufs; }; diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 6757054e9d87..88a78766c178 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -662,10 +662,18 @@ int vfio_pci_core_enable(struct vfio_pci_core_device *vdev) if (!vfio_vga_disabled(vdev) && vfio_pci_is_vga(pdev)) vdev->has_vga = true; + if (vdev->pci_recovery_supported) { + ret = init_srcu_struct(&vdev->access_srcu); + if (ret) + goto out_free_config; + } + vfio_pci_core_map_bars(vdev); return 0; +out_free_config: + vfio_config_free(vdev); out_free_zdev: vfio_pci_zdev_close_device(vdev); out_free_state: @@ -812,6 +820,9 @@ void vfio_pci_core_disable(struct vfio_pci_core_device *vdev) /* Put the pm-runtime usage counter acquired during enable */ if (!vdev->disable_idle_d3) pm_runtime_put(&pdev->dev); + + if (vdev->pci_recovery_supported) + cleanup_srcu_struct(&vdev->access_srcu); } EXPORT_SYMBOL_GPL(vfio_pci_core_disable); @@ -820,6 +831,13 @@ void vfio_pci_core_close_device(struct vfio_device *core_vdev) struct vfio_pci_core_device *vdev = container_of(core_vdev, struct vfio_pci_core_device, vdev); + if (vdev->pci_recovery_supported) { + scoped_guard(mutex, &vdev->access_lock) { + WRITE_ONCE(vdev->access_blocked, false); + WRITE_ONCE(vdev->device_open, false); + } + } + if (vdev->sriov_pf_core_dev) { mutex_lock(&vdev->sriov_pf_core_dev->vf_token->lock); WARN_ON(!vdev->sriov_pf_core_dev->vf_token->users); @@ -852,6 +870,12 @@ void vfio_pci_core_finish_enable(struct vfio_pci_core_device *vdev) vdev->sriov_pf_core_dev->vf_token->users++; mutex_unlock(&vdev->sriov_pf_core_dev->vf_token->lock); } + + if (vdev->pci_recovery_supported) { + guard(mutex)(&vdev->access_lock); + WRITE_ONCE(vdev->access_blocked, false); + WRITE_ONCE(vdev->device_open, true); + } } EXPORT_SYMBOL_GPL(vfio_pci_core_finish_enable); @@ -1680,6 +1704,33 @@ static ssize_t vfio_pci_rw(struct vfio_pci_core_device *vdev, char __user *buf, return ret; } +/* + * Return an SRCU index for access_end(), or -EIO if access is blocked + * or the device is closed. Do not wait for recovery. + */ +int vfio_pci_core_access_begin(struct vfio_pci_core_device *vdev) +{ + int idx; + + if (!vdev->pci_recovery_supported) + return 0; + + idx = srcu_read_lock(&vdev->access_srcu); + if (unlikely(!READ_ONCE(vdev->device_open) || + READ_ONCE(vdev->access_blocked))) { + srcu_read_unlock(&vdev->access_srcu, idx); + return -EIO; + } + + return idx; +} + +void vfio_pci_core_access_end(struct vfio_pci_core_device *vdev, int idx) +{ + if (vdev->pci_recovery_supported) + srcu_read_unlock(&vdev->access_srcu, idx); +} + ssize_t vfio_pci_core_read(struct vfio_device *core_vdev, char __user *buf, size_t count, loff_t *ppos) { @@ -2196,6 +2247,7 @@ int vfio_pci_core_init_dev(struct vfio_device *core_vdev) if (ret && ret != -EOPNOTSUPP) return ret; INIT_LIST_HEAD(&vdev->dmabufs); + mutex_init(&vdev->access_lock); init_rwsem(&vdev->memory_lock); xa_init(&vdev->ctx); @@ -2210,6 +2262,7 @@ void vfio_pci_core_release_dev(struct vfio_device *core_vdev) mutex_destroy(&vdev->igate); mutex_destroy(&vdev->ioeventfds_lock); + mutex_destroy(&vdev->access_lock); kfree(vdev->region); kfree(vdev->pm_save); } -- 2.43.0