From: Alex Williamson Date: Mon, 15 Jun 2026 19:12:34 +0000 (-0600) Subject: vfio/pci: Expose latched module parameter policy in debugfs X-Git-Tag: v7.2-rc2~21^2~1 X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=586a989d8b0db75d6f97c80a4f588d46e1df6881;p=thirdparty%2Flinux.git vfio/pci: Expose latched module parameter policy in debugfs The nointxmask and disable_idle_d3 module parameters remain writable, but vfio-pci now latches their values into each device at init. Once a device is registered, changing the module parameter only affects future devices, leaving no direct way to confirm the effective policy for an existing device. Add a pci debugfs directory under the VFIO device debugfs root and report the per-device nointxmask and disable_idle_d3 values. These are read-only debugfs views and use the same Y/N bool output convention as the module parameters. Read-only vfio-pci parameters, such as disable_vga, are not exposed here because they cannot drift from the latched device value, therefore the existing module parameter exposure via sysfs is sufficient. Note that while only vfio-pci currently provides these options, the implementation is in vfio-pci-core and therefore properly reflects the device policy in the core, regardless of driver. Assisted-by: OpenAI Codex:gpt-5 Cc: Guixin Liu Signed-off-by: Alex Williamson Reviewed-by: Kevin Tian Link: https://lore.kernel.org/r/20260615191241.688297-7-alex.williamson@nvidia.com Signed-off-by: Alex Williamson --- diff --git a/Documentation/ABI/testing/debugfs-vfio b/Documentation/ABI/testing/debugfs-vfio index 70ec2d454686..ed2f29c3a9b4 100644 --- a/Documentation/ABI/testing/debugfs-vfio +++ b/Documentation/ABI/testing/debugfs-vfio @@ -29,3 +29,29 @@ Date: Oct 2025 KernelVersion: 6.18 Contact: Cédric Le Goater Description: Read the migration features of the vfio device. + +What: /sys/kernel/debug/vfio//pci +Date: June 2026 +KernelVersion: 7.2 +Contact: Alex Williamson +Description: This debugfs file directory is used for debugging + VFIO PCI devices. + +What: /sys/kernel/debug/vfio//pci/nointxmask +Date: June 2026 +KernelVersion: 7.2 +Contact: Alex Williamson +Description: Read the nointxmask policy latched for this device. This + policy governs whether the device may use PCI 2.3 style + INTx masking when supported, reporting a value of "N", or + requires APIC level INTx masking, reporting a value of "Y". + +What: /sys/kernel/debug/vfio//pci/disable_idle_d3 +Date: June 2026 +KernelVersion: 7.2 +Contact: Alex Williamson +Description: Read the disable_idle_d3 policy latched for this device. This + policy governs whether the device PM runtime usage count is + kept elevated while the device is bound to the driver and + unused, reporting a value of "Y", or decremented to allow the + device to enter a low power state, reporting a value of "N". diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index db36d903dcd4..3f11a9624b9c 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -11,6 +11,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include +#include #include #include #include @@ -29,6 +30,7 @@ #include #include #include +#include #if IS_ENABLED(CONFIG_EEH) #include #endif @@ -97,6 +99,60 @@ static inline bool vfio_vga_disabled(struct vfio_pci_core_device *vdev) #endif } +#ifdef CONFIG_VFIO_DEBUGFS +static struct vfio_pci_core_device * +vfio_pci_core_debugfs_private(struct seq_file *seq) +{ + struct device *dev = seq->private; + struct vfio_device *core_vdev = container_of(dev, struct vfio_device, + device); + + return container_of(core_vdev, struct vfio_pci_core_device, vdev); +} + +static int vfio_pci_core_debugfs_nointxmask(struct seq_file *seq, void *data) +{ + struct vfio_pci_core_device *vdev = vfio_pci_core_debugfs_private(seq); + + seq_puts(seq, vdev->nointxmask ? "Y\n" : "N\n"); + return 0; +} + +static int vfio_pci_core_debugfs_disable_idle_d3(struct seq_file *seq, + void *data) +{ + struct vfio_pci_core_device *vdev = vfio_pci_core_debugfs_private(seq); + + seq_puts(seq, vdev->disable_idle_d3 ? "Y\n" : "N\n"); + return 0; +} + +/* + * disable_idle_d3 and nointxmask are writable module parameters latched + * per device at init, so a device's effective value can differ from the + * current parameter setting. Expose the per-device (read-only) values + * here for visibility; read-only parameters can't drift and are omitted. + */ +static void vfio_pci_core_debugfs_init(struct vfio_pci_core_device *vdev) +{ + struct device *dev = &vdev->vdev.device; + struct dentry *pci_dir; + + if (IS_ERR_OR_NULL(vdev->vdev.debug_root)) + return; + + pci_dir = debugfs_create_dir("pci", vdev->vdev.debug_root); + debugfs_create_devm_seqfile(dev, "nointxmask", pci_dir, + vfio_pci_core_debugfs_nointxmask); + debugfs_create_devm_seqfile(dev, "disable_idle_d3", pci_dir, + vfio_pci_core_debugfs_disable_idle_d3); +} +#else +static inline void vfio_pci_core_debugfs_init(struct vfio_pci_core_device *vdev) +{ +} +#endif /* CONFIG_VFIO_DEBUGFS */ + /* * Our VGA arbiter participation is limited since we don't know anything * about the device itself. However, if the device is the only VGA device @@ -2242,6 +2298,9 @@ int vfio_pci_core_register_device(struct vfio_pci_core_device *vdev) ret = vfio_register_group_dev(&vdev->vdev); if (ret) goto out_power; + + vfio_pci_core_debugfs_init(vdev); + return 0; out_power: