Print the PCI device syspath to a vfio device's fdinfo. This enables tools to query which device is associated with a given vfio device fd. This results in output like below: $ cat /proc/"$SOME_PID"/fdinfo/"$VFIO_FD" | grep vfio vfio-device-syspath: /sys/devices/pci0000:e0/0000:e0:01.1/0000:e1:00.0/0000:e2:05.0/0000:e8:00.0 Signed-off-by: Alex Mastro --- Changes in v4: - Remove changes to vfio.h - Link to v3: https://lore.kernel.org/r/20250801-show-fdinfo-v3-1-165dfcab89b9@fb.com Changes in v3: - Remove changes to vfio_pci.c - Add section to Documentation/filesystems/proc.rst - Link to v2: https://lore.kernel.org/all/20250724-show-fdinfo-v2-1-2952115edc10@fb.com Changes in v2: - Instead of PCI bdf, print the fully-qualified syspath (prefixed by /sys) to fdinfo. - Rename the field to "vfio-device-syspath". The term "syspath" was chosen for consistency e.g. libudev's usage of the term. - Link to v1: https://lore.kernel.org/r/20250623-vfio-fdinfo-v1-1-c9cec65a2922@fb.com --- Documentation/filesystems/proc.rst | 14 ++++++++++++++ drivers/vfio/vfio_main.c | 20 ++++++++++++++++++++ 2 files changed, 34 insertions(+) diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 2a17865dfe39..fc5ed3117834 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -2162,6 +2162,20 @@ DMA Buffer files where 'size' is the size of the DMA buffer in bytes. 'count' is the file count of the DMA buffer file. 'exp_name' is the name of the DMA buffer exporter. +VFIO Device files +~~~~~~~~~~~~~~~~ + +:: + + pos: 0 + flags: 02000002 + mnt_id: 17 + ino: 5122 + vfio-device-syspath: /sys/devices/pci0000:e0/0000:e0:01.1/0000:e1:00.0/0000:e2:05.0/0000:e8:00.0 + +where 'vfio-device-syspath' is the sysfs path corresponding to the VFIO device +file. + 3.9 /proc//map_files - Information about memory mapped files --------------------------------------------------------------------- This directory contains symbolic links which represent memory mapped files diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c index 1fd261efc582..37a39cee10ed 100644 --- a/drivers/vfio/vfio_main.c +++ b/drivers/vfio/vfio_main.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include #include @@ -1354,6 +1355,22 @@ static int vfio_device_fops_mmap(struct file *filep, struct vm_area_struct *vma) return device->ops->mmap(device, vma); } +#ifdef CONFIG_PROC_FS +static void vfio_device_show_fdinfo(struct seq_file *m, struct file *filep) +{ + char *path; + struct vfio_device_file *df = filep->private_data; + struct vfio_device *device = df->device; + + path = kobject_get_path(&device->dev->kobj, GFP_KERNEL); + if (!path) + return; + + seq_printf(m, "vfio-device-syspath: /sys%s\n", path); + kfree(path); +} +#endif + const struct file_operations vfio_device_fops = { .owner = THIS_MODULE, .open = vfio_device_fops_cdev_open, @@ -1363,6 +1380,9 @@ const struct file_operations vfio_device_fops = { .unlocked_ioctl = vfio_device_fops_unl_ioctl, .compat_ioctl = compat_ptr_ioctl, .mmap = vfio_device_fops_mmap, +#ifdef CONFIG_PROC_FS + .show_fdinfo = vfio_device_show_fdinfo, +#endif }; static struct vfio_device *vfio_device_from_file(struct file *file) --- base-commit: 4518e5a60c7fbf0cdff393c2681db39d77b4f87e change-id: 20250801-show-fdinfo-ef109ca738cf Best regards, -- Alex Mastro