On Fri, 1 Aug 2025 13:50:56 -0700 Alex Mastro <amastro@xxxxxx> wrote: > 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 <amastro@xxxxxx> > --- > 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@xxxxxx > 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@xxxxxx > --- > Documentation/filesystems/proc.rst | 14 ++++++++++++++ > drivers/vfio/vfio_main.c | 20 ++++++++++++++++++++ > include/linux/vfio.h | 2 ++ > 3 files changed, 36 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/<pid>/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 <linux/pseudo_fs.h> > #include <linux/rwsem.h> > #include <linux/sched.h> > +#include <linux/seq_file.h> > #include <linux/slab.h> > #include <linux/stat.h> > #include <linux/string.h> > @@ -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) > diff --git a/include/linux/vfio.h b/include/linux/vfio.h > index 707b00772ce1..54076045a44f 100644 > --- a/include/linux/vfio.h > +++ b/include/linux/vfio.h > @@ -16,6 +16,7 @@ > #include <linux/cdev.h> > #include <uapi/linux/vfio.h> > #include <linux/iova_bitmap.h> > +#include <linux/seq_file.h> > > struct kvm; > struct iommufd_ctx; > @@ -135,6 +136,7 @@ struct vfio_device_ops { > void (*dma_unmap)(struct vfio_device *vdev, u64 iova, u64 length); > int (*device_feature)(struct vfio_device *device, u32 flags, > void __user *arg, size_t argsz); > + void (*show_fdinfo)(struct vfio_device *device, struct seq_file *m); > }; Changes in this file look spurious, vfio_device_ops vs vfio_device_fops? Nothing implements or consumes the vfio_device_ops callback here. Thanks, Alex
