Print the PCI device name to a vfio device's fdinfo. This enables tools to query which device is associated with a given vfio device fd. It's inspired by eventfd's printing of "eventfd-id" (fs/eventfd.c), which lsof uses to format the NAME column (e.g. "[eventfd:7278]"). This results in output like below: $ cat /proc/"$process_using_vfio"/fdinfo/"$vfio_device_fd" | grep vfio vfio-device-name: 0000:c6:00.0 Signed-off-by: Alex Mastro <amastro@xxxxxx> --- Hello, this is my first patch submission to vfio, and linux. We would like our tools to be able to query the PCI device name for a given vfio-device fd by inspecting a process's open file descriptors. It is inspired by eventfd's id printing, which is nicely formatted by lsof in the NAME column. I am not sure to what extent this should be generalized, so I opted to put as little policy as possible into vfio_main.c, and have each vfio_device_fops implement what it means to show_fdinfo. The only implementer is vfio_pci_ops in this change. Alternatively, if we wanted to normalize show_fdinfo formatting, this could instead hoist the print formatting up into vfio_main.c, and call an optional vfio_device_ops->instance_name() to get the name. I opted not to do this here due to unfamiliarity with other vfio drivers, but am open to changing it. I noticed that other vfio_device_fops are guarded by checks on vfio_device_file.access_granted. From what I can tell, that shouldn't be required here, since a vfio pci device is guaranteed to be able to print its name (due to existence of vfio_device.pdev) after vfio_device_ops.init() construction. This change rooted on the for-linus branch of linux-vfio [1]. [1] https://github.com/awilliam/linux-vfio --- drivers/vfio/pci/vfio_pci.c | 14 ++++++++++++++ drivers/vfio/vfio_main.c | 15 +++++++++++++++ include/linux/vfio.h | 2 ++ 3 files changed, 31 insertions(+) diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c index 5ba39f7623bb..b682766127ab 100644 --- a/drivers/vfio/pci/vfio_pci.c +++ b/drivers/vfio/pci/vfio_pci.c @@ -21,6 +21,7 @@ #include <linux/mutex.h> #include <linux/notifier.h> #include <linux/pm_runtime.h> +#include <linux/seq_file.h> #include <linux/slab.h> #include <linux/types.h> #include <linux/uaccess.h> @@ -125,6 +126,16 @@ static int vfio_pci_open_device(struct vfio_device *core_vdev) return 0; } +#ifdef CONFIG_PROC_FS +static void vfio_pci_core_show_fdinfo(struct vfio_device *core_vdev, struct seq_file *m) +{ + struct vfio_pci_core_device *vdev = + container_of(core_vdev, struct vfio_pci_core_device, vdev); + + seq_printf(m, "vfio-device-name: %s\n", pci_name(vdev->pdev)); +} +#endif + static const struct vfio_device_ops vfio_pci_ops = { .name = "vfio-pci", .init = vfio_pci_core_init_dev, @@ -138,6 +149,9 @@ static const struct vfio_device_ops vfio_pci_ops = { .mmap = vfio_pci_core_mmap, .request = vfio_pci_core_request, .match = vfio_pci_core_match, +#ifdef CONFIG_PROC_FS + .show_fdinfo = vfio_pci_core_show_fdinfo, +#endif .bind_iommufd = vfio_iommufd_physical_bind, .unbind_iommufd = vfio_iommufd_physical_unbind, .attach_ioas = vfio_iommufd_physical_attach_ioas, diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c index 1fd261efc582..e02504247da8 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 +1355,17 @@ 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) +{ + struct vfio_device_file *df = filep->private_data; + struct vfio_device *device = df->device; + + if (device->ops->show_fdinfo) + device->ops->show_fdinfo(device, m); +} +#endif + const struct file_operations vfio_device_fops = { .owner = THIS_MODULE, .open = vfio_device_fops_cdev_open, @@ -1363,6 +1375,9 @@ 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); }; #if IS_ENABLED(CONFIG_IOMMUFD) --- base-commit: c1d9dac0db168198b6f63f460665256dedad9b6e change-id: 20250623-vfio-fdinfo-767e75a1496a Best regards, -- Alex Mastro <amastro@xxxxxx>
