Hello Amit,
On 8/7/25 11:34, Amit Machhiwal wrote:
Hello,
On 2025/08/04 12:44 PM, Alex Mastro 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>
I tested this patch on a POWER9 bare metal system with a VFIO PCI device and
could see the VFIO device syspath in fdinfo.
POWER9 running on OPAL FW : I am curious about the software stack.
I suppose this is the latest upstream kernel ?
Are you using an upstream QEMU to test too ?
and which device ?
Thanks,
C.
Without this patch:
-------------------
[root@localhost ~]# cat /proc/7059/fdinfo/188
pos: 0
flags: 02000002
mnt_id: 17
ino: 1113
With this patch:
----------------
[root@localhost ~]# cat /proc/7722/fdinfo/188
pos: 0
flags: 02000002
mnt_id: 17
ino: 2145
vfio-device-syspath: /sys/devices/pci0031:00/0031:00:00.0/0031:01:00.0
..., and the code changes LGTM. Hence,
Reviewed-by: Amit Machhiwal <amachhiw@xxxxxxxxxxxxx>
Tested-by: Amit Machhiwal <amachhiw@xxxxxxxxxxxxx>
Thanks,
Amit
---
Changes in v4:
- Remove changes to vfio.h
- Link to v3: https://lore.kernel.org/r/20250801-show-fdinfo-v3-1-165dfcab89b9@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 ++++++++++++++++++++
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/<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)
---
base-commit: 4518e5a60c7fbf0cdff393c2681db39d77b4f87e
change-id: 20250801-show-fdinfo-ef109ca738cf
Best regards,
--
Alex Mastro <amastro@xxxxxx>
