Re: [PATCH v4] vfio/pci: print vfio-device syspath to fdinfo

[Amit Machhiwal <amachhiw@linux.ibm.com>]

On 2025/08/08 06:44 PM, Cédric Le Goater wrote:
> On 8/8/25 17:45, Amit Machhiwal wrote:
> > Hi Cédric,
> > 
> > Please find my comments inline:
> > 
> > On 2025/08/08 03:49 PM, Cédric Le Goater wrote:
> > > 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@fb.com>
> > > > 
> > > > 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 ?
> > 
> > Yes, I used the latest upstream kernel and applied this patch on top of commit
> > cca7a0aae895.
> > 
> > > Are you using an upstream QEMU to test too ?
> > 
> > No, I had used the Fedora 42 distro qemu. The version details are as below:
> > 
> >    [root@localhost ~]# qemu-system-ppc64 --version
> >    QEMU emulator version 9.2.4 (qemu-9.2.4-1.fc42)
> >    Copyright (c) 2003-2024 Fabrice Bellard and the QEMU Project developers
> > 
> > I gave the upstream qemu (HEAD pointing to cd21ee5b27) a try and I see the same
> > behavior with that too.
> > 
> >    [root@localhost ~]# ./qemu-system-ppc64 --version
> >    QEMU emulator version 10.0.92 (v10.1.0-rc2-4-gcd21ee5b27-dirty)
> >    Copyright (c) 2003-2025 Fabrice Bellard and the QEMU Project developers
> > 
> >    [root@localhost ~]# cat /proc/52807/fdinfo/191
> >    pos:    0
> >    flags:  02000002
> >    mnt_id: 17
> >    ino:    1125
> >    vfio-device-syspath: /sys/devices/pci0031:00/0031:00:00.0/0031:01:00.0
> > 
> > > 
> > > and which device ?
> > 
> > I'm using a Broadcom NetXtreme network card (4-port) and passing through its
> > fn0.
> > 
> >    [root@guest ~]# lspci
> >    [...]
> >    0001:00:01.0 Ethernet controller: Broadcom Inc. and subsidiaries NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
> > 
> > Please let me know if I may help you with any additional information.
> 
> It is good to know that device pass-through still works with upstream on
> OpenPower servers.
> 
> Have you tried VFs ?

I didn't get a chance to try VFs yet, Cédric.

> 
> Thanks Amit,

No problem. :)

Thanks,
Amit

> 
> C.
>