[Intel-gfx] [PATCH v3 12/12] vfio/pci: Report dev_id in VFIO_DEVICE_GET_PCI_HOT_RESET_INFO

[Alex Williamson]

On Wed, 12 Apr 2023 12:05:50 -0300
Jason Gunthorpe <jgg at nvidia.com> wrote:

> On Wed, Apr 12, 2023 at 07:27:43AM +0000, Tian, Kevin wrote:
> > > From: Jason Gunthorpe
> > > Sent: Wednesday, April 12, 2023 8:01 AM
> > > 
> > > I see this problem as a few basic requirements from a qemu-like
> > > application:
> > > 
> > >  1) Does the configuration I was given support reset right now?
> > >  2) Will the configuration I was given support reset for the duration
> > >     of my execution?
> > >  3) What groups of the devices I already have open does the reset
> > >     effect?
> > >  4) For debugging, report to the user the full list of devices in the
> > >     reset group, in a way that relates back to sysfs.
> > >  5) Away to trigger a reset on a group of devices
> > > 
> > > #1/#2 is the API I suggested here. Ask the kernel if the current
> > > configuration works, and ask it to keep it working.
> > > 
> > > #3 is either INFO and a CAP for BDF or INFO2 reporting dev_id
> > > 
> > > #4 is either INFO and print the BDFs or INFO2 reporting the struct
> > > vfio_device IDR # (eg /sys/class/vfio/vfioXXX/).  
> > 
> > mdev doesn't have BDF. Of course it doesn't support hot_reset either.  
> 
> It should support a reset.. Maybe idxd doesn't, but it should be part
> of the SIOV model. Our SIOV devices would need it for instance.

IIRC we require mdev devices to support VFIO_DEVICE_RESET, hot-reset is
a different beast.  I assume SIOV device support would also require
VFIO_DEVICE_RESET support and hot-reset would also be irrelevant to
them.

> > but it's presented to userspace as a pci device. Is it weird for a pci
> > device which doesn't provide a BDF cap?  
> 
> It is weird for a PCI device, but it is not weird for a VFIO
> device. Leaking the physical labels out of the uAPI is not clean,
> IMHO.
> 
> > from this point the vfio_device IDR# sounds more generic.  
> 
> Yes, I was thinking about this for the SIOV model.

Seems like we're off on a tangent, the hot-reset ioctl is not relevant
to devices simply because they expose a vfio-pci API, there is any
underlying hardware aspect that anything that is only virtualizing a
vfio-pci API shouldn't be concerned with.  Thanks,

Alex