Re: [PATCH v2 10/10] vfio/pci: Add VFIO_DEVICE_GET_PCI_HOT_RESET_GROUP_INFO

Alex Williamson
2023-03-28T14:26:31Z

On Tue, 28 Mar 2023 06:19:06 +0000
"Tian, Kevin" <kevin.tian@intel.com> wrote:

> > From: Liu, Yi L <yi.l.liu@intel.com>
> > Sent: Tuesday, March 28, 2023 11:32 AM
> >
> > > From: Alex Williamson <alex.williamson@redhat.com>
> > > Sent: Tuesday, March 28, 2023 3:26 AM
> > >
> > > Additionally, VFIO_DEVICE_GET_PCI_HOT_RESET_INFO has a flags arg that
> > > isn't used, why do we need a new ioctl vs defining
> > > VFIO_PCI_HOT_RESET_FLAG_IOMMUFD_DEV_ID.
> >
> > Sure. I can follow this suggestion. BTW. I have a doubt here. This new flag
> > is set by user. What if in the future kernel has new extensions and needs
> > to report something new to the user and add new flags to tell user? Such
> > flag is set by kernel. Then the flags field may have two kinds of flags (some
> > set by user while some set by kernel). Will it mess up the flags space?
> >
>
> flags in a GET_INFO ioctl is for output.
>
> if user needs to use flags as input to select different type of info then it should
> be split into multiple GET_INFO cmds.

I don't know that that's actually a rule, however we don't currently
test flags is zero for input, so in this case I think we are stuck with
it only being for output.

Alternatively, should VFIO_DEVICE_GET_PCI_HOT_RESET_INFO automatically
return the dev_id variant of the output and set a flag to indicate this
is the case when called on a device fd opened as a cdev? Thanks,

Alex