Re: [Intel-gfx] [PATCH v7 8/9] vfio/pci: Extend VFIO_DEVICE_GET_PCI_HOT_RESET_INFO for vfio device cdev

Alex Williamson
2023-06-13T14:32:38Z

On Tue, 13 Jun 2023 12:50:43 +0000
"Liu, Yi L" <yi.l.liu@intel.com> wrote:

> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Tuesday, June 13, 2023 7:47 PM
> >
> > On Fri, Jun 02, 2023 at 05:15:14AM -0700, Yi Liu wrote:
> > > +/*
> > > + * Return devid for a device which is affected by hot-reset.
> > > + * - valid devid > 0 for the device that is bound to the input
> > > + * iommufd_ctx.
> > > + * - devid == VFIO_PCI_DEVID_OWNED for the device that has not
> > > + * been bound to any iommufd_ctx but other device within its
> > > + * group has been bound to the input iommufd_ctx.
> > > + * - devid == VFIO_PCI_DEVID_NOT_OWNED for others. e.g. device
> > > + * is bound to other iommufd_ctx etc.
> > > + */
> > > +int vfio_iommufd_device_hot_reset_devid(struct vfio_device *vdev,
> > > + struct iommufd_ctx *ictx)
> > > +{
> > > + struct iommu_group *group;
> > > + int devid;
> > > +
> > > + if (vfio_iommufd_device_ictx(vdev) == ictx)
> > > + return vfio_iommufd_device_id(vdev);
> > > +
> > > + group = iommu_group_get(vdev->dev);
> > > + if (!group)
> > > + return VFIO_PCI_DEVID_NOT_OWNED;
> > > +
> > > + if (iommufd_ctx_has_group(ictx, group))
> > > + devid = VFIO_PCI_DEVID_OWNED;
> > > + else
> > > + devid = VFIO_PCI_DEVID_NOT_OWNED;
> > > +
> > > + iommu_group_put(group);
> > > +
> > > + return devid;
> > > +}
> > > +EXPORT_SYMBOL_GPL(vfio_iommufd_device_hot_reset_devid);
> >
> > This function really should not be in the core iommufd.c file - it is
> > a purely vfio-pci function - why did you have to place it here?
>
> Put it here can avoid calling iommufd_ctx_has_group() in vfio-pci,
> which requires to import IOMMUFD_NS. If this reason is not so
> strong I can move it back to vfio-pci code.

The PCI-isms here are the name of the function and the return value,
otherwise this is simply a "give me the devid for this device in this
context". The function name is trivial to change and we can define the
internal errno usage such that the vfio-pci-core code can interpret the
correct uAPI value. For example, -EXDEV ("Cross-device link") could
maybe be interpreted as owned and any other errno is not-owned, -ENODEV
maybe being the default.

Errno values are often contentious, are there other suggestions?
Thanks,

Alex