On Fri, 4 Jun 2021 09:13:37 -0300 Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > On Thu, Jun 03, 2021 at 02:41:36PM -0600, Alex Williamson wrote: > > > Could you clarify "vfio_driver"? > > This is the thing providing the vfio_device_ops function pointers. > > So vfio-pci can't know anything about this (although your no-snoop > control probing idea makes sense to me) > > But vfio_mlx5_pci can know > > So can mdev_idxd > > And kvmgt A capability on VFIO_DEVICE_GET_INFO could provide a hint to userspace. Stock vfio-pci could fill it out to the extent advertising if the device is capable of non-coherent DMA based on the Enable No-snoop probing, the device specific vfio_drivers could set it based on knowledge of the device behavior. Another bit might indicate a preference to not suppress non-coherent DMA at the IOMMU. Thanks, Alex
