On Tue, 30 Sep 2025 11:34:08 -0300 Jason Gunthorpe <[email protected]> wrote:
> On Tue, Sep 30, 2025 at 12:50:47PM +0000, Shameer Kolothum wrote: > > > This is where hisi_acc reports a different BAR size as it tries to hide > > the migration control region from Guest access. > > I think for now we should disable DMABUF for any PCI driver that > implements a VFIO_DEVICE_GET_REGION_INFO > > For a while I've wanted to further reduce the use of the ioctl > multiplexer, so maybe this series: > > https://github.com/jgunthorpe/linux/commits/vfio_get_region_info_op/ > > And then the dmabuf code can check if the ops are set to the generic > or not and disable itself automatically. > > Otherwise perhaps route the dmabuf through an op and deliberately omit > it (with a comment!) from hisi, virtio, nvgrace. > > We need to route it through an op anyhow as those three drivers will > probably eventually want to implement their own version. Can't we basically achieve the same by testing the ioctl is vfio_pci_core_ioctl? Your proposal would have better granularity, but we'd probably want an ops callback that we can use without a userspace buffer to get the advertised region size if we ever want to support a device that both modifies the size of the region relative to the BAR and supports p2p. Thanks, Alex
