> From: Alex Williamson <[email protected]> > Sent: Friday, April 17, 2026 6:44 AM > > On Wed, 15 Apr 2026 11:14:22 -0700 > Matt Evans <[email protected]> wrote: > > > A DMABUF exports access to BAR resources which need to be requested > > before the DMABUF is handed out. Usually the resources are requested > > when setting up the barmap when the VFIO device fd is mmap()ed, but > > there's no guarantee that's done before a DMABUF is created. > > > > Set up the barmap (and so request resources) in the DMABUF-creation > > path. > > > > Fixes: 5d74781ebc86c ("vfio/pci: Add dma-buf export support for MMIO > regions") > > Signed-off-by: Matt Evans <[email protected]> > > --- > > drivers/vfio/pci/vfio_pci_dmabuf.c | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c > b/drivers/vfio/pci/vfio_pci_dmabuf.c > > index 4ccaf3531e02..fefe7cf4256b 100644 > > --- a/drivers/vfio/pci/vfio_pci_dmabuf.c > > +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c > > @@ -272,6 +272,15 @@ int vfio_pci_core_feature_dma_buf(struct > vfio_pci_core_device *vdev, u32 flags, > > goto err_free_priv; > > } > > > > + /* > > + * See comment in vfio_pci_core_mmap(); ensure PCI regions > > + * were requested before returning DMABUFs that reference > > + * them. Barmap setup does this: > > + */ > > + ret = vfio_pci_core_setup_barmap(vdev, get_dma_buf.region_index); > > + if (ret) > > + goto err_free_phys; > > + > > priv->vdev = vdev; > > priv->nr_ranges = get_dma_buf.nr_ranges; > > priv->size = length; > > Wouldn't this get a lot easier if we just setup all the barmaps in > vfio_pci_core_enable(), conditional on pci_resource_len() just like we > use to filter in REGION_INFO? > > I don't recall if there's some reason we've avoid this so far, maybe > others can shout it out if they do.
I don't remember too. probably just because it's not a wide requirement then was made in this on-demand approach... > > We already tear them all down in vfio_pci_core_disable(). It would be > a small patch to add that, which we would mark as Fixes:, then a small > follow-up on top of that that removes any then redundant or unnecessary > callers (all of them). Thoughts? Thanks, > Agree. then the next patch fixing the racing conditions is also not required.
