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.
Jason
On Tue, 30 Sep 2025 11:34:08 -0300 Jason Gunthorpe jgg@nvidia.com 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
On Tue, Sep 30, 2025 at 10:52:47AM -0600, Alex Williamson wrote:
On Tue, 30 Sep 2025 11:34:08 -0300 Jason Gunthorpe jgg@nvidia.com 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?
Could work to start! That's a good idea, then we don't have dependencies.
Your proposal would have better granularity, but
Yes, that was my thinking
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.
Small steps..
I added some more commits that remove the userspace buffer and all the duplicated code too.
Jason
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