Commit afe4e376 authored by Jason Gunthorpe's avatar Jason Gunthorpe Committed by Alex Williamson
Browse files

vfio: Move IOMMU_CAP_CACHE_COHERENCY test to after we know we have a group 



The test isn't going to work if a group doesn't exist. Normally this isn't
a problem since VFIO isn't going to create a device if there is no group,
but the special CONFIG_VFIO_NOIOMMU behavior allows bypassing this
prevention. The new cap test effectively forces a group and breaks this
config option.

Move the cap test to vfio_group_find_or_alloc() which is the earliest time
we know we have a group available and thus are not running in noiommu mode.

Fixes: e8ae0e14 ("vfio: Require that devices support DMA cache coherence")
Reported-by: default avatarXiang Chen <chenxiang66@hisilicon.com>
Tested-by: default avatarXiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/0-v1-e8934b490f36+f4-vfio_cap_fix_jgg@nvidia.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 88084a3d

drivers/vfio/vfio.c

+10 −7
Original line number Diff line number Diff line
@@ -549,6 +549,16 @@ static struct vfio_group *vfio_group_find_or_alloc(struct device *dev) 
	if (!iommu_group)

		return ERR_PTR(-EINVAL);



	/*

	 * VFIO always sets IOMMU_CACHE because we offer no way for userspace to

	 * restore cache coherency. It has to be checked here because it is only

	 * valid for cases where we are using iommu groups.

	 */

	if (!iommu_capable(dev->bus, IOMMU_CAP_CACHE_COHERENCY)) {

		iommu_group_put(iommu_group);

		return ERR_PTR(-EINVAL);

	}



	group = vfio_group_get_from_iommu(iommu_group);

	if (!group)

		group = vfio_create_group(iommu_group, VFIO_IOMMU);
@@ -601,13 +611,6 @@ static int __vfio_register_dev(struct vfio_device *device, 


int vfio_register_group_dev(struct vfio_device *device)

{

	/*

	 * VFIO always sets IOMMU_CACHE because we offer no way for userspace to

	 * restore cache coherency.

	 */

	if (!iommu_capable(device->dev->bus, IOMMU_CAP_CACHE_COHERENCY))

		return -EINVAL;



	return __vfio_register_dev(device,

		vfio_group_find_or_alloc(device->dev));

}