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

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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: e8ae0e140c ("vfio: Require that devices support DMA cache coherence")
Reported-by: Xiang Chen <chenxiang66@hisilicon.com>
Tested-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/0-v1-e8934b490f36+f4-vfio_cap_fix_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Jason Gunthorpe 2022-07-04 22:10:50 -03:00 committed by Alex Williamson
parent 88084a3df1
commit afe4e376ac
1 changed files with 10 additions and 7 deletions
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17
drivers/vfio/vfio.c
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@ -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));
}