On 2020-03-26 9:35 am, Jean-Philippe Brucker wrote:
We don't currently support IOMMUs with a page granule larger than the
system page size. The IOVA allocator has a BUG_ON() in this case, and
VFIO has a WARN_ON().
Removing these obstacles ranges doesn't seem possible without major
changes to the DMA API and VFIO. Some callers of iommu_map(), for
example, want to map multiple page-aligned regions adjacent to each
others for scatter-gather purposes. Even in simple DMA API uses, a call
to dma_map_page() would let the endpoint access neighbouring memory. And
VFIO users cannot ensure that their virtual address buffer is physically
contiguous at the IOMMU granule.
Rather than triggering the IOVA BUG_ON() on mismatched page sizes, abort
the vdomain finalise() with an error message. We could simply abort the
viommu probe(), but an upcoming extension to virtio-iommu will allow
setting different page masks for each endpoint.
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
Reported-by: Bharat Bhushan <bbhushan2@xxxxxxxxxxx>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
---
v1->v2: Move to vdomain_finalise(), improve commit message
---
drivers/iommu/virtio-iommu.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 5eed75cd121f..750f69c49b95 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -607,12 +607,22 @@ static struct iommu_domain *viommu_domain_alloc(unsigned type)
return &vdomain->domain;
}
-static int viommu_domain_finalise(struct viommu_dev *viommu,
+static int viommu_domain_finalise(struct viommu_endpoint *vdev,
struct iommu_domain *domain)
{
int ret;
+ unsigned long viommu_page_size;
+ struct viommu_dev *viommu = vdev->viommu;
struct viommu_domain *vdomain = to_viommu_domain(domain);
+ viommu_page_size = 1UL << __ffs(viommu->pgsize_bitmap);
+ if (viommu_page_size > PAGE_SIZE) {
+ dev_err(vdev->dev,
+ "granule 0x%lx larger than system page size 0x%lx\n",
+ viommu_page_size, PAGE_SIZE);
+ return -EINVAL;
+ }
+
ret = ida_alloc_range(&viommu->domain_ids, viommu->first_domain,
viommu->last_domain, GFP_KERNEL);
if (ret < 0)
@@ -659,7 +669,7 @@ static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev)
* Properly initialize the domain now that we know which viommu
* owns it.
*/
- ret = viommu_domain_finalise(vdev->viommu, domain);
+ ret = viommu_domain_finalise(vdev, domain);
} else if (vdomain->viommu != vdev->viommu) {
dev_err(dev, "cannot attach to foreign vIOMMU\n");
ret = -EXDEV;
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