iommu/virtio: Reject IOMMU page granule larger than PAGE_SIZE

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.

Reported-by: Bharat Bhushan <bbhushan2@marvell.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Bharat Bhushan <bbhushan2@marvell.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20200326093558.2641019-4-jean-philippe@linaro.org
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 9d5d4c94187405f78ff9a402570a997365f55d5f..1adc73d1f90afe8e293202d1bcf8efa2a2503a12 100644 (file)
--- 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;