Hi Jean,
On 3/26/20 10:35 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.
>
> Reported-by: Bharat Bhushan <bbhush...@marvell.com>
> Signed-off-by: Jean-Philippe Brucker <jean-phili...@linaro.org>
Reviewed-by: Eric Auger <eric.au...@redhat.com>
Thanks
Eric
> ---
> 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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