Re: [RFC PATCH] vfio/type1: Do not support IOMMUs that allow bypass

From: Eric Auger
Date: Fri Oct 16 2015 - 10:03:20 EST


Hi Alex,
On 10/15/2015 10:52 PM, Alex Williamson wrote:
> We can only provide isolation if DMA is forced through the IOMMU
> aperture. Don't allow type1 to be used if this is not the case.
>
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> ---
>
> Eric, I see a number of IOMMU drivers enable this, do the ones you
> care about for ARM set geometry.force_aperture? Thanks,
I am currently using arm-smmu.c. I don't see force_aperture being set.

Best Regards

Eric
>
> Alex
>
> drivers/vfio/vfio_iommu_type1.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 57d8c37..6afa9d4 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -728,6 +728,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
> struct vfio_group *group, *g;
> struct vfio_domain *domain, *d;
> struct bus_type *bus = NULL;
> + struct iommu_domain_geometry geometry;
> int ret;
>
> mutex_lock(&iommu->lock);
> @@ -762,6 +763,17 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
> goto out_free;
> }
>
> + /*
> + * If a domain does not force DMA within the aperture, devices are not
> + * isolated and type1 is not an appropriate IOMMU model.
> + */
> + ret = iommu_domain_get_attr(domain->domain,
> + DOMAIN_ATTR_GEOMETRY, &geometry);
> + if (ret || !geometry.force_aperture) {
> + ret = -EPERM;
> + goto out_domain;
> + }
> +
> if (iommu->nesting) {
> int attr = 1;
>
>

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