Re: [Qemu-devel] [PATCH-for-4.2 v3 3/5] hw/vfio/common: Assert in case of nested mode

[Peter Maydell]

On Thu, 11 Jul 2019 at 07:19, Eric Auger <address@hidden> wrote:
>
> As of today, VFIO only works along with vIOMMU supporting
> caching mode. The SMMUv3 does not support this mode and
> requires HW nested paging to work properly with VFIO.
>
> So any attempt to run a VFIO device protected by such IOMMU
> would prevent the assigned device from working and at the
> moment the guest does not even boot as the default
> memory_region_iommu_replay() implementation attempts to
> translate the whole address space and completely stalls
> the execution.
>
> So let's assert if we recognize nested mode case.
>
> Signed-off-by: Eric Auger <address@hidden>
> ---
>  hw/vfio/common.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index a859298fda..d622191fe6 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -604,9 +604,17 @@ static void vfio_listener_region_add(MemoryListener 
> *listener,
>      if (memory_region_is_iommu(section->mr)) {
>          VFIOGuestIOMMU *giommu;
>          IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
> +        bool nested;
>          int iommu_idx;
>
>          trace_vfio_listener_region_add_iommu(iova, end);
> +
> +        if (!memory_region_iommu_get_attr(iommu_mr, IOMMU_ATTR_VFIO_NESTED,
> +                                          (void *)&nested) && nested) {
> +            error_report("VFIO/vIOMMU integration based on HW nested paging "
> +                         "is not yet supported");
> +            abort();
> +        }
>          /*
>           * FIXME: For VFIO iommu types which have KVM acceleration to
>           * avoid bouncing all map/unmaps through qemu this way, this

Other failure paths in this function mostly seem to do an
error_report() and return (apart from the one call to hw_error()
at the bottom of the function). Is an abort() OK here?

thanks
-- PMM