On Thu, 11 Jul 2019 08:18:54 +0200
Eric Auger <eric.au...@redhat.com> wrote:
> We introduce a new IOMMU Memory Region attribute,
> IOMMU_ATTR_VFIO_NESTED that tells whether the virtual IOMMU
> requires HW nested paging for VFIO integration.
>
> Current Intel virtual IOMMU device supports "Caching
> Mode" and does not require 2 stages at physical level to be
> integrated with VFIO. However SMMUv3 does not implement such
> "caching mode" and requires to use HW nested paging.
>
> As such SMMUv3 is the first IOMMU device to advertise this
> attribute.
>
> Signed-off-by: Eric Auger <eric.au...@redhat.com>
> ---
> hw/arm/smmuv3.c | 12 ++++++++++++
> include/exec/memory.h | 3 ++-
> 2 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> index e96d5beb9a..384c02cb91 100644
> --- a/hw/arm/smmuv3.c
> +++ b/hw/arm/smmuv3.c
> @@ -1490,6 +1490,17 @@ static void
> smmuv3_notify_flag_changed(IOMMUMemoryRegion *iommu,
> }
> }
>
> +static int smmuv3_get_attr(IOMMUMemoryRegion *iommu,
> + enum IOMMUMemoryRegionAttr attr,
> + void *data)
> +{
> + if (attr == IOMMU_ATTR_VFIO_NESTED) {
> + *(bool *) data = true;
> + return 0;
> + }
> + return -EINVAL;
> +}
> +
> static void smmuv3_iommu_memory_region_class_init(ObjectClass *klass,
> void *data)
> {
> @@ -1497,6 +1508,7 @@ static void
> smmuv3_iommu_memory_region_class_init(ObjectClass *klass,
>
> imrc->translate = smmuv3_translate;
> imrc->notify_flag_changed = smmuv3_notify_flag_changed;
> + imrc->get_attr = smmuv3_get_attr;
> }
>
> static const TypeInfo smmuv3_type_info = {
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index a078cd033f..e477a630a8 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -204,7 +204,8 @@ struct MemoryRegionOps {
> };
>
> enum IOMMUMemoryRegionAttr {
> - IOMMU_ATTR_SPAPR_TCE_FD
> + IOMMU_ATTR_SPAPR_TCE_FD,
> + IOMMU_ATTR_VFIO_NESTED,
> };
>
> /**
Why VFIO_NESTED vs simply NESTED? I figure any time we need to include
"VFIO" in the descriptions of something, we're probably not describing
the requirement correctly and it just becomes a meaningless tag that
gets ignored outside of VFIO related things. If we're trying to
describe an IOMMU MemoryRegion that supports dynamic faulting rather
than requiring a replay to pre-populate it, then simply define that
semantic rather than hand waving some vfio specific interaction.
Thanks,
Alex
