[Qemu-devel] [PATCH v4 3/5] hw/vfio/common: Fail on VFIO/HW nested paging detection

[Eric Auger <eric.auger@redhat.com>]

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 guest.

So let's fail on that case.

Signed-off-by: Eric Auger <eric.auger@redhat.com>

---

v3 -> v4:
- use IOMMU_ATTR_HW_NESTED_PAGING
- do not abort anymore but jump to fail
---
 hw/vfio/common.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 3e03c495d8..2b66cf7553 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -606,9 +606,19 @@ 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_HW_NESTED_PAGING,
+                                          (void *)&nested) && nested) {
+            error_report("VFIO/vIOMMU integration based on HW nested paging "
+                         "is not yet supported");
+            ret = -EINVAL;
+            goto fail;
+        }
         /*
          * FIXME: For VFIO iommu types which have KVM acceleration to
          * avoid bouncing all map/unmaps through qemu this way, this
-- 
2.20.1