[Qemu-devel] [RFC v4 08/27] hw/vfio/common: Force nested if iommu requires it

[Eric Auger]

In case we detect the address space is translated by
a virtual IOMMU which requires nested stages, let's set up
the container with the VFIO_TYPE1_NESTING_IOMMU iommu_type.

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

---

v2 -> v3:
- add "nested only is selected if requested by @force_nested"
  comment in this patch
---
 hw/vfio/common.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 1f1deff360..99ade21056 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1136,14 +1136,19 @@ static void vfio_put_address_space(VFIOAddressSpace 
*space)
  * vfio_get_iommu_type - selects the richest iommu_type (v2 first)
  */
 static int vfio_get_iommu_type(VFIOContainer *container,
+                               bool force_nested,
                                Error **errp)
 {
-    int iommu_types[] = { VFIO_TYPE1v2_IOMMU, VFIO_TYPE1_IOMMU,
+    int iommu_types[] = { VFIO_TYPE1_NESTING_IOMMU,
+                          VFIO_TYPE1v2_IOMMU, VFIO_TYPE1_IOMMU,
                           VFIO_SPAPR_TCE_v2_IOMMU, VFIO_SPAPR_TCE_IOMMU };
     int i;
 
     for (i = 0; i < ARRAY_SIZE(iommu_types); i++) {
         if (ioctl(container->fd, VFIO_CHECK_EXTENSION, iommu_types[i])) {
+            if (iommu_types[i] == VFIO_TYPE1_NESTING_IOMMU && !force_nested) {
+                continue;
+            }
             return iommu_types[i];
         }
     }
@@ -1152,11 +1157,11 @@ static int vfio_get_iommu_type(VFIOContainer *container,
 }
 
 static int vfio_init_container(VFIOContainer *container, int group_fd,
-                               Error **errp)
+                               bool force_nested, Error **errp)
 {
     int iommu_type, ret;
 
-    iommu_type = vfio_get_iommu_type(container, errp);
+    iommu_type = vfio_get_iommu_type(container, force_nested, errp);
     if (iommu_type < 0) {
         return iommu_type;
     }
@@ -1192,6 +1197,14 @@ static int vfio_connect_container(VFIOGroup *group, 
AddressSpace *as,
     VFIOContainer *container;
     int ret, fd;
     VFIOAddressSpace *space;
+    IOMMUMemoryRegion *iommu_mr;
+    bool force_nested = false;
+
+    if (as != &address_space_memory && memory_region_is_iommu(as->root)) {
+        iommu_mr = IOMMU_MEMORY_REGION(as->root);
+        memory_region_iommu_get_attr(iommu_mr, IOMMU_ATTR_VFIO_NESTED,
+                                     (void *)&force_nested);
+    }
 
     space = vfio_get_address_space(as);
 
@@ -1252,12 +1265,18 @@ static int vfio_connect_container(VFIOGroup *group, 
AddressSpace *as,
     QLIST_INIT(&container->giommu_list);
     QLIST_INIT(&container->hostwin_list);
 
-    ret = vfio_init_container(container, group->fd, errp);
+    ret = vfio_init_container(container, group->fd, force_nested, errp);
     if (ret) {
         goto free_container_exit;
     }
 
+    if (force_nested && container->iommu_type != VFIO_TYPE1_NESTING_IOMMU) {
+            error_setg(errp, "nested mode requested by the virtual IOMMU "
+                       "but not supported by the vfio iommu");
+    }
+
     switch (container->iommu_type) {
+    case VFIO_TYPE1_NESTING_IOMMU:
     case VFIO_TYPE1v2_IOMMU:
     case VFIO_TYPE1_IOMMU:
     {
-- 
2.20.1