[Qemu-devel] [PATCH] vfio: Use vfio type1 v2 IOMMU interface

[Alex Williamson <alex.williamson@redhat.com>]

The difference between v1 and v2 is fairly subtle, simply more
deterministic behavior for unmaps.  The v1 interface allows the user
to attempt to unmap sub-regions of previous mappings, returning
success with zero size if unable to comply.  This was a reflection of
the underlying IOMMU API.  The v2 interface requires that the user
may only unmap fully contained mappings, ie. an unmap cannot intersect
or bisect a previous mapping, but may cover multiple mappings.  QEMU
never made use of the sub-region v1 support anyway, so we can support
either v1 or v2.  We'll favor v2 since it's newer.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 hw/vfio/common.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index b230ef1..c5d1551 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -662,7 +662,10 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
     container = g_malloc0(sizeof(*container));
     container->space = space;
     container->fd = fd;
-    if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_TYPE1_IOMMU)) {
+    if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_TYPE1_IOMMU) ||
+        ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_TYPE1v2_IOMMU)) {
+        bool v2 = !!ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_TYPE1v2_IOMMU);
+
         ret = ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &fd);
         if (ret) {
             error_report("vfio: failed to set group container: %m");
@@ -670,7 +673,8 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
             goto free_container_exit;
         }
 
-        ret = ioctl(fd, VFIO_SET_IOMMU, VFIO_TYPE1_IOMMU);
+        ret = ioctl(fd, VFIO_SET_IOMMU,
+                    v2 ? VFIO_TYPE1v2_IOMMU : VFIO_TYPE1_IOMMU);
         if (ret) {
             error_report("vfio: failed to set iommu for container: %m");
             ret = -errno;