[Qemu-devel] [PATCH 2/4] vfio: Associate VFIO groups with (guest) IOMMU address spaces

[David Gibson]

The only model so far supported for VFIO passthrough devices is the model
usually used on x86, where all of the guest's RAM is mapped into the
(host) IOMMU and there is no IOMMU visible in the guest.  Later, however
we want to also support guest visible IOMMUs.

In order to do that the vfio subsystem needs to know which address space
its devices are supposed to be in.  In other words the PCI device's
iommu MemoryRegion needs to be passed through to vfio.  This patch updates
the internal interfaces to do that.  So far it doesn't do much with it,
except to verify/enforce that a group is never added to multiple address
spaces.

Signed-off-by: David Gibson <address@hidden>
---
 hw/misc/vfio.c |   38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
index 178dd11..9057964 100644
--- a/hw/misc/vfio.c
+++ b/hw/misc/vfio.c
@@ -116,6 +116,7 @@ enum {
 struct VFIOGroup;
 
 typedef struct VFIOContainer {
+    MemoryRegion *iommu;
     int fd; /* /dev/vfio/vfio, empowered by the attached groups */
     struct {
         /* enable abstraction to support various iommu backends */
@@ -2614,13 +2615,19 @@ static int vfio_load_rom(VFIODevice *vdev)
     return 0;
 }
 
-static int vfio_connect_container(VFIOGroup *group)
+static int vfio_connect_iommu(VFIOGroup *group, MemoryRegion *iommu)
 {
     VFIOContainer *container;
     int ret, fd;
 
     if (group->container) {
-        return 0;
+        if (group->container->iommu == iommu) {
+            return 0;
+        } else {
+            error_report("vfio: group %d used in multiple DMA contexts",
+                         group->groupid);
+            return -EBUSY;
+        }
     }
 
     QLIST_FOREACH(container, &container_list, next) {
@@ -2646,6 +2653,7 @@ static int vfio_connect_container(VFIOGroup *group)
     }
 
     container = g_malloc0(sizeof(*container));
+    container->iommu = iommu;
     container->fd = fd;
 
     if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_TYPE1_IOMMU)) {
@@ -2685,12 +2693,12 @@ static int vfio_connect_container(VFIOGroup *group)
     return 0;
 }
 
-static void vfio_disconnect_container(VFIOGroup *group)
+static void vfio_disconnect_context(VFIOGroup *group)
 {
     VFIOContainer *container = group->container;
 
     if (ioctl(group->fd, VFIO_GROUP_UNSET_CONTAINER, &container->fd)) {
-        error_report("vfio: error disconnecting group %d from container",
+        error_report("vfio: error disconnecting group %d from context",
                      group->groupid);
     }
 
@@ -2702,13 +2710,13 @@ static void vfio_disconnect_container(VFIOGroup *group)
             container->iommu_data.release(container);
         }
         QLIST_REMOVE(container, next);
-        DPRINTF("vfio_disconnect_container: close container->fd\n");
+        DPRINTF("vfio_disconnect_context: close container->fd\n");
         close(container->fd);
         g_free(container);
     }
 }
 
-static VFIOGroup *vfio_get_group(int groupid)
+static VFIOGroup *vfio_get_group(int groupid, MemoryRegion *iommu)
 {
     VFIOGroup *group;
     char path[32];
@@ -2716,7 +2724,15 @@ static VFIOGroup *vfio_get_group(int groupid)
 
     QLIST_FOREACH(group, &group_list, next) {
         if (group->groupid == groupid) {
-            return group;
+            /* Found it.  Now is it already in the right context? */
+            assert(group->container);
+            if (group->container->iommu == iommu) {
+                return group;
+            } else {
+                error_report("vfio: group %d used in multiple DMA contexts",
+                             group->groupid);
+                return NULL;
+            }
         }
     }
 
@@ -2749,8 +2765,8 @@ static VFIOGroup *vfio_get_group(int groupid)
     group->groupid = groupid;
     QLIST_INIT(&group->device_list);
 
-    if (vfio_connect_container(group)) {
-        error_report("vfio: failed to setup container for group %d", groupid);
+    if (vfio_connect_iommu(group, iommu)) {
+        error_report("vfio: failed to setup context for group %d", groupid);
         close(group->fd);
         g_free(group);
         return NULL;
@@ -2767,7 +2783,7 @@ static void vfio_put_group(VFIOGroup *group)
         return;
     }
 
-    vfio_disconnect_container(group);
+    vfio_disconnect_context(group);
     QLIST_REMOVE(group, next);
     DPRINTF("vfio_put_group: close group->fd\n");
     close(group->fd);
@@ -2982,7 +2998,7 @@ static int vfio_initfn(PCIDevice *pdev)
     DPRINTF("%s(%04x:%02x:%02x.%x) group %d\n", __func__, vdev->host.domain,
             vdev->host.bus, vdev->host.slot, vdev->host.function, groupid);
 
-    group = vfio_get_group(groupid);
+    group = vfio_get_group(groupid, pdev->iommu);
     if (!group) {
         error_report("vfio: failed to get group %d", groupid);
         return -ENOENT;
-- 
1.7.10.4