[Qemu-devel] [PATCH] vfio: convert to 128 bit arithmetic calculations when adding mem regions

[Bandan Das]

vfio_listener_region_add for a iommu mr results in
an overflow assert since vt-d memory region is initialized
with UINT64_MAX. Convert calculations to 128 bit arithmetic
for such regions and let int128_get64 assert for non iommu
regions only.

Suggested-by: Alex Williamson <address@hidden>
Signed-off-by: Bandan Das <address@hidden>
---
This is v2 of http://patchwork.ozlabs.org/patch/600364/
 hw/vfio/common.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index fb588d8..9489ff3 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -323,7 +323,7 @@ static void vfio_listener_region_add(MemoryListener 
*listener,
 {
     VFIOContainer *container = container_of(listener, VFIOContainer, listener);
     hwaddr iova, end;
-    Int128 llend;
+    Int128 llend, endaddr;
     void *vaddr;
     int ret;
 
@@ -349,14 +349,15 @@ static void vfio_listener_region_add(MemoryListener 
*listener,
     if (int128_ge(int128_make64(iova), llend)) {
         return;
     }
-    end = int128_get64(llend);
+    endaddr = int128_sub(llend, int128_one());
 
-    if ((iova < container->min_iova) || ((end - 1) > container->max_iova)) {
-        error_report("vfio: IOMMU container %p can't map guest IOVA region"
-                     " 0x%"HWADDR_PRIx"..0x%"HWADDR_PRIx,
-                     container, iova, end - 1);
-        ret = -EFAULT;
-        goto fail;
+    if ((iova < container->min_iova) || (int128_get64(endaddr) >
+                                         container->max_iova)) {
+            error_report("vfio: IOMMU container %p can't map guest IOVA region"
+                         " 0x%"HWADDR_PRIx"..0x%"HWADDR_PRIx,
+                         container, iova, int128_get64(endaddr));
+            ret = -EFAULT;
+            goto fail;
     }
 
     memory_region_ref(section->mr);
@@ -364,7 +365,7 @@ static void vfio_listener_region_add(MemoryListener 
*listener,
     if (memory_region_is_iommu(section->mr)) {
         VFIOGuestIOMMU *giommu;
 
-        trace_vfio_listener_region_add_iommu(iova, end - 1);
+        trace_vfio_listener_region_add_iommu(iova, int128_get64(endaddr));
         /*
          * FIXME: We should do some checking to see if the
          * capabilities of the host VFIO IOMMU are adequate to model
@@ -389,6 +390,8 @@ static void vfio_listener_region_add(MemoryListener 
*listener,
         return;
     }
 
+    end = int128_get64(llend);
+
     /* Here we assume that memory_region_is_ram(section->mr)==true */
 
     vaddr = memory_region_get_ram_ptr(section->mr) +
-- 
2.5.0