[Qemu-devel] [PATCH v4] memory: assert on out of scope notification

[Yan Zhao <yan.y.zhao@intel.com>]

It is wrong for an entry to have parts out of scope of notifier's range.
assert this condition.

Out of scope mapping/unmapping would cause problem, as in below case:

1. initially there are two notifiers with ranges
0-0xfedfffff, 0xfef00000-0xffffffffffffffff,
IOVAs from 0x3c000000 - 0x3c1fffff is in shadow page table.

2. in vfio, memory_region_register_iommu_notifier() is followed by
memory_region_iommu_replay(), which will first call address space
unmap,
and walk and add back all entries in vtd shadow page table. e.g.
(1) for notifier 0-0xfedfffff,
    IOVAs from 0 - 0xffffffff get unmapped,
    and IOVAs from 0x3c000000 - 0x3c1fffff get mapped
(2) for notifier 0xfef00000-0xffffffffffffffff
    IOVAs from 0 - 0x7fffffffff get unmapped,
    but IOVAs from 0x3c000000 - 0x3c1fffff cannot get mapped back.

Cc: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>

---
v4:
1. modified commit title
2. using "assert" instead of printing warning message
(Eric Auger)

v3:
refined code style and message format

v2:
1. added a local variable entry_end (Eric Auger)
2. using PRIx64 as format for address range in warning message
(Eric Auger)
---
 memory.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/memory.c b/memory.c
index 0a089a7..35e8e77 100644
--- a/memory.c
+++ b/memory.c
@@ -1937,16 +1937,18 @@ void memory_region_notify_one(IOMMUNotifier *notifier,
                               IOMMUTLBEntry *entry)
 {
     IOMMUNotifierFlag request_flags;
+    hwaddr entry_end = entry->iova + entry->addr_mask;
 
     /*
      * Skip the notification if the notification does not overlap
      * with registered range.
      */
-    if (notifier->start > entry->iova + entry->addr_mask ||
-        notifier->end < entry->iova) {
+    if (notifier->start > entry_end || notifier->end < entry->iova) {
         return;
     }
 
+    assert(entry->iova >= notifier->start && entry_end <= notifier->end);
+
     if (entry->perm & IOMMU_RW) {
         request_flags = IOMMU_NOTIFIER_MAP;
     } else {
-- 
2.7.4