[Qemu-devel] [PATCH] memory: do not do out of bound notification

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

even if an entry overlaps with notifier's range, should not map/unmap
out of bound part in the entry.

This would cause problem 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.

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
---
 memory.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/memory.c b/memory.c
index 07c8315..a6b9da6 100644
--- a/memory.c
+++ b/memory.c
@@ -1948,6 +1948,14 @@ void memory_region_notify_one(IOMMUNotifier *notifier,
         return;
     }
 
+    if (entry->iova < notifier->start) {
+        entry->iova = notifier->start;
+    }
+
+    if (entry->iova + entry->addr_mask > notifier->end) {
+        entry->addr_mask = notifier->end - entry->iova;
+    }
+
     if (entry->perm & IOMMU_RW) {
         printf("map %lx %lx\n", entry->iova, entry->iova + entry->addr_mask);
         request_flags = IOMMU_NOTIFIER_MAP;
-- 
2.7.4