KVM: MMU: document clear_spte_count

[deliverable/linux.git] / Documentation / virtual / kvm / mmu.txt

diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
index 869abcc48315874820d9609675149d2bc4510aff..f514a3fad9b983be1d03af8fb2fd86b390579979 100644 (file)
--- a/Documentation/virtual/kvm/mmu.txt
+++ b/Documentation/virtual/kvm/mmu.txt
@@ -210,6 +210,11 @@ Shadow pages contain the following information:
     A bitmap indicating which sptes in spt point (directly or indirectly) at
     pages that may be unsynchronized.  Used to quickly locate all unsychronized
     pages reachable from a given page.
+  clear_spte_count:
+    Only present on 32-bit hosts, where a 64-bit spte cannot be written
+    atomically.  The reader uses this while running out of the MMU lock
+    to detect in-progress updates and retry them until the writer has
+    finished the write.
 
 Reverse map
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