Changeset 80804 in vbox for trunk/src/VBox/VMM

Timestamp:

Sep 16, 2019 5:40:46 AM (5 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

133371

Message:

VMM/CPUM: Nested VMX: bugref:9180 Clarify I/O port wrap around.

File:

• trunk/src/VBox/VMM/VMMAll/CPUMAllRegs.cpp (modified) (1 diff)

trunk/src/VBox/VMM/VMMAll/CPUMAllRegs.cpp

@@ -2435 +2435 @@
      * VM-exit.
      *
+     * Reading 1, 2, 4 bytes at ports 0xffff, 0xfffe and 0xfffc are valid and do not
+     * constitute a wrap around. However, reading 2 bytes at port 0xffff or 4 bytes
+     * from port 0xffff/0xfffe/0xfffd constitute a wrap around. In other words, any
+     * access to -both- ports 0xffff and port 0 is a wrap around.
+     *
      * See Intel spec. 25.1.3 "Instructions That Cause VM Exits Conditionally".
      */
-    /** @todo r=ramshankar: Reading 1, 2, 4 bytes at ports 0xfffe, 0xfffd and 0xfffb
-     *        respectively are valid and do not constitute a wrap around from what I
-     *        understand. Verify this later. */
+    /** @todo r=ramshankar: . Verify this later. */
     uint32_t const uPortLast = uPort + cbAccess;
     if (uPortLast > 0x10000)