diff --git a/CODING_STYLE b/CODING_STYLE
index e3b1da6048..5644f1697f 100644
--- a/CODING_STYLE
+++ b/CODING_STYLE
@@ -157,43 +157,30 @@ Header inclusion guards
 -----------------------
 
 Unless otherwise specified, all header files should include proper
-guards to prevent multiple inclusions. The following naming conventions
-apply:
+guards to prevent multiple inclusions.  Guards need to be unique, and
+this property is checked by static analysis.
 
-- Guard names are derived from directory path underneath xen/ and the
-  actual file name.  Path components are separated by double
-  underscores.  Alphabetic characters are converted to upper case.  Non-
-  alphanumeric characters are replaced by single underscores.
-- Certain directory components are omitted, to keep identifier length
-  bounded:
-  - the top level include/,
-  - architecture-specific private files' arch/,
-  - any architecture's arch/<arch>/include/asm/ collapses to
-    ASM__<ARCH>__.
+Guards should be chosen based on the logical area, with enough
+disambiguation when the same filename exits in multiple locations in
+the source tree.  Commonly there should be a XEN or <arch> prefix.
+The guard should be spelt in ALL CAPITALS, ending with _H.
 
 For example:
 
-- Xen headers: XEN__<filename>_H
-  - include/xen/something.h -> XEN__SOMETHING_H
+- Xen headers: XEN_<something>_H
+  - include/xen/something.h -> XEN_SOMETHING_H
 
-- asm-generic headers: ASM_GENERIC__<filename>_H
-  - include/asm-generic/something.h -> ASM_GENERIC__SOMETHING_H
+- arch-specific headers: <arch>_<something>_H
+  - arch/x86/include/asm/something.h -> X86_SOMETHING_H
+  - arch/x86/include/asm/hvm/something.h -> X86_HVM_SOMETHING_H
+  - arch/x86/include/asm/pv/something.h -> X86_PV_SOMETHING_H
 
-- arch-specific headers: ASM__<architecture>__<subdir>__<filename>_H
-  - arch/x86/include/asm/something.h -> ASM__X86__SOMETHING_H
+- Private headers: <something>_PRIVATE_H
+  - common/something/private.h -> <SOMETHING>_PRIVATE_H
+  - drivers/foo/something.h -> <SOMETHING>_H
 
-- Private headers: <dir>__<filename>_H
-  - arch/arm/arm64/lib/something.h -> ARM__ARM64__LIB__SOMETHING_H
-  - arch/x86/lib/something.h -> X86__LIB__SOMETHING_H
-  - common/something.h -> COMMON__SOMETHING_H
-
-Note that this requires some discipline on the naming of future new
-sub-directories: There shouldn't be any other asm/ one anywhere, for
-example.  Nor should any new ports be named the same as top-level
-(within xen/) directories.  Which may in turn require some care if any
-new top-level directories were to be added.  Rule of thumb: Whenever
-adding a new subdirectory, check the rules to prevent any potential
-collisions.
+A good choice of guard is one that wont become stale if the
+driver/subsystem/etc is shuffled around the source tree.
 
 Emacs local variables
 ---------------------