[Xen-changelog] Fail the build if NR_hypercalls is not a power of two.

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 8e78e6b391e00f0831e5fac485b1a0a8202e3e0e
# Parent  7a41b35d73f40246ea839a0628f50dd937b21d50
Fail the build if NR_hypercalls is not a power of two.
Making this requirement clearer originally suggested by
Muli Ben Yehuda.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r 7a41b35d73f4 -r 8e78e6b391e0 xen/include/asm-x86/config.h
--- a/xen/include/asm-x86/config.h      Mon Apr 10 16:28:02 2006
+++ b/xen/include/asm-x86/config.h      Mon Apr 10 16:32:30 2006
@@ -65,7 +65,12 @@
 
 #define barrier() __asm__ __volatile__("": : :"memory")
 
+/* A power-of-two value greater than or equal to number of hypercalls. */
 #define NR_hypercalls 32
+
+#if NR_hypercalls & (NR_hypercalls - 1)
+#error "NR_hypercalls must be a power-of-two value"
+#endif
 
 #ifndef NDEBUG
 #define MEMORY_GUARD

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