[Xen-devel] [PATCH v4.1 1/3] libxl/cpumap: Add xc_cpumap_[setcpu, clearcpu, testcpu] to complement xc_cpumap_alloc.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

We export the xc_cpumap_alloc but not the bit operations.
One could include 'xc_bitops.h' but that is naughty - so instead
we just export the proper functions to do it on the xc_cpumap_t
typedef.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
----
v2: Use our own macro to make sure ARM is not affected negatively
v3: Lifted Ian's explanation.
---
 tools/libxc/include/xenctrl.h |  9 +++++++++
 tools/libxc/xc_misc.c         | 26 ++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 6994c51..2c17d78 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -395,6 +395,15 @@ int xc_get_cpumap_size(xc_interface *xch);
 /* allocate a cpumap */
 xc_cpumap_t xc_cpumap_alloc(xc_interface *xch);
 
+/* clear an CPU from the cpumap. */
+void xc_cpumap_clearcpu(int cpu, xc_cpumap_t map);
+
+/* set an CPU in the cpumap. */
+void xc_cpumap_setcpu(int cpu, xc_cpumap_t map);
+
+/* Test whether the CPU in cpumap is set. */
+int xc_cpumap_testcpu(int cpu, xc_cpumap_t map);
+
 /*
  * NODEMAP handling
  */
diff --git a/tools/libxc/xc_misc.c b/tools/libxc/xc_misc.c
index be68291..3a1784b 100644
--- a/tools/libxc/xc_misc.c
+++ b/tools/libxc/xc_misc.c
@@ -18,6 +18,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  
USA
  */
 
+#include "xc_bitops.h"
 #include "xc_private.h"
 #include <xen/hvm/hvm_op.h>
 
@@ -93,6 +94,31 @@ xc_cpumap_t xc_cpumap_alloc(xc_interface *xch)
     return calloc(1, sz);
 }
 
+/*
+ * xc_bitops.h has macros that do this as well - however they assume that
+ * the bitmask is word aligned but xc_cpumap_t is only guaranteed to be
+ * byte aligned and so we need byte versions for architectures which do
+ * not support misaligned accesses (which is basically everyone
+ * but x86, although even on x86 it can be inefficient).
+ */
+#define BITS_PER_CPUMAP(map) (sizeof(*map) * 8)
+#define CPUMAP_ENTRY(cpu, map) ((map))[(cpu) / BITS_PER_CPUMAP(map)]
+#define CPUMAP_SHIFT(cpu, map) ((cpu) % BITS_PER_CPUMAP(map))
+void xc_cpumap_clearcpu(int cpu, xc_cpumap_t map)
+{
+    CPUMAP_ENTRY(cpu, map) &= ~(1U << CPUMAP_SHIFT(cpu, map));
+}
+
+void xc_cpumap_setcpu(int cpu, xc_cpumap_t map)
+{
+    CPUMAP_ENTRY(cpu, map) |= (1U << CPUMAP_SHIFT(cpu, map));
+}
+
+int xc_cpumap_testcpu(int cpu, xc_cpumap_t map)
+{
+    return (CPUMAP_ENTRY(cpu, map) >> CPUMAP_SHIFT(cpu, map)) & 1;
+}
+
 xc_nodemap_t xc_nodemap_alloc(xc_interface *xch)
 {
     int sz;
-- 
2.1.0


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