[PATCH 5/7] xen/bitops: Implement ffs64() in common logic

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

As per ffs()/ffsl() in previous patches.  Add tests for all interesting bit
positions at 32bit boundaries.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
CC: Michal Orzel <michal.orzel@xxxxxxx>
CC: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
CC: Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>
CC: consulting@xxxxxxxxxxx <consulting@xxxxxxxxxxx>
CC: Simone Ballarin <simone.ballarin@xxxxxxxxxxx>
CC: Federico Serafini <federico.serafini@xxxxxxxxxxx>
CC: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
---
 xen/common/bitops.c      | 12 ++++++++++++
 xen/include/xen/bitops.h | 16 ++++++++--------
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/xen/common/bitops.c b/xen/common/bitops.c
index eceffe5029d6..cd194fe672b7 100644
--- a/xen/common/bitops.c
+++ b/xen/common/bitops.c
@@ -47,6 +47,18 @@ static void test_ffs(void)
     CHECK(ffsl, 1UL << (BITS_PER_LONG - 1), BITS_PER_LONG);
     if ( BITS_PER_LONG > 32 )
         CHECK(ffsl, 1UL << 32, 33);
+
+    /*
+     * unsigned int ffs64(uint64_t)
+     *
+     * 32-bit builds of Xen have to split this into two adjacent operations,
+     * so test all interesting bit positions.
+     */
+    CHECK(ffs64, 0, 0);
+    CHECK(ffs64, 1, 1);
+    CHECK(ffs64, (uint64_t)0x0000000080000000, 32);
+    CHECK(ffs64, (uint64_t)0x0000000100000000, 33);
+    CHECK(ffs64, (uint64_t)0x8000000000000000, 64);
 }
 
 static int __init cf_check test_bitops(void)
diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h
index b85b35c40781..f14ad0d33aa3 100644
--- a/xen/include/xen/bitops.h
+++ b/xen/include/xen/bitops.h
@@ -96,6 +96,14 @@ static always_inline __pure unsigned int ffsl(unsigned long 
x)
     return arch_ffsl(x);
 }
 
+static always_inline __pure unsigned int ffs64(uint64_t x)
+{
+    if ( BITS_PER_LONG == 64 )
+        return ffsl(x);
+    else
+        return !x || (uint32_t)x ? ffs(x) : ffs(x >> 32) + 32;
+}
+
 /* --------------------- Please tidy below here --------------------- */
 
 #ifndef find_next_bit
@@ -148,15 +156,7 @@ extern unsigned long find_first_zero_bit(const unsigned 
long *addr,
 
 #if BITS_PER_LONG == 64
 # define fls64 flsl
-# define ffs64 ffsl
 #else
-# ifndef ffs64
-static inline int generic_ffs64(__u64 x)
-{
-    return !x || (__u32)x ? ffs(x) : ffs(x >> 32) + 32;
-}
-#  define ffs64 generic_ffs64
-# endif
 # ifndef fls64
 static inline int generic_fls64(__u64 x)
 {
-- 
2.30.2