Merge remote-tracking branch 'remotes/dgilbert/tags/pull-migration-20170906a' into staging

migration pull 2017-09-06

# gpg: Signature made Wed 06 Sep 2017 19:39:23 BST
# gpg:                using RSA key 0x0516331EBC5BFDE7
# gpg: Good signature from "Dr. David Alan Gilbert (RH2) <dgilbert@redhat.com>"
# gpg: WARNING: This key is not certified with sufficiently trusted signatures!
# gpg:          It is not certain that the signature belongs to the owner.
# Primary key fingerprint: 45F5 C71B 4A0C B7FB 977A  9FA9 0516 331E BC5B FDE7

* remotes/dgilbert/tags/pull-migration-20170906a:
  migration: dump str in migrate_set_state trace
  snapshot/tests: Try loadvm twice
  migration: Reset rather than destroy main_thread_load_event
  runstate/migrate: Two more transitions
  host-utils: Simplify pow2ceil()
  host-utils: Proactively fix pow2floor(), switch to unsigned
  xbzrle: Drop unused cache_resize()
  migration: Report when bdrv_inactivate_all fails

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 22 insertions, 14 deletions

diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index 95cf4f4..5ac621c 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -369,27 +369,35 @@ static inline bool is_power_of_2(uint64_t value)
     return !(value & (value - 1));
 }
 
-/* round down to the nearest power of 2*/
-static inline int64_t pow2floor(int64_t value)
+/**
+ * Return @value rounded down to the nearest power of two or zero.
+ */
+static inline uint64_t pow2floor(uint64_t value)
 {
-    if (!is_power_of_2(value)) {
-        value = 0x8000000000000000ULL >> clz64(value);
+    if (!value) {
+        /* Avoid undefined shift by 64 */
+        return 0;
     }
-    return value;
+    return 0x8000000000000000ull >> clz64(value);
 }
 
-/* round up to the nearest power of 2 (0 if overflow) */
+/*
+ * Return @value rounded up to the nearest power of two modulo 2^64.
+ * This is *zero* for @value > 2^63, so be careful.
+ */
 static inline uint64_t pow2ceil(uint64_t value)
 {
-    uint8_t nlz = clz64(value);
-
-    if (is_power_of_2(value)) {
-        return value;
-    }
-    if (!nlz) {
-        return 0;
+    int n = clz64(value - 1);
+
+    if (!n) {
+        /*
+         * @value - 1 has no leading zeroes, thus @value - 1 >= 2^63
+         * Therefore, either @value == 0 or @value > 2^63.
+         * If it's 0, return 1, else return 0.
+         */
+        return !value;
     }
-    return 1ULL << (64 - nlz);
+    return 0x8000000000000000ull >> (n - 1);
 }
 
 /**