[PATCH kvm-unit-tests] api: verify number of dirty pages

[Paolo Bonzini <pbonzini@redhat.com>]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 api/dirty-log-perf.cc |  6 +++---
 api/memmap.cc         | 15 ++++++++++++++-
 api/memmap.hh         |  2 +-
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/api/dirty-log-perf.cc b/api/dirty-log-perf.cc
index 89043b0..f87b4b4 100644
--- a/api/dirty-log-perf.cc
+++ b/api/dirty-log-perf.cc
@@ -52,11 +52,11 @@ void check_dirty_log(kvm::vcpu& vcpu, mem_slot& slot, void* slot_head)
         do_guest_write(vcpu, slot_head, i, nr_slot_pages);
 
         uint64_t start_ns = time_ns();
-        slot.update_dirty_log();
+        int n = slot.update_dirty_log();
         uint64_t end_ns = time_ns();
 
-        printf("get dirty log: %10lld ns for %10lld dirty pages\n",
-               end_ns - start_ns, i);
+        printf("get dirty log: %10lld ns for %10d dirty pages (expected %lld)\n",
+               end_ns - start_ns, n, i);
     }
 
     slot.set_dirty_logging(false);
diff --git a/api/memmap.cc b/api/memmap.cc
index 041e84a..cf44824 100644
--- a/api/memmap.cc
+++ b/api/memmap.cc
@@ -1,5 +1,6 @@
 
 #include "memmap.hh"
+#include <numeric>
 
 mem_slot::mem_slot(mem_map& map, uint64_t gpa, uint64_t size, void* hva)
     : _map(map)
@@ -60,9 +61,21 @@ bool mem_slot::dirty_logging() const
     return _dirty_log_enabled;
 }
 
-void mem_slot::update_dirty_log()
+static inline int hweight(uint64_t w)
+{
+    w -= (w >> 1) & 0x5555555555555555;
+    w =  (w & 0x3333333333333333) + ((w >> 2) & 0x3333333333333333);
+    w =  (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0f;
+    return (w * 0x0101010101010101) >> 56;
+}
+
+int mem_slot::update_dirty_log()
 {
     _map._vm.get_dirty_log(_slot, &_log[0]);
+    return std::accumulate(_log.begin(), _log.end(), 0,
+                           [] (int prev, ulong elem) -> int {
+                               return prev + hweight(elem);
+                           });
 }
 
 bool mem_slot::is_dirty(uint64_t gpa) const
diff --git a/api/memmap.hh b/api/memmap.hh
index 59ec619..48711ae 100644
--- a/api/memmap.hh
+++ b/api/memmap.hh
@@ -15,7 +15,7 @@ public:
     ~mem_slot();
     void set_dirty_logging(bool enabled);
     bool dirty_logging() const;
-    void update_dirty_log();
+    int update_dirty_log();
     bool is_dirty(uint64_t gpa) const;
 private:
     void update();
-- 
1.8.3.1