[PATCH v3 9/9] hvf: remove the need to lookup memory slots when clearing dirty-bits

[Yan-Jie Wang]

Originally, when log_clear gets called, log_clear calls
hvf_set_dirty_tracking to write-protect memory slots whose dirty-bits
are cleared.

Calling hvf_set_dirty_tracking means that memory slots will be
look up and the lock for memory slots will be held during the call.

We can use the parameter `section` passed by the caller to determine the
pages that need to be write-protected. Compared to the original method,
this saves time.

Moreover, this makes only pages whose dirty-bits
are cleared write-protected instead of making the whole memory slot
write-protected.

Signed-off-by: Yan-Jie Wang <ubzeme@gmail.com>
---
 accel/hvf/hvf-mem.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/accel/hvf/hvf-mem.c b/accel/hvf/hvf-mem.c
index 60ece20eb4..47d23faec8 100644
--- a/accel/hvf/hvf-mem.c
+++ b/accel/hvf/hvf-mem.c
@@ -84,7 +84,10 @@ static hwaddr hvf_align_section(MemoryRegionSection *section,
     size = (size - _delta) & qemu_real_host_page_mask;
 
     *start = _start;
-    *delta = _delta;
+
+    if (delta) {
+        *delta = _delta;
+    }
 
     return size;
 }
@@ -230,11 +233,27 @@ static void hvf_log_stop(MemoryListener *listener,
 static void hvf_log_clear(MemoryListener *listener,
                          MemoryRegionSection *section)
 {
+    hwaddr start, size;
+
+    if (!memory_region_is_ram(section->mr) ||
+        memory_region_is_rom(section->mr)) {
+        /* do not consider memory regions which are not directly writeable */
+        return;
+    }
+
+    if (!memory_region_get_dirty_log_mask(section->mr)) {
+        /* the region is not being dirty-tracked */
+        return;
+    }
+
     /*
      * The dirty bits are being cleared.
      * Make the section write-protected again.
      */
-    hvf_set_dirty_tracking(section, 1);
+    size = hvf_align_section(section, &start, NULL);
+    if (size) {
+        hv_vm_protect(start, size, HV_MEMORY_READ | HV_MEMORY_EXEC);
+    }
 }
 
 static void hvf_region_add(MemoryListener *listener,
-- 
2.32.0 (Apple Git-132)