[PATCH v7 20/23] vfio: Bypass readonly region for dirty tracking

[Zhenzhong Duan <zhenzhong.duan@intel.com>]

When doing ditry tracking or calculating dirty tracking range, readonly
regions can be bypassed, because corresponding DMA mappings are readonly
and never become dirty.

This can optimize dirty tracking a bit for passthrough device.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 hw/vfio/listener.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/hw/vfio/listener.c b/hw/vfio/listener.c
index 0862b2b834..cbd86c79af 100644
--- a/hw/vfio/listener.c
+++ b/hw/vfio/listener.c
@@ -828,7 +828,8 @@ static void vfio_dirty_tracking_update(MemoryListener *listener,
         container_of(listener, VFIODirtyRangesListener, listener);
     hwaddr iova, end;
 
-    if (!vfio_listener_valid_section(section, false, "tracking_update") ||
+    /* Bypass readonly section as it never become dirty */
+    if (!vfio_listener_valid_section(section, true, "tracking_update") ||
         !vfio_get_section_iova_range(dirty->bcontainer, section,
                                      &iova, &end, NULL)) {
         return;
@@ -1087,6 +1088,12 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
     if (!mr) {
         goto out_unlock;
     }
+
+    if (!(iotlb->perm & IOMMU_WO) || mr->readonly) {
+        rcu_read_unlock();
+        return;
+    }
+
     translated_addr = memory_region_get_ram_addr(mr) + xlat;
 
     ret = vfio_container_query_dirty_bitmap(bcontainer, iova, iotlb->addr_mask + 1,
@@ -1222,7 +1229,7 @@ static void vfio_listener_log_sync(MemoryListener *listener,
     int ret;
     Error *local_err = NULL;
 
-    if (vfio_listener_skipped_section(section, false)) {
+    if (vfio_listener_skipped_section(section, true)) {
         return;
     }
 
-- 
2.47.1