memory: prepare for multiple bits in the dirty log mask

When the dirty log mask will also cover other bits than DIRTY_MEMORY_VGA,
some listeners may be interested in the overall zero/non-zero value of
the dirty log mask; others may be interested in the value of single bits.

For this reason, always call log_start/log_stop if bits have respectively
appeared or disappeared, and pass the old and new values of the dirty log
mask so that listeners can distinguish the kinds of change.

For example, KVM checks if dirty logging used to be completely disabled
(in log_start) or is now completely disabled (in log_stop).  On the
other hand, Xen has to check manually if DIRTY_MEMORY_VGA changed,
since that is the only bit it cares about.

Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

5 files changed, 44 insertions, 19 deletions

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 53d23d281d..a7fe3c5104 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -676,13 +676,15 @@ static void vhost_log_global_stop(MemoryListener *listener)
 }
 
 static void vhost_log_start(MemoryListener *listener,
-                            MemoryRegionSection *section)
+                            MemoryRegionSection *section,
+                            int old, int new)
 {
     /* FIXME: implement */
 }
 
 static void vhost_log_stop(MemoryListener *listener,
-                           MemoryRegionSection *section)
+                           MemoryRegionSection *section,
+                           int old, int new)
 {
     /* FIXME: implement */
 }
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 156d506063..55dc11d55c 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -206,8 +206,10 @@ struct MemoryListener {
     void (*region_add)(MemoryListener *listener, MemoryRegionSection *section);
     void (*region_del)(MemoryListener *listener, MemoryRegionSection *section);
     void (*region_nop)(MemoryListener *listener, MemoryRegionSection *section);
-    void (*log_start)(MemoryListener *listener, MemoryRegionSection *section);
-    void (*log_stop)(MemoryListener *listener, MemoryRegionSection *section);
+    void (*log_start)(MemoryListener *listener, MemoryRegionSection *section,
+                      int old, int new);
+    void (*log_stop)(MemoryListener *listener, MemoryRegionSection *section,
+                     int old, int new);
     void (*log_sync)(MemoryListener *listener, MemoryRegionSection *section);
     void (*log_global_start)(MemoryListener *listener);
     void (*log_global_stop)(MemoryListener *listener);
diff --git a/kvm-all.c b/kvm-all.c
index d5416bbd74..c713b22f8c 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -344,10 +344,15 @@ static int kvm_dirty_pages_log_change(hwaddr phys_addr,
 }
 
 static void kvm_log_start(MemoryListener *listener,
-                          MemoryRegionSection *section)
+                          MemoryRegionSection *section,
+                          int old, int new)
 {
     int r;
 
+    if (old != 0) {
+        return;
+    }
+
     r = kvm_dirty_pages_log_change(section->offset_within_address_space,
                                    int128_get64(section->size), true);
     if (r < 0) {
@@ -356,10 +361,15 @@ static void kvm_log_start(MemoryListener *listener,
 }
 
 static void kvm_log_stop(MemoryListener *listener,
-                          MemoryRegionSection *section)
+                          MemoryRegionSection *section,
+                          int old, int new)
 {
     int r;
 
+    if (new != 0) {
+        return;
+    }
+
     r = kvm_dirty_pages_log_change(section->offset_within_address_space,
                                    int128_get64(section->size), false);
     if (r < 0) {
diff --git a/memory.c b/memory.c
index 72e33e853b..3e3d5b8ad6 100644
--- a/memory.c
+++ b/memory.c
@@ -152,7 +152,7 @@ static bool memory_listener_match(MemoryListener *listener,
     } while (0)
 
 /* No need to ref/unref .mr, the FlatRange keeps it alive.  */
-#define MEMORY_LISTENER_UPDATE_REGION(fr, as, dir, callback)            \
+#define MEMORY_LISTENER_UPDATE_REGION(fr, as, dir, callback, _args...)  \
     MEMORY_LISTENER_CALL(callback, dir, (&(MemoryRegionSection) {       \
         .mr = (fr)->mr,                                                 \
         .address_space = (as),                                          \
@@ -160,7 +160,7 @@ static bool memory_listener_match(MemoryListener *listener,
         .size = (fr)->addr.size,                                        \
         .offset_within_address_space = int128_get64((fr)->addr.start),  \
         .readonly = (fr)->readonly,                                     \
-              }))
+              }), ##_args)
 
 struct CoalescedMemoryRange {
     AddrRange addr;
@@ -774,10 +774,15 @@ static void address_space_update_topology_pass(AddressSpace *as,
 
             if (adding) {
                 MEMORY_LISTENER_UPDATE_REGION(frnew, as, Forward, region_nop);
-                if (frold->dirty_log_mask && !frnew->dirty_log_mask) {
-                    MEMORY_LISTENER_UPDATE_REGION(frnew, as, Reverse, log_stop);
-                } else if (frnew->dirty_log_mask && !frold->dirty_log_mask) {
-                    MEMORY_LISTENER_UPDATE_REGION(frnew, as, Forward, log_start);
+                if (frnew->dirty_log_mask & ~frold->dirty_log_mask) {
+                    MEMORY_LISTENER_UPDATE_REGION(frnew, as, Forward, log_start,
+                                                  frold->dirty_log_mask,
+                                                  frnew->dirty_log_mask);
+                }
+                if (frold->dirty_log_mask & ~frnew->dirty_log_mask) {
+                    MEMORY_LISTENER_UPDATE_REGION(frnew, as, Reverse, log_stop,
+                                                  frold->dirty_log_mask,
+                                                  frnew->dirty_log_mask);
                 }
             }
 
diff --git a/xen-hvm.c b/xen-hvm.c
index 338ab291f8..42356b836a 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -646,21 +646,27 @@ static void xen_sync_dirty_bitmap(XenIOState *state,
 }
 
 static void xen_log_start(MemoryListener *listener,
-                          MemoryRegionSection *section)
+                          MemoryRegionSection *section,
+                          int old, int new)
 {
     XenIOState *state = container_of(listener, XenIOState, memory_listener);
 
-    xen_sync_dirty_bitmap(state, section->offset_within_address_space,
-                          int128_get64(section->size));
+    if (new & ~old & (1 << DIRTY_MEMORY_VGA)) {
+        xen_sync_dirty_bitmap(state, section->offset_within_address_space,
+                              int128_get64(section->size));
+    }
 }
 
-static void xen_log_stop(MemoryListener *listener, MemoryRegionSection *section)
+static void xen_log_stop(MemoryListener *listener, MemoryRegionSection *section,
+                         int old, int new)
 {
     XenIOState *state = container_of(listener, XenIOState, memory_listener);
 
-    state->log_for_dirtybit = NULL;
-    /* Disable dirty bit tracking */
-    xc_hvm_track_dirty_vram(xen_xc, xen_domid, 0, 0, NULL);
+    if (old & ~new & (1 << DIRTY_MEMORY_VGA)) {
+        state->log_for_dirtybit = NULL;
+        /* Disable dirty bit tracking */
+        xc_hvm_track_dirty_vram(xen_xc, xen_domid, 0, 0, NULL);
+    }
 }
 
 static void xen_log_sync(MemoryListener *listener, MemoryRegionSection *section)