[PULL 11/18] system/ram-discard-manager: implement replay via is_populated iteration

[Peter Xu <peterx@redhat.com>]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Replace the source-level replay wrappers with a new
replay_by_populated_state() helper that iterates the section at
min-granularity, calls is_populated() for each chunk, and aggregates
consecutive chunks of the same state before invoking the callback.

This moves the iteration logic from individual sources into the manager,
preparing for multi-source aggregation where the manager must combine
state from multiple sources anyway.

The replay_populated/replay_discarded vtable entries in
RamDiscardSourceClass are no longer called but remain in the interface
for now; they will be removed in follow-up commits along with the
now-dead source implementations.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: David Hildenbrand <david@kernel.org>
Link: https://lore.kernel.org/r/20260604-rdm5-v5-4-5768e6a0943d@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 system/ram-discard-manager.c | 85 ++++++++++++++++++++++++++----------
 1 file changed, 61 insertions(+), 24 deletions(-)

diff --git a/system/ram-discard-manager.c b/system/ram-discard-manager.c
index 1c9ff7fda5..a907ddf370 100644
--- a/system/ram-discard-manager.c
+++ b/system/ram-discard-manager.c
@@ -27,26 +27,65 @@ static bool ram_discard_source_is_populated(const RamDiscardSource *rds,
     return rdsc->is_populated(rds, section);
 }
 
-static int ram_discard_source_replay_populated(const RamDiscardSource *rds,
-                                               const MemoryRegionSection *section,
-                                               ReplayRamDiscardState replay_fn,
-                                               void *opaque)
+/*
+ * Iterate the section at source granularity, aggregating consecutive chunks
+ * with matching populated state, and call replay_fn for each run.
+ */
+static int replay_by_populated_state(const RamDiscardManager *rdm,
+                                     const MemoryRegionSection *section,
+                                     bool replay_populated,
+                                     ReplayRamDiscardState replay_fn,
+                                     void *opaque)
 {
-    RamDiscardSourceClass *rdsc = RAM_DISCARD_SOURCE_GET_CLASS(rds);
+    uint64_t granularity, offset, size, end, pos, run_start = 0;
+    bool in_run = false;
+    int ret = 0;
 
-    g_assert(rdsc->replay_populated);
-    return rdsc->replay_populated(rds, section, replay_fn, opaque);
-}
+    granularity = ram_discard_source_get_min_granularity(rdm->rds, rdm->mr);
+    offset = section->offset_within_region;
+    size = int128_get64(section->size);
+    end = offset + size;
+
+    /* Align iteration to granularity boundaries */
+    pos = QEMU_ALIGN_DOWN(offset, granularity);
+
+    for (; pos < end; pos += granularity) {
+        MemoryRegionSection chunk = {
+            .mr = section->mr,
+            .offset_within_region = pos,
+            .size = int128_make64(granularity),
+        };
+        bool populated = ram_discard_source_is_populated(rdm->rds, &chunk);
+
+        if (populated == replay_populated) {
+            if (!in_run) {
+                run_start = pos;
+                in_run = true;
+            }
+        } else if (in_run) {
+            MemoryRegionSection tmp = *section;
+
+            if (memory_region_section_intersect_range(&tmp, run_start,
+                                                      pos - run_start)) {
+                ret = replay_fn(&tmp, opaque);
+                if (ret) {
+                    return ret;
+                }
+            }
+            in_run = false;
+        }
+    }
 
-static int ram_discard_source_replay_discarded(const RamDiscardSource *rds,
-                                               const MemoryRegionSection *section,
-                                               ReplayRamDiscardState replay_fn,
-                                               void *opaque)
-{
-    RamDiscardSourceClass *rdsc = RAM_DISCARD_SOURCE_GET_CLASS(rds);
+    if (in_run) {
+        MemoryRegionSection tmp = *section;
 
-    g_assert(rdsc->replay_discarded);
-    return rdsc->replay_discarded(rds, section, replay_fn, opaque);
+        if (memory_region_section_intersect_range(&tmp, run_start,
+                                                  pos - run_start)) {
+            ret = replay_fn(&tmp, opaque);
+        }
+    }
+
+    return ret;
 }
 
 RamDiscardManager *ram_discard_manager_new(MemoryRegion *mr,
@@ -78,8 +117,7 @@ int ram_discard_manager_replay_populated(const RamDiscardManager *rdm,
                                          ReplayRamDiscardState replay_fn,
                                          void *opaque)
 {
-    return ram_discard_source_replay_populated(rdm->rds, section,
-                                               replay_fn, opaque);
+    return replay_by_populated_state(rdm, section, true, replay_fn, opaque);
 }
 
 int ram_discard_manager_replay_discarded(const RamDiscardManager *rdm,
@@ -87,8 +125,7 @@ int ram_discard_manager_replay_discarded(const RamDiscardManager *rdm,
                                          ReplayRamDiscardState replay_fn,
                                          void *opaque)
 {
-    return ram_discard_source_replay_discarded(rdm->rds, section,
-                                               replay_fn, opaque);
+    return replay_by_populated_state(rdm, section, false, replay_fn, opaque);
 }
 
 static void ram_discard_manager_initfn(Object *obj)
@@ -182,8 +219,8 @@ void ram_discard_manager_register_listener(RamDiscardManager *rdm,
     rdl->section = memory_region_section_new_copy(section);
     QLIST_INSERT_HEAD(&rdm->rdl_list, rdl, next);
 
-    ret = ram_discard_source_replay_populated(rdm->rds, rdl->section,
-                                              rdm_populate_cb, rdl);
+    ret = ram_discard_manager_replay_populated(rdm, rdl->section,
+                                               rdm_populate_cb, rdl);
     if (ret) {
         error_report("%s: Replaying populated ranges failed: %s", __func__,
                      strerror(-ret));
@@ -208,8 +245,8 @@ int ram_discard_manager_replay_populated_to_listeners(RamDiscardManager *rdm)
     int ret = 0;
 
     QLIST_FOREACH(rdl, &rdm->rdl_list, next) {
-        ret = ram_discard_source_replay_populated(rdm->rds, rdl->section,
-                                                  rdm_populate_cb, rdl);
+        ret = ram_discard_manager_replay_populated(rdm, rdl->section,
+                                                   rdm_populate_cb, rdl);
         if (ret) {
             break;
         }
-- 
2.54.0