[Qemu-devel] [PATCH 3/4] dump: populate guest_phys_blocks

[Laszlo Ersek <lersek@redhat.com>]

While the machine is paused, in guest_phys_blocks_append() we register a
one-shot MemoryListener, solely for the initial collection of the valid
guest-physical memory ranges that happens at client registration time.

For each range that is reported to guest_phys_blocks_set_memory(), we
attempt to merge the range with adjacent (preceding, subsequent, or both)
ranges. We use two hash tables for this purpose, both indexing the same
ranges, just by different keys (guest-phys-start vs. guest-phys-end).

Ranges can only be joined if they are contiguous in both guest-physical
address space, and contiguous in host virtual address space.

The "maximal" ranges that remain in the end constitute the guest-physical
memory map that the dump will be based on.

Related RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=981582

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 include/sysemu/memory_mapping.h |    1 +
 dump.c                          |    2 +-
 memory_mapping.c                |  135 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 137 insertions(+), 1 deletions(-)

diff --git a/include/sysemu/memory_mapping.h b/include/sysemu/memory_mapping.h
index 53c2cd5..6723dc5 100644
--- a/include/sysemu/memory_mapping.h
+++ b/include/sysemu/memory_mapping.h
@@ -66,6 +66,7 @@ void memory_mapping_list_init(MemoryMappingList *list);
 
 void guest_phys_blocks_free(GuestPhysBlockList *list);
 void guest_phys_blocks_init(GuestPhysBlockList *list);
+void guest_phys_blocks_append(GuestPhysBlockList *list);
 
 void qemu_get_guest_memory_mapping(MemoryMappingList *list, Error **errp);
 
diff --git a/dump.c b/dump.c
index 716fb1d..3fa33fc 100644
--- a/dump.c
+++ b/dump.c
@@ -746,7 +746,7 @@ static int dump_init(DumpState *s, int fd, bool paging, bool has_filter,
     s->length = length;
 
     guest_phys_blocks_init(&s->guest_phys_blocks);
-    /* FILL LIST */
+    guest_phys_blocks_append(&s->guest_phys_blocks);
 
     s->start = get_start_block(s);
     if (s->start == -1) {
diff --git a/memory_mapping.c b/memory_mapping.c
index c70505b..efaabf8 100644
--- a/memory_mapping.c
+++ b/memory_mapping.c
@@ -11,9 +11,13 @@
  *
  */
 
+#include <glib.h>
+
 #include "cpu.h"
 #include "exec/cpu-all.h"
 #include "sysemu/memory_mapping.h"
+#include "exec/memory.h"
+#include "exec/address-spaces.h"
 
 static void memory_mapping_list_add_mapping_sorted(MemoryMappingList *list,
                                                    MemoryMapping *mapping)
@@ -182,6 +186,137 @@ void guest_phys_blocks_init(GuestPhysBlockList *list)
     QTAILQ_INIT(&list->head);
 }
 
+typedef struct GuestPhysListener {
+    GHashTable *by_target_start;
+    GHashTable *by_target_end;
+    MemoryListener listener;
+} GuestPhysListener;
+
+static void guest_phys_blocks_region_add(MemoryListener *listener,
+                                         MemoryRegionSection *section)
+{
+    GuestPhysListener *g;
+    uint64_t section_size;
+    hwaddr target_start, target_end;
+    uint8_t *host_addr;
+    GuestPhysBlock *predecessor, *successor, *block;
+    bool found;
+
+    /* we only care about RAM */
+    if (!memory_region_is_ram(section->mr)) {
+        return;
+    }
+
+    g            = container_of(listener, GuestPhysListener, listener);
+    section_size = int128_get64(section->size);
+    target_start = section->offset_within_address_space;
+    target_end   = target_start + section_size;
+    host_addr    = memory_region_get_ram_ptr(section->mr) +
+                   section->offset_within_region;
+
+    /* find continuity in guest physical address space */
+    predecessor = g_hash_table_lookup(g->by_target_end,   &target_start);
+    successor   = g_hash_table_lookup(g->by_target_start, &target_end);
+
+    /* we require continuity in host memory too */
+    if (predecessor != NULL) {
+        hwaddr predecessor_size = predecessor->target_end -
+                                  predecessor->target_start;
+        if (predecessor->host_addr + predecessor_size != host_addr) {
+            predecessor = NULL;
+        }
+    }
+    if (successor != NULL
+        && host_addr + section_size != successor->host_addr) {
+        successor = NULL;
+    }
+
+    if (predecessor == NULL) {
+        if (successor == NULL) {
+            /* Isolated mapping, allocate it and add it to both tables. */
+            block = g_malloc0(sizeof *block);
+
+            block->target_end = target_end;
+            g_hash_table_insert(g->by_target_end, &block->target_end, block);
+        } else {
+            /* Mapping has successor only. Merge current into successor by
+             * modifying successor's start. Successor's end doesn't change.
+             */
+            block = successor;
+            found = g_hash_table_steal(g->by_target_start,
+                                       &block->target_start);
+            g_assert(found);
+        }
+        block->target_start = target_start;
+        block->host_addr    = host_addr;
+        g_hash_table_insert(g->by_target_start, &block->target_start, block);
+        return;
+    }
+
+    if (successor != NULL) {
+        /* Mapping has both predecessor and successor. Delete the successor
+         * and expand the predecessor to cover all three.
+         */
+        target_end = successor->target_end;
+
+        found = g_hash_table_steal(g->by_target_end, &successor->target_end);
+        g_assert(found);
+        found = g_hash_table_steal(g->by_target_start,
+                                   &successor->target_start);
+        g_assert(found);
+
+        g_free(successor);
+    }
+    /* otherwise, mapping has predecessor only */
+
+    /* Expand predecessor until @target_end. Predecessor's start doesn't
+     * change.
+     */
+    block = predecessor;
+    found = g_hash_table_steal(g->by_target_end, &block->target_end);
+    g_assert(found);
+
+    block->target_end = target_end;
+    g_hash_table_insert(g->by_target_end, &block->target_end, block);
+}
+
+static void guest_phys_block_link(gpointer key, gpointer value,
+                                  gpointer user_data)
+{
+    GuestPhysBlock *block = value;
+    GuestPhysBlockList *list = user_data;
+
+    QTAILQ_INSERT_TAIL(&list->head, block, next);
+    ++list->num;
+}
+
+void guest_phys_blocks_append(GuestPhysBlockList *list)
+{
+    GHashFunc hash_func;
+    GEqualFunc equal_func;
+    GuestPhysListener g = { 0 };
+
+    if (sizeof(hwaddr) == sizeof(uint64_t)) {
+        hash_func  = &g_int64_hash;
+        equal_func = &g_int64_equal;
+    } else {
+        hash_func  = &g_int_hash;
+        equal_func = &g_int_equal;
+    }
+
+    g.by_target_start = g_hash_table_new(hash_func, equal_func);
+    g.by_target_end   = g_hash_table_new(hash_func, equal_func);
+
+    g.listener.region_add = &guest_phys_blocks_region_add;
+    memory_listener_register(&g.listener, &address_space_memory);
+    memory_listener_unregister(&g.listener);
+
+    g_hash_table_foreach(g.by_target_start, &guest_phys_block_link, list);
+
+    g_hash_table_destroy(g.by_target_end);
+    g_hash_table_destroy(g.by_target_start);
+}
+
 static CPUState *find_paging_enabled_cpu(CPUState *start_cpu)
 {
     CPUState *cpu;
-- 
1.7.1