migration/multifd: Support incoming mapped-ram stream format

For the incoming mapped-ram migration we need to read the ramblock
headers, get the pages bitmap and send the host address of each
non-zero page to the multifd channel thread for writing.

Usage on HMP is:

(qemu) migrate_set_capability multifd on
(qemu) migrate_set_capability mapped-ram on
(qemu) migrate_incoming file:migfile

(the ram.h include needs to move because we've been previously relying
on it being included from migration.c. Now file.h will start including
multifd.h before migration.o is processed)

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-22-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>

1 files changed, 24 insertions, 2 deletions

diff --git a/migration/ram.c b/migration/ram.c
index 87cb73fd76..1f1b5297cf 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3952,6 +3952,22 @@ void colo_flush_ram_cache(void)
     trace_colo_flush_ram_cache_end();
 }
 
+static size_t ram_load_multifd_pages(void *host_addr, size_t size,
+                                     uint64_t offset)
+{
+    MultiFDRecvData *data = multifd_get_recv_data();
+
+    data->opaque = host_addr;
+    data->file_offset = offset;
+    data->size = size;
+
+    if (!multifd_recv()) {
+        return 0;
+    }
+
+    return size;
+}
+
 static bool read_ramblock_mapped_ram(QEMUFile *f, RAMBlock *block,
                                      long num_pages, unsigned long *bitmap,
                                      Error **errp)
@@ -3981,8 +3997,14 @@ static bool read_ramblock_mapped_ram(QEMUFile *f, RAMBlock *block,
 
             size = MIN(unread, MAPPED_RAM_LOAD_BUF_SIZE);
 
-            read = qemu_get_buffer_at(f, host, size,
-                                      block->pages_offset + offset);
+            if (migrate_multifd()) {
+                read = ram_load_multifd_pages(host, size,
+                                              block->pages_offset + offset);
+            } else {
+                read = qemu_get_buffer_at(f, host, size,
+                                          block->pages_offset + offset);
+            }
+
             if (!read) {
                 goto err;
             }