Merge tag 'migration-20250310-pull-request' of https://gitlab.com/farosas/qemu into staging

Migration pull request

- Fix use-after-free in incoming migration
- Improve cpr migration blocker for volatile ram
- Fix RDMA migration

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# gpg: Good signature from "Fabiano Rosas <farosas@suse.de>" [unknown]
# gpg:                 aka "Fabiano Almeida Rosas <fabiano.rosas@suse.com>" [unknown]
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* tag 'migration-20250310-pull-request' of https://gitlab.com/farosas/qemu:
  migration: Prioritize RDMA in ram_save_target_page()
  migration: ram block cpr blockers
  migration: Fix UAF for incoming migration on MigrationState

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 66 insertions, 0 deletions

diff --git a/system/physmem.c b/system/physmem.c
index a6af555f4b..e97de3ef65 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -71,7 +71,10 @@
 
 #include "qemu/pmem.h"
 
+#include "qapi/qapi-types-migration.h"
+#include "migration/blocker.h"
 #include "migration/cpr.h"
+#include "migration/options.h"
 #include "migration/vmstate.h"
 
 #include "qemu/range.h"
@@ -1904,6 +1907,14 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
             qemu_mutex_unlock_ramlist();
             goto out_free;
         }
+
+        error_setg(&new_block->cpr_blocker,
+                   "Memory region %s uses guest_memfd, "
+                   "which is not supported with CPR.",
+                   memory_region_name(new_block->mr));
+        migrate_add_blocker_modes(&new_block->cpr_blocker, errp,
+                                  MIG_MODE_CPR_TRANSFER,
+                                  -1);
     }
 
     ram_size = (new_block->offset + new_block->max_length) >> TARGET_PAGE_BITS;
@@ -4095,3 +4106,58 @@ bool ram_block_discard_is_required(void)
     return qatomic_read(&ram_block_discard_required_cnt) ||
            qatomic_read(&ram_block_coordinated_discard_required_cnt);
 }
+
+/*
+ * Return true if ram is compatible with CPR.  Do not exclude rom,
+ * because the rom file could change in new QEMU.
+ */
+static bool ram_is_cpr_compatible(RAMBlock *rb)
+{
+    MemoryRegion *mr = rb->mr;
+
+    if (!mr || !memory_region_is_ram(mr)) {
+        return true;
+    }
+
+    /* Ram device is remapped in new QEMU */
+    if (memory_region_is_ram_device(mr)) {
+        return true;
+    }
+
+    /*
+     * A file descriptor is passed to new QEMU and remapped, or its backing
+     * file is reopened and mapped.  It must be shared to avoid COW.
+     */
+    if (rb->fd >= 0 && qemu_ram_is_shared(rb)) {
+        return true;
+    }
+
+    return false;
+}
+
+/*
+ * Add a blocker for each volatile ram block.  This function should only be
+ * called after we know that the block is migratable.  Non-migratable blocks
+ * are either re-created in new QEMU, or are handled specially, or are covered
+ * by a device-level CPR blocker.
+ */
+void ram_block_add_cpr_blocker(RAMBlock *rb, Error **errp)
+{
+    assert(qemu_ram_is_migratable(rb));
+
+    if (ram_is_cpr_compatible(rb)) {
+        return;
+    }
+
+    error_setg(&rb->cpr_blocker,
+               "Memory region %s is not compatible with CPR. share=on is "
+               "required for memory-backend objects, and aux-ram-share=on is "
+               "required.", memory_region_name(rb->mr));
+    migrate_add_blocker_modes(&rb->cpr_blocker, errp, MIG_MODE_CPR_TRANSFER,
+                              -1);
+}
+
+void ram_block_del_cpr_blocker(RAMBlock *rb)
+{
+    migrate_del_blocker(&rb->cpr_blocker);
+}