The RAM save/restore code needs the RAMBlock in RAMBlockNotifier
callbacks to decide whether migration must be aborted and to update
RAMBlock state for postcopy. Looking up the RAMBlock inside callbacks is
hazardous: with Xen mapcache it can deadlock, and it also leaves the
callback contract unclear.

Pass the RAMBlock explicitly to RAMBlockNotifier callbacks. The
ram_block_resized callback takes a non-const RAMBlock because it may
modify the RAMBlock, while the other callbacks take const RAMBlock.

Xen mapcache passes NULL because mapcache entries do not have a
one-to-one relationship with RAMBlocks. ram_block_resized() is never
called from Xen mapcache, so its RAMBlock argument is always non-NULL.

Drop redundant parameters from ram_block_resized() because they can be
derived from the RAMBlock. Keep them for the other callbacks because
their RAMBlock argument may be NULL.

Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
---
 include/system/ramlist.h    | 18 ++++++++++--------
 block/block-ram-registrar.c |  8 ++++----
 hw/core/numa.c              | 18 ++++++++++--------
 hw/xen/xen-mapcache.c       |  6 +++---
 migration/ram.c             | 12 +++---------
 system/physmem.c            |  7 +++----
 target/i386/nvmm/nvmm-all.c |  4 ++--
 target/i386/sev.c           |  8 ++++----
 util/vfio-helpers.c         |  7 ++++---
 9 files changed, 43 insertions(+), 45 deletions(-)

diff --git a/include/system/ramlist.h b/include/system/ramlist.h
index c7f388f487d7..32157cc84305 100644
--- a/include/system/ramlist.h
+++ b/include/system/ramlist.h
@@ -62,11 +62,11 @@ void qemu_mutex_lock_ramlist(void);
 void qemu_mutex_unlock_ramlist(void);
 
 struct RAMBlockNotifier {
-    void (*ram_block_added)(RAMBlockNotifier *n, void *host, size_t size,
-                            size_t max_size);
-    void (*ram_block_removed)(RAMBlockNotifier *n, void *host, size_t size,
-                              size_t max_size);
-    void (*ram_block_resized)(RAMBlockNotifier *n, void *host, size_t old_size,
+    void (*ram_block_added)(RAMBlockNotifier *n, const RAMBlock *rb,
+                            void *host, size_t size, size_t max_size);
+    void (*ram_block_removed)(RAMBlockNotifier *n, const RAMBlock *rb,
+                              void *host, size_t size, size_t max_size);
+    void (*ram_block_resized)(RAMBlockNotifier *n, RAMBlock *rb,
                               size_t new_size);
     QLIST_ENTRY(RAMBlockNotifier) next;
 };
@@ -77,9 +77,11 @@ int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque);
 
 void ram_block_notifier_add(RAMBlockNotifier *n);
 void ram_block_notifier_remove(RAMBlockNotifier *n);
-void ram_block_notify_add(void *host, size_t size, size_t max_size);
-void ram_block_notify_remove(void *host, size_t size, size_t max_size);
-void ram_block_notify_resize(void *host, size_t old_size, size_t new_size);
+void ram_block_notify_add(const RAMBlock *rb,
+                          void *host, size_t size, size_t max_size);
+void ram_block_notify_remove(const RAMBlock *rb,
+                             void *host, size_t size, size_t max_size);
+void ram_block_notify_resize(RAMBlock *rb, size_t new_size);
 
 GString *ram_block_format(void);
 
diff --git a/block/block-ram-registrar.c b/block/block-ram-registrar.c
index fcda2b86afb2..5b938de22587 100644
--- a/block/block-ram-registrar.c
+++ b/block/block-ram-registrar.c
@@ -9,8 +9,8 @@
 #include "system/block-ram-registrar.h"
 #include "qapi/error.h"
 
-static void ram_block_added(RAMBlockNotifier *n, void *host, size_t size,
-                            size_t max_size)
+static void ram_block_added(RAMBlockNotifier *n, const RAMBlock *rb,
+                            void *host, size_t size, size_t max_size)
 {
     BlockRAMRegistrar *r = container_of(n, BlockRAMRegistrar, notifier);
     Error *err = NULL;
@@ -26,8 +26,8 @@ static void ram_block_added(RAMBlockNotifier *n, void *host, size_t size,
     }
 }
 
-static void ram_block_removed(RAMBlockNotifier *n, void *host, size_t size,
-                              size_t max_size)
+static void ram_block_removed(RAMBlockNotifier *n, const RAMBlock *rb,
+                              void *host, size_t size, size_t max_size)
 {
     BlockRAMRegistrar *r = container_of(n, BlockRAMRegistrar, notifier);
     blk_unregister_buf(r->blk, host, max_size);
diff --git a/hw/core/numa.c b/hw/core/numa.c
index f462883c87cf..40acb98bdd0b 100644
--- a/hw/core/numa.c
+++ b/hw/core/numa.c
@@ -824,7 +824,7 @@ static int ram_block_notify_add_single(RAMBlock *rb, void *opaque)
     RAMBlockNotifier *notifier = opaque;
 
     if (host) {
-        notifier->ram_block_added(notifier, host, size, max_size);
+        notifier->ram_block_added(notifier, rb, host, size, max_size);
     }
     return 0;
 }
@@ -837,7 +837,7 @@ static int ram_block_notify_remove_single(RAMBlock *rb, void *opaque)
     RAMBlockNotifier *notifier = opaque;
 
     if (host) {
-        notifier->ram_block_removed(notifier, host, size, max_size);
+        notifier->ram_block_removed(notifier, rb, host, size, max_size);
     }
     return 0;
 }
@@ -861,38 +861,40 @@ void ram_block_notifier_remove(RAMBlockNotifier *n)
     }
 }
 
-void ram_block_notify_add(void *host, size_t size, size_t max_size)
+void ram_block_notify_add(const RAMBlock *rb,
+                          void *host, size_t size, size_t max_size)
 {
     RAMBlockNotifier *notifier;
     RAMBlockNotifier *next;
 
     QLIST_FOREACH_SAFE(notifier, &ram_list.ramblock_notifiers, next, next) {
         if (notifier->ram_block_added) {
-            notifier->ram_block_added(notifier, host, size, max_size);
+            notifier->ram_block_added(notifier, rb, host, size, max_size);
         }
     }
 }
 
-void ram_block_notify_remove(void *host, size_t size, size_t max_size)
+void ram_block_notify_remove(const RAMBlock *rb,
+                             void *host, size_t size, size_t max_size)
 {
     RAMBlockNotifier *notifier;
     RAMBlockNotifier *next;
 
     QLIST_FOREACH_SAFE(notifier, &ram_list.ramblock_notifiers, next, next) {
         if (notifier->ram_block_removed) {
-            notifier->ram_block_removed(notifier, host, size, max_size);
+            notifier->ram_block_removed(notifier, rb, host, size, max_size);
         }
     }
 }
 
-void ram_block_notify_resize(void *host, size_t old_size, size_t new_size)
+void ram_block_notify_resize(RAMBlock *rb, size_t new_size)
 {
     RAMBlockNotifier *notifier;
     RAMBlockNotifier *next;
 
     QLIST_FOREACH_SAFE(notifier, &ram_list.ramblock_notifiers, next, next) {
         if (notifier->ram_block_resized) {
-            notifier->ram_block_resized(notifier, host, old_size, new_size);
+            notifier->ram_block_resized(notifier, rb, new_size);
         }
     }
 }
diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
index 85cf0cf359ca..f321c65b630e 100644
--- a/hw/xen/xen-mapcache.c
+++ b/hw/xen/xen-mapcache.c
@@ -222,7 +222,7 @@ static void xen_remap_bucket(MapCache *mc,
 
     if (entry->vaddr_base != NULL) {
         if (!(entry->flags & XEN_MAPCACHE_ENTRY_DUMMY)) {
-            ram_block_notify_remove(entry->vaddr_base, entry->size,
+            ram_block_notify_remove(NULL, entry->vaddr_base, entry->size,
                                     entry->size);
         }
 
@@ -308,7 +308,7 @@ static void xen_remap_bucket(MapCache *mc,
     }
 
     if (!(entry->flags & XEN_MAPCACHE_ENTRY_DUMMY)) {
-        ram_block_notify_add(vaddr_base, size, size);
+        ram_block_notify_add(NULL, vaddr_base, size, size);
     }
 
     entry->vaddr_base = vaddr_base;
@@ -601,7 +601,7 @@ static void xen_invalidate_map_cache_entry_unlocked(MapCache *mc,
         return;
     }
 
-    ram_block_notify_remove(entry->vaddr_base, entry->size, entry->size);
+    ram_block_notify_remove(NULL, entry->vaddr_base, entry->size, entry->size);
     if (entry->flags & XEN_MAPCACHE_ENTRY_GRANT) {
         rc = xengnttab_unmap(xen_region_gnttabdev, entry->vaddr_base,
                              entry->size >> mc->bucket_shift);
diff --git a/migration/ram.c b/migration/ram.c
index fc38ffbf8af1..6bc7f705d31a 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4699,18 +4699,12 @@ static SaveVMHandlers savevm_ram_handlers = {
     .save_postcopy_prepare = ram_save_postcopy_prepare,
 };
 
-static void ram_mig_ram_block_resized(RAMBlockNotifier *n, void *host,
-                                      size_t old_size, size_t new_size)
+static void ram_mig_ram_block_resized(RAMBlockNotifier *n, RAMBlock *rb,
+                                      size_t new_size)
 {
     PostcopyState ps = postcopy_state_get();
-    ram_addr_t offset;
-    RAMBlock *rb = qemu_ram_block_from_host(host, false, &offset);
     Error *err = NULL;
-
-    if (!rb) {
-        error_report("RAM block not found");
-        return;
-    }
+    ram_addr_t old_size = qemu_ram_get_used_length(rb);
 
     if (migrate_ram_is_ignored(rb)) {
         return;
diff --git a/system/physmem.c b/system/physmem.c
index 54fe820ce828..1427949b72cd 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2019,7 +2019,6 @@ static int memory_try_enable_merging(void *addr, size_t len)
  */
 int qemu_ram_resize(RAMBlock *block, ram_addr_t newsize, Error **errp)
 {
-    const ram_addr_t oldsize = block->used_length;
     const ram_addr_t unaligned_size = newsize;
 
     newsize = TARGET_PAGE_ALIGN(newsize);
@@ -2054,7 +2053,7 @@ int qemu_ram_resize(RAMBlock *block, ram_addr_t newsize, Error **errp)
 
     /* Notify before modifying the ram block and touching the bitmaps. */
     if (block->host) {
-        ram_block_notify_resize(block->host, oldsize, newsize);
+        ram_block_notify_resize(block, newsize);
     }
 
     physical_memory_clear_dirty_range(block->offset, block->used_length);
@@ -2277,7 +2276,7 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
             qemu_madvise(new_block->host, new_block->max_length,
                          QEMU_MADV_DONTFORK);
         }
-        ram_block_notify_add(new_block->host, new_block->used_length,
+        ram_block_notify_add(new_block, new_block->host, new_block->used_length,
                              new_block->max_length);
     }
     return;
@@ -2588,7 +2587,7 @@ void qemu_ram_free(RAMBlock *block)
     }
 
     if (block->host) {
-        ram_block_notify_remove(block->host, block->used_length,
+        ram_block_notify_remove(block, block->host, block->used_length,
                                 block->max_length);
     }
 
diff --git a/target/i386/nvmm/nvmm-all.c b/target/i386/nvmm/nvmm-all.c
index 8a1af35ed32b..f29b9c504ea8 100644
--- a/target/i386/nvmm/nvmm-all.c
+++ b/target/i386/nvmm/nvmm-all.c
@@ -1134,8 +1134,8 @@ static MemoryListener nvmm_memory_listener = {
 };
 
 static void
-nvmm_ram_block_added(RAMBlockNotifier *n, void *host, size_t size,
-                     size_t max_size)
+nvmm_ram_block_added(RAMBlockNotifier *n, const RAMBlock *rb,
+                     void *host, size_t size, size_t max_size)
 {
     struct nvmm_machine *mach = get_nvmm_mach();
     uintptr_t hva = (uintptr_t)host;
diff --git a/target/i386/sev.c b/target/i386/sev.c
index 99cf30806be7..55e74f1c8f9c 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -329,8 +329,8 @@ sev_set_guest_state(SevCommonState *sev_common, SevState new_state)
 }
 
 static void
-sev_ram_block_added(RAMBlockNotifier *n, void *host, size_t size,
-                    size_t max_size)
+sev_ram_block_added(RAMBlockNotifier *n, const RAMBlock *rb,
+                    void *host, size_t size, size_t max_size)
 {
     int r;
     struct kvm_enc_region range;
@@ -359,8 +359,8 @@ sev_ram_block_added(RAMBlockNotifier *n, void *host, size_t size,
 }
 
 static void
-sev_ram_block_removed(RAMBlockNotifier *n, void *host, size_t size,
-                      size_t max_size)
+sev_ram_block_removed(RAMBlockNotifier *n, const RAMBlock *rb,
+                      void *host, size_t size, size_t max_size)
 {
     int r;
     struct kvm_enc_region range;
diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
index aab0bf9d485d..5059ed44b8af 100644
--- a/util/vfio-helpers.c
+++ b/util/vfio-helpers.c
@@ -465,8 +465,8 @@ fail_container:
     return ret;
 }
 
-static void qemu_vfio_ram_block_added(RAMBlockNotifier *n, void *host,
-                                      size_t size, size_t max_size)
+static void qemu_vfio_ram_block_added(RAMBlockNotifier *n, const RAMBlock *rb,
+                                      void *host, size_t size, size_t max_size)
 {
     QEMUVFIOState *s = container_of(n, QEMUVFIOState, ram_notifier);
     Error *local_err = NULL;
@@ -481,7 +481,8 @@ static void qemu_vfio_ram_block_added(RAMBlockNotifier *n, void *host,
     }
 }
 
-static void qemu_vfio_ram_block_removed(RAMBlockNotifier *n, void *host,
+static void qemu_vfio_ram_block_removed(RAMBlockNotifier *n, const RAMBlock *rb,
+                                        void *host,
                                         size_t size, size_t max_size)
 {
     QEMUVFIOState *s = container_of(n, QEMUVFIOState, ram_notifier);

-- 
2.54.0