[V2,06/11] migration: fix mismatched GPAs during cpr

Commit Message

Steve Sistare June 30, 2024, 7:40 p.m. UTC

For new cpr modes, ramblock_is_ignored will always be true, because the
memory is preserved in place rather than copied.  However, for an ignored
block, parse_ramblock currently requires that the received address of the
block must match the address of the statically initialized region on the
target.  This fails for a PCI rom block, because the memory region address
is set when the guest writes to a BAR on the source, which does not occur
on the target, causing a "Mismatched GPAs" error during cpr migration.

To fix, unconditionally set the target's address to the source's address
if the target region does not have an address yet.

Signed-off-by: Steve Sistare <[e-mail]>
Reviewed-by: Fabiano Rosas <[e-mail]>
---
 include/exec/memory.h | 12 ++++++++++++
 migration/ram.c       | 15 +++++++++------
 system/memory.c       | 10 ++++++++--
 3 files changed, 29 insertions(+), 8 deletions(-)

Patch

diff --git a/include/exec/memory.h b/include/exec/memory.h
index c26ede3..227169e 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -811,6 +811,7 @@  struct MemoryRegion {
     bool ram_device;
     bool enabled;
     bool warning_printed; /* For reservations */
+    bool has_addr;
     uint8_t vga_logging_count;
     MemoryRegion *alias;
     hwaddr alias_offset;
@@ -2408,6 +2409,17 @@  void memory_region_set_enabled(MemoryRegion *mr, bool enabled);
 void memory_region_set_address(MemoryRegion *mr, hwaddr addr);
 
 /*
+ * memory_region_set_address_only: set the address of a region.
+ *
+ * Same as memory_region_set_address, but without causing transaction side
+ * effects.
+ *
+ * @mr: the region to be updated
+ * @addr: new address, relative to container region
+ */
+void memory_region_set_address_only(MemoryRegion *mr, hwaddr addr);
+
+/*
  * memory_region_set_size: dynamically update the size of a region.
  *
  * Dynamically updates the size of a region.
diff --git a/migration/ram.c b/migration/ram.c
index edec1a2..eaf3151 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4059,12 +4059,15 @@  static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
     }
     if (migrate_ignore_shared()) {
         hwaddr addr = qemu_get_be64(f);
-        if (migrate_ram_is_ignored(block) &&
-            block->mr->addr != addr) {
-            error_report("Mismatched GPAs for block %s "
-                         "%" PRId64 "!= %" PRId64, block->idstr,
-                         (uint64_t)addr, (uint64_t)block->mr->addr);
-            return -EINVAL;
+        if (migrate_ram_is_ignored(block)) {
+            if (!block->mr->has_addr) {
+                memory_region_set_address_only(block->mr, addr);
+            } else if (block->mr->addr != addr) {
+                error_report("Mismatched GPAs for block %s "
+                             "%" PRId64 "!= %" PRId64, block->idstr,
+                             (uint64_t)addr, (uint64_t)block->mr->addr);
+                return -EINVAL;
+            }
         }
     }
     ret = rdma_block_notification_handle(f, block->idstr);
diff --git a/system/memory.c b/system/memory.c
index 28a837d..b7548bf 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -2655,7 +2655,7 @@  static void memory_region_add_subregion_common(MemoryRegion *mr,
     for (alias = subregion->alias; alias; alias = alias->alias) {
         alias->mapped_via_alias++;
     }
-    subregion->addr = offset;
+    memory_region_set_address_only(subregion, offset);
     memory_region_update_container_subregions(subregion);
 }
 
@@ -2735,10 +2735,16 @@  static void memory_region_readd_subregion(MemoryRegion *mr)
     }
 }
 
+void memory_region_set_address_only(MemoryRegion *mr, hwaddr addr)
+{
+    mr->addr = addr;
+    mr->has_addr = true;
+}
+
 void memory_region_set_address(MemoryRegion *mr, hwaddr addr)
 {
     if (addr != mr->addr) {
-        mr->addr = addr;
+        memory_region_set_address_only(mr, addr);
         memory_region_readd_subregion(mr);
     }
 }