[Qemu-devel] [PATCH 01/15] postcopy: Transmit and compare individual page sizes

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

When using postcopy with hugepages, we require the source
and destination page sizes for any RAMBlock to match.

Transmit them as part of the RAM information header and
fail if there's a difference.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/ram.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/migration/ram.c b/migration/ram.c
index a1c8089..39998f5 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1970,6 +1970,9 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
         qemu_put_byte(f, strlen(block->idstr));
         qemu_put_buffer(f, (uint8_t *)block->idstr, strlen(block->idstr));
         qemu_put_be64(f, block->used_length);
+        if (migrate_postcopy_ram() && block->page_size != qemu_host_page_size) {
+            qemu_put_be64(f, block->page_size);
+        }
     }
 
     rcu_read_unlock();
@@ -2536,6 +2539,18 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
                             error_report_err(local_err);
                         }
                     }
+                    /* For postcopy we need to check hugepage sizes match */
+                    if (migrate_postcopy_ram() &&
+                        block->page_size != qemu_host_page_size) {
+                        uint64_t remote_page_size = qemu_get_be64(f);
+                        if (remote_page_size != block->page_size) {
+                            error_report("Mismatched RAM page size %s "
+                                         "(local) %" PRId64 "!= %" PRId64,
+                                         id, block->page_size,
+                                         remote_page_size);
+                            ret = -EINVAL;
+                        }
+                    }
                     ram_control_load_hook(f, RAM_CONTROL_BLOCK_REG,
                                           block->idstr);
                 } else {
-- 
2.9.3