From 59bcc049c17a50d8ac0353f164f597e7d904589d Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Thu, 5 Jan 2023 13:45:27 +0100 Subject: [PATCH] migration/ram: Rely on used_length for uffd_change_protection() ram_mig_ram_block_resized() will abort migration (including background snapshots) when resizing a RAMBlock. ram_block_populate_read() will only populate RAM up to used_length, so at least for anonymous memory protecting everything between used_length and max_length won't actually be protected and is just a NOP. So let's only protect everything up to used_length. Note: it still makes sense to register uffd-wp for max_length, such that RAM_UF_WRITEPROTECT is independent of a changing used_length. Reviewed-by: Peter Xu Reviewed-by: Juan Quintela Signed-off-by: David Hildenbrand Signed-off-by: Juan Quintela --- migration/ram.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/migration/ram.c b/migration/ram.c index efaae07dd8..a6956c9e7d 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1901,7 +1901,7 @@ int ram_write_tracking_start(void) /* Apply UFFD write protection to the block memory range */ if (uffd_change_protection(rs->uffdio_fd, block->host, - block->max_length, true, false)) { + block->used_length, true, false)) { goto fail; }