Firstly, renaming the old matching_page_sizes variable to matching_target_page_size, which suites more to what it did (it only checks against target page size rather than multiple page sizes). Meanwhile, simplify the check logic a bit, and enhance the comments. Should have no functional change.
Signed-off-by: Peter Xu <pet...@redhat.com> --- migration/ram.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/migration/ram.c b/migration/ram.c index 23cea47090..fbeb23f750 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -3580,7 +3580,7 @@ static int ram_load_postcopy(QEMUFile *f) { int flags = 0, ret = 0; bool place_needed = false; - bool matching_page_sizes = false; + bool matching_target_page_size = false; MigrationIncomingState *mis = migration_incoming_get_current(); /* Temporary page that is later 'placed' */ void *postcopy_host_page = postcopy_get_tmp_page(mis); @@ -3620,7 +3620,7 @@ static int ram_load_postcopy(QEMUFile *f) ret = -EINVAL; break; } - matching_page_sizes = block->page_size == TARGET_PAGE_SIZE; + matching_target_page_size = block->page_size == TARGET_PAGE_SIZE; /* * Postcopy requires that we place whole host pages atomically; * these may be huge pages for RAMBlocks that are backed by @@ -3668,12 +3668,17 @@ static int ram_load_postcopy(QEMUFile *f) case RAM_SAVE_FLAG_PAGE: all_zero = false; - if (!place_needed || !matching_page_sizes) { + if (!matching_target_page_size) { + /* For huge pages, we always use temporary buffer */ qemu_get_buffer(f, page_buffer, TARGET_PAGE_SIZE); } else { - /* Avoids the qemu_file copy during postcopy, which is - * going to do a copy later; can only do it when we - * do this read in one go (matching page sizes) + /* + * For small pages that matches target page size, we + * avoid the qemu_file copy. Instead we directly use + * the buffer of QEMUFile to place the page. Note: we + * cannot do any QEMUFile operation before using that + * buffer to make sure the buffer is valid when + * placing the page. */ qemu_get_buffer_in_place(f, (uint8_t **)&place_source, TARGET_PAGE_SIZE); -- 2.17.1