static int ram_load_postcopy(QEMUFile *f) { int flags = 0, ret = 0; bool place_needed = false; bool matching_page_sizes = qemu_host_page_size == TARGET_PAGE_SIZE; MigrationIncomingState *mis = migration_incoming_get_current(); /* Temporary page that is later 'placed' */ void *postcopy_host_page = postcopy_get_tmp_page(mis); void *last_host = NULL; bool all_zero = false; while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) { ram_addr_t addr; void *host = NULL; void *page_buffer = NULL; void *place_source = NULL; uint8_t ch; addr = qemu_get_be64(f); flags = addr & ~TARGET_PAGE_MASK; addr &= TARGET_PAGE_MASK; trace_ram_load_postcopy_loop((uint64_t)addr, flags); place_needed = false; if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE)) { host = host_from_stream_offset(f, addr, flags); if (!host) { error_report("Illegal RAM offset " RAM_ADDR_FMT, addr); ret = -EINVAL; break; } page_buffer = host; /* * Postcopy requires that we place whole host pages atomically. * To make it atomic, the data is read into a temporary page * that's moved into place later. * The migration protocol uses, possibly smaller, target-pages * however the source ensures it always sends all the components * of a host page in order. */ page_buffer = postcopy_host_page + ((uintptr_t)host & ~qemu_host_page_mask); /* If all TP are zero then we can optimise the place */ if (!((uintptr_t)host & ~qemu_host_page_mask)) { all_zero = true; } else { /* not the 1st TP within the HP */ if (host != (last_host + TARGET_PAGE_SIZE)) { error_report("Non-sequential target page %p/%p", host, last_host); ret = -EINVAL; break; } } /* * If it's the last part of a host page then we place the host * page */ place_needed = (((uintptr_t)host + TARGET_PAGE_SIZE) & ~qemu_host_page_mask) == 0; place_source = postcopy_host_page; } last_host = host; switch (flags & ~RAM_SAVE_FLAG_CONTINUE) { case RAM_SAVE_FLAG_COMPRESS: ch = qemu_get_byte(f); memset(page_buffer, ch, TARGET_PAGE_SIZE); if (ch) { all_zero = false; } break; case RAM_SAVE_FLAG_PAGE: all_zero = false; if (!place_needed || !matching_page_sizes) { 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) */ qemu_get_buffer_in_place(f, (uint8_t **)&place_source, TARGET_PAGE_SIZE); } break; case RAM_SAVE_FLAG_EOS: /* normal exit */ break; default: error_report("Unknown combination of migration flags: %#x" " (postcopy mode)", flags); ret = -EINVAL; } if (place_needed) { /* This gets called at the last target page in the host page */ if (all_zero) { ret = postcopy_place_page_zero(mis, host + TARGET_PAGE_SIZE - qemu_host_page_size); } else { ret = postcopy_place_page(mis, host + TARGET_PAGE_SIZE - qemu_host_page_size, place_source); } } if (!ret) { ret = qemu_file_get_error(f); } } return ret; }