From patchwork Tue Sep 17 18:10:45 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 13806401 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 440E6CAC594 for ; Tue, 17 Sep 2024 18:11:38 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sqcfY-0007cQ-3m; Tue, 17 Sep 2024 14:11:20 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sqcfS-0006yd-Ka; Tue, 17 Sep 2024 14:11:15 -0400 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sqcfQ-0002hI-PS; Tue, 17 Sep 2024 14:11:14 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id CBECC8FBDC; Tue, 17 Sep 2024 21:10:51 +0300 (MSK) Received: from think4mjt.tls.msk.ru (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id 0BA5613E753; Tue, 17 Sep 2024 21:11:06 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, David Hildenbrand , Peter Maydell , Stefan Hajnoczi , Peter Xu , Paolo Bonzini , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , Michael Tokarev Subject: [Stable-8.2.7 56/65] softmmu/physmem: fix memory leak in dirty_memory_extend() Date: Tue, 17 Sep 2024 21:10:45 +0300 Message-Id: <20240917181054.633974-4-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: David Hildenbrand As reported by Peter, we might be leaking memory when removing the highest RAMBlock (in the weird ram_addr_t space), and adding a new one. We will fail to realize that we already allocated bitmaps for more dirty memory blocks, and effectively discard the pointers to them. Fix it by getting rid of last_ram_page() and by remembering the number of dirty memory blocks that have been allocated already. While at it, let's use "unsigned int" for the number of blocks, which should be sufficient until we reach ~32 exabytes. Looks like this leak was introduced as we switched from using a single bitmap_zero_extend() to allocating multiple bitmaps: bitmap_zero_extend() relies on g_renew() which should have taken care of this. Resolves: https://lkml.kernel.org/r/CAFEAcA-k7a+VObGAfCFNygQNfCKL=AfX6A4kScq=VSSK0peqPg@mail.gmail.com Reported-by: Peter Maydell Fixes: 5b82b703b69a ("memory: RCU ram_list.dirty_memory[] for safe RAM hotplug") Reviewed-by: Stefan Hajnoczi Reviewed-by: Peter Xu Tested-by: Peter Maydell Cc: qemu-stable@nongnu.org Cc: Stefan Hajnoczi Cc: Paolo Bonzini Cc: Peter Xu Cc: Philippe Mathieu-Daudé Signed-off-by: David Hildenbrand Link: https://lore.kernel.org/r/20240828090743.128647-1-david@redhat.com Signed-off-by: Peter Xu (cherry picked from commit b84f06c2bee727b3870b4eeccbe3a45c5aea14c1) Signed-off-by: Michael Tokarev (Mjt: context fix due to lack of v9.0.0-rc4-49-g15f7a80c49cb "RAMBlock: Add support of KVM private guest memfd") diff --git a/include/exec/ramlist.h b/include/exec/ramlist.h index 2ad2a81acc..d9cfe530be 100644 --- a/include/exec/ramlist.h +++ b/include/exec/ramlist.h @@ -50,6 +50,7 @@ typedef struct RAMList { /* RCU-enabled, writes protected by the ramlist lock. */ QLIST_HEAD(, RAMBlock) blocks; DirtyMemoryBlocks *dirty_memory[DIRTY_MEMORY_NUM]; + unsigned int num_dirty_blocks; uint32_t version; QLIST_HEAD(, RAMBlockNotifier) ramblock_notifiers; } RAMList; diff --git a/system/physmem.c b/system/physmem.c index a63853a7bc..073e6c6124 100644 --- a/system/physmem.c +++ b/system/physmem.c @@ -1499,18 +1499,6 @@ static ram_addr_t find_ram_offset(ram_addr_t size) return offset; } -static unsigned long last_ram_page(void) -{ - RAMBlock *block; - ram_addr_t last = 0; - - RCU_READ_LOCK_GUARD(); - RAMBLOCK_FOREACH(block) { - last = MAX(last, block->offset + block->max_length); - } - return last >> TARGET_PAGE_BITS; -} - static void qemu_ram_setup_dump(void *addr, ram_addr_t size) { int ret; @@ -1763,13 +1751,11 @@ void qemu_ram_msync(RAMBlock *block, ram_addr_t start, ram_addr_t length) } /* Called with ram_list.mutex held */ -static void dirty_memory_extend(ram_addr_t old_ram_size, - ram_addr_t new_ram_size) +static void dirty_memory_extend(ram_addr_t new_ram_size) { - ram_addr_t old_num_blocks = DIV_ROUND_UP(old_ram_size, - DIRTY_MEMORY_BLOCK_SIZE); - ram_addr_t new_num_blocks = DIV_ROUND_UP(new_ram_size, - DIRTY_MEMORY_BLOCK_SIZE); + unsigned int old_num_blocks = ram_list.num_dirty_blocks; + unsigned int new_num_blocks = DIV_ROUND_UP(new_ram_size, + DIRTY_MEMORY_BLOCK_SIZE); int i; /* Only need to extend if block count increased */ @@ -1801,6 +1787,8 @@ static void dirty_memory_extend(ram_addr_t old_ram_size, g_free_rcu(old_blocks, rcu); } } + + ram_list.num_dirty_blocks = new_num_blocks; } static void ram_block_add(RAMBlock *new_block, Error **errp) @@ -1809,11 +1797,9 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) const bool shared = qemu_ram_is_shared(new_block); RAMBlock *block; RAMBlock *last_block = NULL; - ram_addr_t old_ram_size, new_ram_size; + ram_addr_t ram_size; Error *err = NULL; - old_ram_size = last_ram_page(); - qemu_mutex_lock_ramlist(); new_block->offset = find_ram_offset(new_block->max_length); @@ -1841,11 +1827,8 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) } } - new_ram_size = MAX(old_ram_size, - (new_block->offset + new_block->max_length) >> TARGET_PAGE_BITS); - if (new_ram_size > old_ram_size) { - dirty_memory_extend(old_ram_size, new_ram_size); - } + ram_size = (new_block->offset + new_block->max_length) >> TARGET_PAGE_BITS; + dirty_memory_extend(ram_size); /* Keep the list sorted from biggest to smallest block. Unlike QTAILQ, * QLIST (which has an RCU-friendly variant) does not have insertion at * tail, so save the last element in last_block.