From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79B4CC433ED for ; Wed, 5 May 2021 17:21:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 46E6D613D8 for ; Wed, 5 May 2021 17:21:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240122AbhEERUV (ORCPT ); Wed, 5 May 2021 13:20:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:60884 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237696AbhEEREN (ORCPT ); Wed, 5 May 2021 13:04:13 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D6BAA61443; Wed, 5 May 2021 16:41:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1620232920; bh=+poiMp1CCkudZcpCIYkL5qXhzCYiNn29AWYI8h13T+8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cun3ucXux19BQOuHJLgMXdfRA0fBM3axCootVJQdlT+D8D1J1D1Hqj+vWK9DyeuAk h7IhkXjlTARzyr1wAn/cltw9uY2F9GxH5eKJn2J7Bx5jYWm3nIjz3M2EA1yqDl1i3T oYOt4al/abHJAoTSBZXx9ccxEqWrBlFORJoruAGyM9WbYReYRbGO6jBKwJ1LaTspVd SzIomoQVVJM0VVhSCR/GkuIJjFnYfiKkiDYL+4fB7PonfIliXWUB5bJb0WWlS436Pp byvaDUE5bdlWije/ktU1gFo5tnR0ggCdB1G22hQubOOFQrfgtMY5pAGNeEai+sVwG2 k0Wr5BvylXAVg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Alexey Kardashevskiy , Michael Ellerman , Sasha Levin , linuxppc-dev@lists.ozlabs.org Subject: [PATCH AUTOSEL 4.9 21/22] powerpc/iommu: Annotate nested lock for lockdep Date: Wed, 5 May 2021 12:41:28 -0400 Message-Id: <20210505164129.3464277-21-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210505164129.3464277-1-sashal@kernel.org> References: <20210505164129.3464277-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alexey Kardashevskiy [ Upstream commit cc7130bf119add37f36238343a593b71ef6ecc1e ] The IOMMU table is divided into pools for concurrent mappings and each pool has a separate spinlock. When taking the ownership of an IOMMU group to pass through a device to a VM, we lock these spinlocks which triggers a false negative warning in lockdep (below). This fixes it by annotating the large pool's spinlock as a nest lock which makes lockdep not complaining when locking nested locks if the nest lock is locked already. === WARNING: possible recursive locking detected 5.11.0-le_syzkaller_a+fstn1 #100 Not tainted -------------------------------------------- qemu-system-ppc/4129 is trying to acquire lock: c0000000119bddb0 (&(p->lock)/1){....}-{2:2}, at: iommu_take_ownership+0xac/0x1e0 but task is already holding lock: c0000000119bdd30 (&(p->lock)/1){....}-{2:2}, at: iommu_take_ownership+0xac/0x1e0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(p->lock)/1); lock(&(p->lock)/1); === Signed-off-by: Alexey Kardashevskiy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210301063653.51003-1-aik@ozlabs.ru Signed-off-by: Sasha Levin --- arch/powerpc/kernel/iommu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c index 9bfdd2510fd5..2cf900d16527 100644 --- a/arch/powerpc/kernel/iommu.c +++ b/arch/powerpc/kernel/iommu.c @@ -1021,7 +1021,7 @@ int iommu_take_ownership(struct iommu_table *tbl) spin_lock_irqsave(&tbl->large_pool.lock, flags); for (i = 0; i < tbl->nr_pools; i++) - spin_lock(&tbl->pools[i].lock); + spin_lock_nest_lock(&tbl->pools[i].lock, &tbl->large_pool.lock); if (tbl->it_offset == 0) clear_bit(0, tbl->it_map); @@ -1050,7 +1050,7 @@ void iommu_release_ownership(struct iommu_table *tbl) spin_lock_irqsave(&tbl->large_pool.lock, flags); for (i = 0; i < tbl->nr_pools; i++) - spin_lock(&tbl->pools[i].lock); + spin_lock_nest_lock(&tbl->pools[i].lock, &tbl->large_pool.lock); memset(tbl->it_map, 0, sz); -- 2.30.2