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=-3.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 9ACCCC433E0 for ; Wed, 27 May 2020 04:21:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 78EE620B80 for ; Wed, 27 May 2020 04:21:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ozlabs.org header.i=@ozlabs.org header.b="Y+vOgomL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728796AbgE0EVG (ORCPT ); Wed, 27 May 2020 00:21:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728774AbgE0EVD (ORCPT ); Wed, 27 May 2020 00:21:03 -0400 Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73D7FC03E97B; Tue, 26 May 2020 21:21:03 -0700 (PDT) Received: by ozlabs.org (Postfix, from userid 1003) id 49WyLj3GH6z9sSn; Wed, 27 May 2020 14:21:01 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ozlabs.org; s=201707; t=1590553261; bh=LuXoMj6P54e5QxwVC+3xCxjAdWePyW9Cgdi4Q0bcS1k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Y+vOgomLr6ESV/IJP7UO0AaXuz/DuXxNtue37EXI8dBVu7nQizh6dPqM13DMY4Xot 2Q0a3sMEwLN2dZVj+YYn6wT65hE5ztVdWE5U3QsIzlO6NKWthROchj188cmcehgnLC 78E8ff33tvHuAaN8ovmpMXfU2JK0NyCN77HTz2NsQh8d3+elhTBehkDmXG+ZmPrasS RYyUDLxZH/7owlxyQJbCNUc+gUkjrgVGesWtgB+OmvpGx7qQIsVfPxyFdUmJBastdX PEupmA6lBUNmssjgyTfDWtyEob1mJX6LKewQVZoVp7dENIfz1hNnsshLIdnCg+kA8w phOvtndHgXIRw== Date: Wed, 27 May 2020 14:19:22 +1000 From: Paul Mackerras To: Qian Cai Cc: mpe@ellerman.id.au, benh@kernel.crashing.org, aik@ozlabs.ru, paulmck@kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] powerpc/kvm/book3s64/vio: fix some RCU-list locks Message-ID: <20200527041922.GE293451@thinks.paulus.ozlabs.org> References: <20200510051834.2011-1-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200510051834.2011-1-cai@lca.pw> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 10, 2020 at 01:18:34AM -0400, Qian Cai wrote: > It is unsafe to traverse kvm->arch.spapr_tce_tables and > stt->iommu_tables without the RCU read lock held. Also, add > cond_resched_rcu() in places with the RCU read lock held that could take > a while to finish. > > arch/powerpc/kvm/book3s_64_vio.c:76 RCU-list traversed in non-reader section!! > > other info that might help us debug this: > > rcu_scheduler_active = 2, debug_locks = 1 > no locks held by qemu-kvm/4265. > > stack backtrace: > CPU: 96 PID: 4265 Comm: qemu-kvm Not tainted 5.7.0-rc4-next-20200508+ #2 > Call Trace: > [c000201a8690f720] [c000000000715948] dump_stack+0xfc/0x174 (unreliable) > [c000201a8690f770] [c0000000001d9470] lockdep_rcu_suspicious+0x140/0x164 > [c000201a8690f7f0] [c008000010b9fb48] kvm_spapr_tce_release_iommu_group+0x1f0/0x220 [kvm] > [c000201a8690f870] [c008000010b8462c] kvm_spapr_tce_release_vfio_group+0x54/0xb0 [kvm] > [c000201a8690f8a0] [c008000010b84710] kvm_vfio_destroy+0x88/0x140 [kvm] > [c000201a8690f8f0] [c008000010b7d488] kvm_put_kvm+0x370/0x600 [kvm] > [c000201a8690f990] [c008000010b7e3c0] kvm_vm_release+0x38/0x60 [kvm] > [c000201a8690f9c0] [c0000000005223f4] __fput+0x124/0x330 > [c000201a8690fa20] [c000000000151cd8] task_work_run+0xb8/0x130 > [c000201a8690fa70] [c0000000001197e8] do_exit+0x4e8/0xfa0 > [c000201a8690fb70] [c00000000011a374] do_group_exit+0x64/0xd0 > [c000201a8690fbb0] [c000000000132c90] get_signal+0x1f0/0x1200 > [c000201a8690fcc0] [c000000000020690] do_notify_resume+0x130/0x3c0 > [c000201a8690fda0] [c000000000038d64] syscall_exit_prepare+0x1a4/0x280 > [c000201a8690fe20] [c00000000000c8f8] system_call_common+0xf8/0x278 > > ==== > arch/powerpc/kvm/book3s_64_vio.c:368 RCU-list traversed in non-reader section!! > > other info that might help us debug this: > > rcu_scheduler_active = 2, debug_locks = 1 > 2 locks held by qemu-kvm/4264: > #0: c000201ae2d000d8 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0xdc/0x950 [kvm] > #1: c000200c9ed0c468 (&kvm->srcu){....}-{0:0}, at: kvmppc_h_put_tce+0x88/0x340 [kvm] > > ==== > arch/powerpc/kvm/book3s_64_vio.c:108 RCU-list traversed in non-reader section!! > > other info that might help us debug this: > > rcu_scheduler_active = 2, debug_locks = 1 > 1 lock held by qemu-kvm/4257: > #0: c000200b1b363a40 (&kv->lock){+.+.}-{3:3}, at: kvm_vfio_set_attr+0x598/0x6c0 [kvm] > > ==== > arch/powerpc/kvm/book3s_64_vio.c:146 RCU-list traversed in non-reader section!! > > other info that might help us debug this: > > rcu_scheduler_active = 2, debug_locks = 1 > 1 lock held by qemu-kvm/4257: > #0: c000200b1b363a40 (&kv->lock){+.+.}-{3:3}, at: kvm_vfio_set_attr+0x598/0x6c0 [kvm] > > Signed-off-by: Qian Cai Thanks, applied to my kvm-ppc-next branch, with the cond_resched_rcu() in kvmppc_tce_validate removed. Paul.