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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 47225C28D15 for ; Tue, 2 Mar 2021 06:39:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0FA3861601 for ; Tue, 2 Mar 2021 06:39:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1573161AbhCBDTc (ORCPT ); Mon, 1 Mar 2021 22:19:32 -0500 Received: from mail.kernel.org ([198.145.29.99]:48282 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243301AbhCAUXt (ORCPT ); Mon, 1 Mar 2021 15:23:49 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id EB401653FB; Mon, 1 Mar 2021 18:05:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614621912; bh=jndP/atYEx1DXAoD9+8u6UWOuQz+iYeZGp1liYsxr4Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tzi6M6Lk45WWvJh8MWuRcV7PigD6cFFEvT142jqyzU76o4p28vcZegXlcE8DaEUm5 LtwOwoR8dftHpXvfO4f8a4CZpnCUp66ZHuf1DG3T+TTGm9apEFlYzMv4U+CzBYDN6O AhpEmQXLe0ESiQ6bMOvIashfcZUaIfGYFW+HzlJ0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mark Rutland , Lorenzo Pieralisi , Peter Zijlstra , Boqun Feng , Marc Zyngier , Saravana Kannan , "Paul E . McKenney" , Sami Tolvanen , Will Deacon Subject: [PATCH 5.11 688/775] arm64: spectre: Prevent lockdep splat on v4 mitigation enable path Date: Mon, 1 Mar 2021 17:14:16 +0100 Message-Id: <20210301161235.384895940@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210301161201.679371205@linuxfoundation.org> References: <20210301161201.679371205@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Will Deacon commit a2c42bbabbe260b7626d8459093631a6e16ee0ee upstream. The Spectre-v4 workaround is re-configured when resuming from suspend, as the firmware may have re-enabled the mitigation despite the user previously asking for it to be disabled. Enabling or disabling the workaround can result in an undefined instruction exception on CPUs which implement PSTATE.SSBS but only allow it to be configured by adjusting the SPSR on exception return. We handle this by installing an 'undef hook' which effectively emulates the access. Installing this hook requires us to take a couple of spinlocks both to avoid corrupting the internal list of hooks but also to ensure that we don't run into an unhandled exception. Unfortunately, when resuming from suspend, we haven't yet called rcu_idle_exit() and so lockdep gets angry about "suspicious RCU usage". In doing so, it tries to print a warning, which leads it to get even more suspicious, this time about itself: | rcu_scheduler_active = 2, debug_locks = 1 | RCU used illegally from extended quiescent state! | 1 lock held by swapper/0: | #0: (logbuf_lock){-.-.}-{2:2}, at: vprintk_emit+0x88/0x198 | | Call trace: | dump_backtrace+0x0/0x1d8 | show_stack+0x18/0x24 | dump_stack+0xe0/0x17c | lockdep_rcu_suspicious+0x11c/0x134 | trace_lock_release+0xa0/0x160 | lock_release+0x3c/0x290 | _raw_spin_unlock+0x44/0x80 | vprintk_emit+0xbc/0x198 | vprintk_default+0x44/0x6c | vprintk_func+0x1f4/0x1fc | printk+0x54/0x7c | lockdep_rcu_suspicious+0x30/0x134 | trace_lock_acquire+0xa0/0x188 | lock_acquire+0x50/0x2fc | _raw_spin_lock+0x68/0x80 | spectre_v4_enable_mitigation+0xa8/0x30c | __cpu_suspend_exit+0xd4/0x1a8 | cpu_suspend+0xa0/0x104 | psci_cpu_suspend_enter+0x3c/0x5c | psci_enter_idle_state+0x44/0x74 | cpuidle_enter_state+0x148/0x2f8 | cpuidle_enter+0x38/0x50 | do_idle+0x1f0/0x2b4 Prevent these splats by running __cpu_suspend_exit() with RCU watching. Cc: Mark Rutland Cc: Lorenzo Pieralisi Cc: Peter Zijlstra Cc: Boqun Feng Cc: Marc Zyngier Cc: Saravana Kannan Suggested-by: "Paul E . McKenney" Reported-by: Sami Tolvanen Fixes: c28762070ca6 ("arm64: Rewrite Spectre-v4 mitigation code") Cc: Acked-by: Paul E. McKenney Acked-by: Marc Zyngier Acked-by: Mark Rutland Link: https://lore.kernel.org/r/20210218140346.5224-1-will@kernel.org Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/suspend.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/arm64/kernel/suspend.c +++ b/arch/arm64/kernel/suspend.c @@ -119,7 +119,7 @@ int cpu_suspend(unsigned long arg, int ( if (!ret) ret = -EOPNOTSUPP; } else { - __cpu_suspend_exit(); + RCU_NONIDLE(__cpu_suspend_exit()); } unpause_graph_tracing();