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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 517E2C7618A for ; Wed, 15 Mar 2023 12:44:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233120AbjCOMoP (ORCPT ); Wed, 15 Mar 2023 08:44:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232984AbjCOMn5 (ORCPT ); Wed, 15 Mar 2023 08:43:57 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84D5EA4B3C for ; Wed, 15 Mar 2023 05:42:40 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 5E1BAB81E05 for ; Wed, 15 Mar 2023 12:42:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB874C4339B; Wed, 15 Mar 2023 12:42:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1678884155; bh=XXhWnAJ1mPexiyOnY6ivwMe4/AfJL2NSd6aZbOxjhik=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WGQWvF/HpZtbP/5r+dh9VtFtEnxNlRAul3UAJ7phbrDqof3UF5Jip4l1miwijwlcn DoP5FZF2A0sf/A6+Bvvzq0zb8sxQzSwMSmUecPUn/3QHjnohG6xnipcbkc+3OnZBOG TR1HUEMIbcpIymQkS7WyjfQzeV70H54oGR8JpGsc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Nicholas Piggin , Michael Ellerman , Sasha Levin Subject: [PATCH 6.2 126/141] powerpc/64: Fix task_cpu in early boot when booting non-zero cpuid Date: Wed, 15 Mar 2023 13:13:49 +0100 Message-Id: <20230315115743.826453024@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230315115739.932786806@linuxfoundation.org> References: <20230315115739.932786806@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Nicholas Piggin [ Upstream commit 9fa24404f5044967753a6cd3e5e36f57686bec6e ] powerpc/64 can boot on a non-zero SMP processor id. Initially, the boot CPU is said to be "assumed to be 0" until early_init_devtree() discovers the id from the device tree. That is not a good description because the assumption can be wrong and that has to be handled, the better description is that 0 is used as a placeholder, and things are fixed after the real id is discovered. smp_processor_id() is set to the boot cpuid, but task_cpu(current) is not, which causes the smp_processor_id() == task_cpu(current) invariant to be broken until init_idle() in sched_init(). This is quite fragile and could lead to subtle bugs in future. One bug is that validate_sp_size uses task_cpu() to get the process stack, so any stack trace from the booting CPU between early_init_devtree() and sched_init() will have problems. Early on paca_ptrs[0] will be poisoned, so that can cause machine checks dereferencing that memory in real mode. Later, validating the current stack pointer against the idle task of a different secondary will probably cause no stack trace to be printed. Fix this by setting thread_info->cpu right after smp_processor_id() is set to the boot cpuid. Signed-off-by: Nicholas Piggin [mpe: Fix SMP=n build as reported by sfr] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221216115930.2667772-3-npiggin@gmail.com Signed-off-by: Sasha Levin --- arch/powerpc/kernel/setup_64.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index a0dee7354fe6b..a43865e0fb4bf 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -396,6 +396,11 @@ void __init early_setup(unsigned long dt_ptr) } fixup_boot_paca(paca_ptrs[boot_cpuid]); setup_paca(paca_ptrs[boot_cpuid]); /* install the paca into registers */ + // smp_processor_id() now reports boot_cpuid + +#ifdef CONFIG_SMP + task_thread_info(current)->cpu = boot_cpuid; // fix task_cpu(current) +#endif /* * Configure exception handlers. This include setting up trampolines -- 2.39.2