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=-16.0 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 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 72A81C63697 for ; Wed, 18 Nov 2020 00:45:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1059F24198 for ; Wed, 18 Nov 2020 00:45:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="LRWj38G+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727681AbgKRApb (ORCPT ); Tue, 17 Nov 2020 19:45:31 -0500 Received: from mail.kernel.org ([198.145.29.99]:35792 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725767AbgKRApa (ORCPT ); Tue, 17 Nov 2020 19:45:30 -0500 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8E94324181; Wed, 18 Nov 2020 00:45:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605660329; bh=WQtSwGawLcx5cNeiXXUE0xzq9xL1NO7N+lP3KuaOZck=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LRWj38G++Gq39Byx9+ahpj6HYYOiiqlHK/cjkQcThMQuKvT3gDUOLAS3DFMvyFilt c7pg4ZmmfqQ+YNHbYd1ibSNCS0Vkc8aVj1aYZGfi3fbSPvRdQc0M2HLs7igyBr0K7N +KezrqksYdcU0xVCnc66s86vfiHoWW5I2HJMMlsI= Date: Tue, 17 Nov 2020 19:45:28 -0500 From: Sasha Levin To: Kamal Mostafa Cc: Michael Ellerman , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Nicholas Piggin , "Peter Zijlstra (Intel)" Subject: Re: Same problem for 4.14.y and a concern: Re: [PATCH 4.19 056/191] powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM Message-ID: <20201118004528.GA629656@sasha-vm> References: <20201103203232.656475008@linuxfoundation.org> <20201103203239.940977599@linuxfoundation.org> <87361qug5a.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 17, 2020 at 10:51:16AM -0800, Kamal Mostafa wrote: >On Tue, Nov 3, 2020 at 4:22 PM Michael Ellerman wrote: > >> Greg Kroah-Hartman writes: >> > From: Nicholas Piggin >> > >> > [ Upstream commit 66acd46080bd9e5ad2be4b0eb1d498d5145d058e ] >> > >> > powerpc uses IPIs in some situations to switch a kernel thread away >> > from a lazy tlb mm, which is subject to the TLB flushing race >> > described in the changelog introducing ARCH_WANT_IRQS_OFF_ACTIVATE_MM. >> > >> > Signed-off-by: Nicholas Piggin >> > Signed-off-by: Michael Ellerman >> > Link: >> https://lore.kernel.org/r/20200914045219.3736466-3-npiggin@gmail.com >> > Signed-off-by: Sasha Levin >> > --- >> > arch/powerpc/Kconfig | 1 + >> > arch/powerpc/include/asm/mmu_context.h | 2 +- >> > 2 files changed, 2 insertions(+), 1 deletion(-) >> > >> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig >> > index f38d153d25861..0bc53f0e37c0f 100644 >> > --- a/arch/powerpc/Kconfig >> > +++ b/arch/powerpc/Kconfig >> > @@ -152,6 +152,7 @@ config PPC >> > select ARCH_USE_BUILTIN_BSWAP >> > select ARCH_USE_CMPXCHG_LOCKREF if PPC64 >> > select ARCH_WANT_IPC_PARSE_VERSION >> > + select ARCH_WANT_IRQS_OFF_ACTIVATE_MM >> >> This depends on upstream commit: >> >> d53c3dfb23c4 ("mm: fix exec activate_mm vs TLB shootdown and lazy tlb >> switching race") >> >> >> Which I don't see in 4.19 stable, or in the email thread here. >> >> So this shouldn't be backported to 4.19 unless that commit is also >> backported. >> >> cheers >> > >Hi- > >This glitch has made its way into 4.14.y ... > [4.14.y] c2bca8712a19 powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM >But 4.14.y does not carry the prereq that introduces that config. I'll queue up the 4.19 backport for 4.14 too, thanks! -- Thanks, Sasha