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=-7.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 F2C4EC5ACC6 for ; Tue, 16 Oct 2018 21:25:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9E24D205F4 for ; Tue, 16 Oct 2018 21:25:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="tLvcUXbr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9E24D205F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727123AbeJQFRj (ORCPT ); Wed, 17 Oct 2018 01:17:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:48992 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726697AbeJQFRj (ORCPT ); Wed, 17 Oct 2018 01:17:39 -0400 Received: from mail-wm1-f54.google.com (mail-wm1-f54.google.com [209.85.128.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4002421470 for ; Tue, 16 Oct 2018 21:25:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1539725121; bh=v/Fmzz9EAoi17bs+UG2hEWHX47GLZMTEqbmZso6OjPw=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=tLvcUXbr5ZQ+XmGKcbaQwLnPp4EXmVlWdi5b3nLmUzWJNiXSRx8eAWzmrRs/FiedX 60Zqx+66EO/QfHBX9V8+IncWTXeRbs+ADHGwJ+rRPpSYixpMMmwa0y67Bptq+pPOY4 JHJaDe38w/ngL1kMb0DrQmXPrvHrNYvQF4ddpmek= Received: by mail-wm1-f54.google.com with SMTP id 189-v6so23889868wmw.2 for ; Tue, 16 Oct 2018 14:25:21 -0700 (PDT) X-Gm-Message-State: ABuFfojfSqhPquxoPMea37rXbX+XbHXFynC//vlt9bGUJVWqdm99kOsU 7YwpNTWpkieZiFXVNRCQ4INrcJigI91dQfthd9tgqg== X-Google-Smtp-Source: ACcGV61zzMFyBPmRxVygb2WjI1RiBrdYngffa/8vkWyn6XD2NH1Wb9o+Qh1VUKvrixDMzPoc51f7JFYpgIMxhbC+Qlc= X-Received: by 2002:a1c:1fcd:: with SMTP id f196-v6mr18443248wmf.19.1539725119674; Tue, 16 Oct 2018 14:25:19 -0700 (PDT) MIME-Version: 1.0 References: <20181016202525.29437-1-bigeasy@linutronix.de> <20181016202525.29437-2-bigeasy@linutronix.de> In-Reply-To: <20181016202525.29437-2-bigeasy@linutronix.de> From: Andy Lutomirski Date: Tue, 16 Oct 2018 14:25:07 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/3] x86/mm/pat: Disable preemption around __flush_tlb_all() To: Sebastian Andrzej Siewior Cc: LKML , X86 ML , Dave Hansen , Andrew Lutomirski , Peter Zijlstra , Borislav Petkov Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 16, 2018 at 1:25 PM Sebastian Andrzej Siewior wrote: > > I've seen the WARN_ON_ONCE(__read_cr3() != build_cr3()) in > switch_mm_irqs_off() every once in a while during a snapshotted system > upgrade. > I also saw the warning early during which was introduced in commit > decab0888e6e ("x86/mm: Remove preempt_disable/enable() from > __native_flush_tlb()"). The callchain is > > get_page_from_freelist() -> post_alloc_hook() -> __kernel_map_pages() > > with CONFIG_DEBUG_PAGEALLOC enabled. > > Turns out, once I disable preemption around __flush_tlb_all() both > warnings do not appear. > > Disable preemption during CR3 reset / __flush_tlb_all(). > > Fixes: decab0888e6e ("x86/mm: Remove preempt_disable/enable() from __native_flush_tlb()") > Signed-off-by: Sebastian Andrzej Siewior > --- > arch/x86/mm/pageattr.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c > index 51a5a69ecac9f..fe6b21f0a6631 100644 > --- a/arch/x86/mm/pageattr.c > +++ b/arch/x86/mm/pageattr.c > @@ -2088,7 +2088,9 @@ void __kernel_map_pages(struct page *page, int numpages, int enable) > * We should perform an IPI and flush all tlbs, > * but that can deadlock->flush only current cpu: > */ > + preempt_disable(); > __flush_tlb_all(); > + preempt_enable(); > Depending on your CPU, __flush_tlb_all() is either __native_flush_tlb_global() or __native_flush_tlb(). Only __native_flush_tlb() could have any problem with preemption, but it has a WARN_ON_ONCE(preemptible()); in it. Can you try to figure out why that's not firing for you? I suspect that a better fix would be to put preempt_disable() into __native_flulsh_tlb(), but I'd still like to understand why the warning isn't working.