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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 5861BC43387 for ; Tue, 8 Jan 2019 12:14:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D4D6206B7 for ; Tue, 8 Jan 2019 12:14:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728984AbfAHMOq (ORCPT ); Tue, 8 Jan 2019 07:14:46 -0500 Received: from foss.arm.com ([217.140.101.70]:50010 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728857AbfAHMOp (ORCPT ); Tue, 8 Jan 2019 07:14:45 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1D0481596; Tue, 8 Jan 2019 04:14:45 -0800 (PST) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B61413F70D; Tue, 8 Jan 2019 04:14:43 -0800 (PST) Date: Tue, 8 Jan 2019 12:14:41 +0000 From: Mark Rutland To: Miles Chen Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com Subject: Re: [PATCH] arm64: trap illegal translations in __virt_to_phys() Message-ID: <20190108121440.GC29102@lakrids.cambridge.arm.com> References: <1546860080-13027-1-git-send-email-miles.chen@mediatek.com> <20190107150019.GC46743@lakrids.cambridge.arm.com> <1546917883.6754.8.camel@mtkswgap22> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1546917883.6754.8.camel@mtkswgap22> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 08, 2019 at 11:24:43AM +0800, Miles Chen wrote: > On Mon, 2019-01-07 at 15:00 +0000, Mark Rutland wrote: > > On Mon, Jan 07, 2019 at 07:21:20PM +0800, Miles Chen wrote: > > > Current __virt_to_phys() only print warning messages for non-linear > > > addresses. It's hard to catch all warnings by those messages. > > > > Why? Are you seeing a large number of warnings somewhere? > > Official kernel works fine. I saw some cases in our internal branch and > we're fixing them. > > > > > > So add a VIRTUAL_BUG_ON() to trap all non-linear and non-symbol > > > addresses (e.g., stack addresses) > > > > > > Tested by pass stack addresses and symbol addresses to __pa(). Result: > > > stack addresses: kernel BUG() > > > > Either: > > > > * Stacks are vmap'd, and __is_lm_address(stack_addr) is false. We'll > > produce a WARNING() today (and return a junk physical address). > > > > * Stacks are linear mapped, and cannot be distinguished from other > > linear mapped addresses. The physical address will be valid. > > > > ... so I don't understand why you need to change this. > > For the first case: for vmap'd stack, __pa() returns a junk > physical address and it might be easier to debug this incorrect address > translation by a BUG() call instead of monitoring the warning log. I think that's an argument for upgrading the existing WARN() to a BUG(), rather than adding a separate VIRTUAL_BUG_ON(). However, there are cases where the junk physical address is not used to perform an access, and the WARN() is more helpful. You can set panic_on_warn to get an immediate panic() when the WARN() fires. Is there some reason that approach doesn't work for you? Thanks, Mark.