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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 4D9D0C43381 for ; Thu, 28 Feb 2019 15:14:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1D1E9218C3 for ; Thu, 28 Feb 2019 15:14:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388718AbfB1POs (ORCPT ); Thu, 28 Feb 2019 10:14:48 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:49738 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388706AbfB1POm (ORCPT ); Thu, 28 Feb 2019 10:14:42 -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 5B0B7A78; Thu, 28 Feb 2019 07:14:42 -0800 (PST) Received: from fuggles.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 9255E3F720; Thu, 28 Feb 2019 07:14:41 -0800 (PST) Date: Thu, 28 Feb 2019 15:14:36 +0000 From: Will Deacon To: Sasha Levin Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH AUTOSEL 4.20 60/81] arm64: ptdump: Don't iterate kernel page tables using PTRS_PER_PXX Message-ID: <20190228151436.GA8571@fuggles.cambridge.arm.com> References: <20190228150813.10256-1-sashal@kernel.org> <20190228150813.10256-60-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190228150813.10256-60-sashal@kernel.org> User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 28, 2019 at 10:07:52AM -0500, Sasha Levin wrote: > From: Will Deacon > > [ Upstream commit d23c808c6fc6132e812690648e14c0d6b0cbe273 ] > > When 52-bit virtual addressing is enabled for userspace > (CONFIG_ARM64_USER_VA_BITS_52=y), the kernel continues to utilise 48-bit > virtual addressing in TTBR1. Consequently, PTRS_PER_PGD reflects the > larger page table size for userspace and the pgd pointer for kernel page > tables is offset before being written to TTBR1. > > This means that we can't use PTRS_PER_PGD to iterate over kernel page > tables unless we apply the same offset, which is fiddly to get right and > leads to some non-idiomatic walking code. Instead, just follow the usual > pattern when walking page tables by using a while loop driven by > pXd_offset() and pXd_addr_end(). > > Reported-by: Qian Cai > Tested-by: Qian Cai > Acked-by: Steve Capper > Tested-by: Steve Capper > Signed-off-by: Will Deacon > Signed-off-by: Sasha Levin > --- > arch/arm64/mm/dump.c | 59 ++++++++++++++++++++++---------------------- > 1 file changed, 29 insertions(+), 30 deletions(-) 4.20 doesn't support 52-bit VAs, so this isn't needed there afaict (and is why I didn't tag the commit for stable in the first place). Will