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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,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 A2CCBC47082 for ; Tue, 8 Jun 2021 21:14:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 853C16044F for ; Tue, 8 Jun 2021 21:14:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233934AbhFHVQG (ORCPT ); Tue, 8 Jun 2021 17:16:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:36708 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229526AbhFHVQF (ORCPT ); Tue, 8 Jun 2021 17:16:05 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 52E3660FD8; Tue, 8 Jun 2021 21:14:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1623186852; bh=G2smJxvAvuJyR2PVlfkCgvduPlzSv6hHhHX7NFNY20I=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=FSXWgxmd8Uuly+8F/DNMxKu28peM0aEDJWzKxZhCGVBW3OFtmBlFiFDRnIaxVwEjp U+bMQ8ZGcX8xc9CsXU0xGdx9cw1evm79PHu5nuqSh5775dEpcL/aIdLs0/8ZpVRs0n pieXRb46jjM8WiXkFPegtAY9/fQA7BshRhnEuDpc= Date: Tue, 8 Jun 2021 14:14:10 -0700 From: Andrew Morton To: Baoquan He Cc: Pingfan Liu , Bhupesh Sharma , Kazuhito Hagio , Dave Young , Boris Petkov , Ingo Molnar , Thomas Gleixner , James Morse , Mark Rutland , Will Deacon , Catalin Marinas , Michael Ellerman , Paul Mackerras , Benjamin Herrenschmidt , Dave Anderson , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] crash_core, vmcoreinfo: Append 'SECTION_SIZE_BITS' to vmcoreinfo Message-Id: <20210608141410.0026a925ba3a609b0dd4e560@linux-foundation.org> In-Reply-To: <20210608142432.GA587883@MiWiFi-R3L-srv> References: <20210608103359.84907-1-kernelfans@gmail.com> <20210608142432.GA587883@MiWiFi-R3L-srv> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 8 Jun 2021 22:24:32 +0800 Baoquan He wrote: > On 06/08/21 at 06:33am, Pingfan Liu wrote: > > As mentioned in kernel commit 1d50e5d0c505 ("crash_core, vmcoreinfo: > > Append 'MAX_PHYSMEM_BITS' to vmcoreinfo"), SECTION_SIZE_BITS in the > > formula: > > #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS) > > > > Besides SECTIONS_SHIFT, SECTION_SIZE_BITS is also used to calculate > > PAGES_PER_SECTION in makedumpfile just like kernel. > > > > Unfortunately, this arch-dependent macro SECTION_SIZE_BITS changes, e.g. > > recently in kernel commit f0b13ee23241 ("arm64/sparsemem: reduce > > SECTION_SIZE_BITS"). But user space wants a stable interface to get this > > info. Such info is impossible to be deduced from a crashdump vmcore. > > Hence append SECTION_SIZE_BITS to vmcoreinfo. > > ... > > Add the discussion of the original thread in kexec ML for reference: > http://lists.infradead.org/pipermail/kexec/2021-June/022676.html I added a Link: for this. > This looks good to me. > > Acked-by: Baoquan He I'm thinking we should backport this at least to Fixes:f0b13ee23241. But perhaps it's simpler to just backport it as far as possible, so I added a bare cc:stable with no Fixes:. Thoughts?