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=-2.3 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 3C805ECDFAA for ; Wed, 18 Jul 2018 06:14:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E2FEA2075E for ; Wed, 18 Jul 2018 06:14:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E2FEA2075E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1726988AbeGRGuR (ORCPT ); Wed, 18 Jul 2018 02:50:17 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:34048 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726258AbeGRGuR (ORCPT ); Wed, 18 Jul 2018 02:50:17 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E39E54106D21; Wed, 18 Jul 2018 06:14:03 +0000 (UTC) Received: from dhcp-128-65.nay.redhat.com (ovpn-12-41.pek2.redhat.com [10.72.12.41]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4B81E2026D74; Wed, 18 Jul 2018 06:13:54 +0000 (UTC) Date: Wed, 18 Jul 2018 14:13:50 +0800 From: Dave Young To: AKASHI Takahiro , James Morse , catalin.marinas@arm.com, will.deacon@arm.com, dhowells@redhat.com, vgoyal@redhat.com, herbert@gondor.apana.org.au, davem@davemloft.net, bhe@redhat.com, arnd@arndb.de, ard.biesheuvel@linaro.org, bhsharma@redhat.com, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, "Eric W. Biederman" Subject: Re: [PATCH v11 03/15] powerpc, kexec_file: factor out memblock-based arch_kexec_walk_mem() Message-ID: <20180718061350.GA5086@dhcp-128-65.nay.redhat.com> References: <20180711074203.3019-1-takahiro.akashi@linaro.org> <20180711074203.3019-4-takahiro.akashi@linaro.org> <20180714015223.GA2745@dhcp-128-65.nay.redhat.com> <2a4ec965-5258-5835-3022-8f403a2f6bdd@arm.com> <20180716122412.GA7160@dhcp-128-65.nay.redhat.com> <20180717053104.GB11258@linaro.org> <20180717074923.GA8591@dhcp-128-65.nay.redhat.com> <20180718053818.GF11258@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180718053818.GF11258@linaro.org> User-Agent: Mutt/1.9.5 (2018-04-13) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 18 Jul 2018 06:14:04 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 18 Jul 2018 06:14:04 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'dyoung@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi AKASHI, On 07/18/18 at 02:38pm, AKASHI Takahiro wrote: > Dave, > > On Tue, Jul 17, 2018 at 03:49:23PM +0800, Dave Young wrote: > > Hi AKASHI, > > On 07/17/18 at 02:31pm, AKASHI Takahiro wrote: > > > Hi Dave, > > > > > > On Mon, Jul 16, 2018 at 08:24:12PM +0800, Dave Young wrote: > > > > On 07/16/18 at 12:04pm, James Morse wrote: > > > > > Hi Dave, > > > > > > > > > > On 14/07/18 02:52, Dave Young wrote: > > > > > > On 07/11/18 at 04:41pm, AKASHI Takahiro wrote: > > > > > >> Memblock list is another source for usable system memory layout. > > > > > >> So powerpc's arch_kexec_walk_mem() is moved to kexec_file.c so that > > > > > >> other memblock-based architectures, particularly arm64, can also utilise > > > > > >> it. A moved function is now renamed to kexec_walk_memblock() and merged > > > > > >> into the existing arch_kexec_walk_mem() for general use, either resource > > > > > >> list or memblock list. > > > > > >> > > > > > >> A consequent function will not work for kdump with memblock list, but > > > > > >> this will be fixed in the next patch. > > > > > > > > > > >> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > > > > > > > > > > >> @@ -513,6 +563,10 @@ static int locate_mem_hole_callback(struct resource *res, void *arg) > > > > > >> int __weak arch_kexec_walk_mem(struct kexec_buf *kbuf, > > > > > >> int (*func)(struct resource *, void *)) > > > > > >> { > > > > > >> + if (IS_ENABLED(CONFIG_HAVE_MEMBLOCK) && > > > > > >> + !IS_ENABLED(CONFIG_ARCH_DISCARD_MEMBLOCK)) > > > > > >> + return kexec_walk_memblock(kbuf, func); > > > > > > > > > > > > AKASHI, I'm not sure if this works on all arches, for example I chekced > > > > > > the .config on my Nokia N900 kernel tree, there is HAVE_MEMBLOCK=y and > > > > > > no CONFIG_ARCH_DISCARD_MEMBLOCK, in 32bit arm code no arch_kexec_walk_mem() > > > > > By doesn't work you mean it's a change in behaviour? > > > > > I think this is fine because 32bit arm doesn't support KEXEC_FILE, (this file is > > > > > kexec_file specific right?). > > > > > > > > Ah, replied on a train, I forgot this is only for kexec_file, sorry > > > > about that. Please ignore the comment. > > > > > > > > But since we have a weak function arch_kexec_walk_mem, adding another > > > > condition branch within this weak function looks not good. > > > > Something like below would be better: > > > > > > I see your concern here, but > > > > > > > > > > int kexec_locate_mem_hole(struct kexec_buf *kbuf) > > > > { > > > > int ret; > > > > > > > > + if use memblock > > > > + ret = kexec_walk_memblock() > > > > + else > > > > ret = arch_kexec_walk_mem(kbuf, locate_mem_hole_callback); > > > > > > > > return ret == 1 ? 0 : -EADDRNOTAVAIL; > > > > } > > > > > > what if yet another architecture comes to kexec_file and wanna > > > take a third approach? How can it override those functions? > > > Depending on kernel configuration, it might re-define either > > > kexec_walk_memblock() or arch_kexec_walk_mem(). It sounds weird to me. > > > > I also feel this weird, but it is slightly better because currently no > > user need another overriding requirement, and I feel it is not expected to have in > > the future for the memblock use. > > > > Rethinking about this issue, we can just remove the weak function and > > just use general function. > > Do you really want to remove "weak" attribute? > > > Currently with your patch applied only s390 use arch_kexec_walk_mem like > > below: > > /* > > * The kernel is loaded to a fixed location. Turn off kexec_locate_mem_hole > > * and provide kbuf->mem by hand. > > */ > > int arch_kexec_walk_mem(struct kexec_buf *kbuf, > > int (*func)(struct resource *, void *)) > > { > > return 1; > > } > > > > AFAIK, all other users initialize kbuf->mem as NULL, so we can check > > As a matter of fact, nobody initializes kbuf->mem before calling > kexec_add_buffer (in turn, kexec_locate_mem_hole()). Not sure we understand each other.. Let's take an example in arch/x86/kernel/kexec-bzimage64.c: bzImage64_load() : struct kexec_buf kbuf = { .image = image, .buf_max = ULONG_MAX, .top_down = true }; Except the three fields above other members will be initialized as zero when compiling including the kbuf->mem > > > kbuf->mem in int kexec_locate_mem_hole: > > > > if (kbuf->mem) > > return 0; > > > > if use memblock > > kexec_walk_memblock > > else > > kexec_walk_mem kexec_walk_resource will be better than kexec_walk_mem > > I think that your solution will work for existing architectures > with appropriate patches, but to take your approach, as I said above, > we will have to modify every call site on all kexec_file-capable architectures. > > If this is what you expect, I will work on it, but I don't think > that it would be a better idea. > > Thanks, > -Takahiro AKASHI > > > > > > > Thanks, > > > -Takahiro AKASHI > > > > > > > > > > > > > > > > > It only affects architectures with MEMBLOCK and KEXEC_FILE: powerpc, s390 and > > > > > soon arm64. s390 keeps its behaviour because it provides arch_kexec_walk_mem(), > > > > > and powerpc's is copied in here as its generic 'memblock describes my memory' > > > > > stuff. The implementation would be the same on arm64, so we're doing this to > > > > > avoid duplicating otherwise generic arch code. I think 32bit arm should be able > > > > > to use this too if it gets KEXEC_FILE support. (32bit arms' KEXEC already > > > > > depends on MEMBLOCK). > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > James > > > > > > > > Thanks > > > > Dave > > > > Thanks > > Dave Thanks dave