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=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 78F4AC433E7 for ; Mon, 12 Oct 2020 11:24:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4904E214D8 for ; Mon, 12 Oct 2020 11:24:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388197AbgJLLY6 (ORCPT ); Mon, 12 Oct 2020 07:24:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:52574 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388196AbgJLLY6 (ORCPT ); Mon, 12 Oct 2020 07:24:58 -0400 Received: from gaia (unknown [95.149.105.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DC4912076E; Mon, 12 Oct 2020 11:24:55 +0000 (UTC) Date: Mon, 12 Oct 2020 12:24:53 +0100 From: Catalin Marinas To: Ard Biesheuvel Cc: Linux ARM , ACPI Devel Maling List , Will Deacon , Jeremy Linton , Lorenzo Pieralisi , Nicolas Saenz Julienne , Rob Herring , Christoph Hellwig , Robin Murphy , Hanjun Guo , Sudeep Holla , Anshuman Khandual Subject: Re: [PATCH] arm64: mm: set ZONE_DMA size based on early IORT scan Message-ID: <20201012112453.GD9844@gaia> References: <20201010093153.30177-1-ardb@kernel.org> <20201012092821.GB9844@gaia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Mon, Oct 12, 2020 at 12:43:05PM +0200, Ard Biesheuvel wrote: > On Mon, 12 Oct 2020 at 11:30, Ard Biesheuvel wrote: > > On Mon, 12 Oct 2020 at 11:28, Catalin Marinas wrote: > > > On Sat, Oct 10, 2020 at 11:31:53AM +0200, Ard Biesheuvel wrote: > > > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > > > > index f0599ae73b8d..829fa63c3d72 100644 > > > > --- a/arch/arm64/mm/init.c > > > > +++ b/arch/arm64/mm/init.c > > > > @@ -191,6 +191,14 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) > > > > unsigned long max_zone_pfns[MAX_NR_ZONES] = {0}; > > > > > > > > #ifdef CONFIG_ZONE_DMA > > > > + if (IS_ENABLED(CONFIG_ACPI)) { > > > > + extern unsigned int acpi_iort_get_zone_dma_size(void); > > > > > > Nitpick: can we add this prototype to include/linux/acpi_iort.h? > > > > > > > + > > > > + zone_dma_bits = min(zone_dma_bits, > > > > + acpi_iort_get_zone_dma_size()); > > > > + arm64_dma_phys_limit = max_zone_phys(zone_dma_bits); > > > > + } > > > > + > > > > max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit); > > > > > > I think we should initialise zone_dma_bits slightly earlier via > > > arm64_memblock_init(). We'll eventually have reserve_crashkernel() > > > called before this and it will make use of arm64_dma_phys_limit for > > > "low" reservations: > > > > > > https://lore.kernel.org/linux-arm-kernel/20200907134745.25732-7-chenzhou10@huawei.com/ > > > > > > > We don't have access to the ACPI tables yet at that point. > > Also, could someone give an executive summary of why it matters where > the crashkernel is loaded? As far as I can tell, reserve_crashkernel() > only allocates memory for the kernel's executable image itself, which > can usually be loaded anywhere in memory. I could see how a > crashkernel might need some DMA'able memory if it needs to use the > hardware, but I don't think that is what is going on here. I thought the crashkernel needs some additional reserved RAM as well to be able to run. It should not touch the original kernel's memory as it usually needs to dump it. -- Catalin