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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 0CAB6C433DF for ; Mon, 12 Oct 2020 16:59:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C2BEC20878 for ; Mon, 12 Oct 2020 16:59:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390705AbgJLQ7i (ORCPT ); Mon, 12 Oct 2020 12:59:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:41056 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390541AbgJLQ7i (ORCPT ); Mon, 12 Oct 2020 12:59:38 -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 E091E2080A; Mon, 12 Oct 2020 16:59:35 +0000 (UTC) Date: Mon, 12 Oct 2020 17:59:33 +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: <20201012165933.GD6493@gaia> References: <20201010093153.30177-1-ardb@kernel.org> <20201012092821.GB9844@gaia> <20201012112453.GD9844@gaia> <20201012154954.GB6493@gaia> <20201012162238.GC6493@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 06:35:37PM +0200, Ard Biesheuvel wrote: > On Mon, 12 Oct 2020 at 18:22, Catalin Marinas wrote: > > On Mon, Oct 12, 2020 at 05:55:45PM +0200, Ard Biesheuvel wrote: > > > On Mon, 12 Oct 2020 at 17:50, Catalin Marinas wrote: > > > > > > On Mon, Oct 12, 2020 at 12:43:05PM +0200, Ard Biesheuvel wrote: > > > > > > > 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. > > [...] > > > > However, the crashkernel=... range is meant for sufficiently large > > > > reservation to be able to run the kdump kernel, not just load the image. > > > > > > Sure. But I was referring to the requirement that it is loaded low in > > > memory. Unless I am misunderstanding something, all we need for the > > > crashkernel to be able to operate is some ZONE_DMA memory in case it > > > is needed by the hardware, and beyond that, it could happily live > > > anywhere in memory. > > > > Yes, the crash kernel doesn't need to be loaded in the low memory. But > > some low memory needs to end up in its perceived System RAM. That's what > > Chen is trying to do with this series: > > > > https://lore.kernel.org/linux-arm-kernel/20200907134745.25732-1-chenzhou10@huawei.com/ > > > > It reserves the normal crashkernel memory at some high address range > > with a small block (currently proposed as 256MB similar to x86) in the > > "low" range. > > > > This "low" range for arm64 currently means below 1GB but it's only RPi4 > > that needs it this low, all other platforms are fine with the full low > > 32-bit range. > > > > If it's not doable in a nice way, we'll just leave with this permanent > > 1GB ZONE_DMA and hope we won't get platforms requiring an even smaller > > one. There's also the option of ignoring kdump on RPi4, make ZONE_DMA > > depend on !CRASH_DUMP and the "low" reservations can use the full 32-bit > > range since the kdump kernel won't need <30-bit addresses. > > Are you aware of any reason why we cannot defer the call to > reserve_crashkernel() to the start of bootmem_init()? That way, we > have access to the unflattened DT as well as the IORT, and so we can > tweak the zone limits based on the h/w description, but before > allocating the crashkernel. Not really, as long as memblock_reserve/alloc() still works. -- Catalin 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=-5.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 94705C433DF for ; Mon, 12 Oct 2020 17:01:11 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 400752080A for ; Mon, 12 Oct 2020 17:01:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="WiyhO2p0" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 400752080A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=b6AitFR74X7AeTn9mxc54imQLMO2ULSlojay3R7F1vI=; b=WiyhO2p0qpcewEH/dbJtkCghG 1s9mJMjQ6MhzhftfYUymuTqVyeHrUfI6kYSdmHqQijvWjGahqP9MyCVttLqbkGr0v75gyxC5/Q41Q hXAK6pY6eXuZLdGuxPJ/a772dITTOYcw08/jPqlFNS7iAieINI1RlK9egCPUTfBW+QbaNyoWQLibt hXOMVJtNK92KIr7PONY1cn4b+9vg0wCjZJnn+gcgFBGjJdl2JLQzFs5pObosshW4yMSruQvUTiv2v lRQYpb7zoUKONRhLjQ5CgrLqd+Le0p3QSO0YXUmgGkojK9JpekZlaNV1i/7JAw+MhChfcsSWuy6ro 6D1W+aWZw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kS1Al-00022Y-M6; Mon, 12 Oct 2020 16:59:43 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kS1Ah-00021t-Do for linux-arm-kernel@lists.infradead.org; Mon, 12 Oct 2020 16:59:41 +0000 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 E091E2080A; Mon, 12 Oct 2020 16:59:35 +0000 (UTC) Date: Mon, 12 Oct 2020 17:59:33 +0100 From: Catalin Marinas To: Ard Biesheuvel Subject: Re: [PATCH] arm64: mm: set ZONE_DMA size based on early IORT scan Message-ID: <20201012165933.GD6493@gaia> References: <20201010093153.30177-1-ardb@kernel.org> <20201012092821.GB9844@gaia> <20201012112453.GD9844@gaia> <20201012154954.GB6493@gaia> <20201012162238.GC6493@gaia> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201012_125939_594344_F8694F9B X-CRM114-Status: GOOD ( 31.96 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Lorenzo Pieralisi , Anshuman Khandual , Robin Murphy , Sudeep Holla , Jeremy Linton , ACPI Devel Maling List , Rob Herring , Linux ARM , Hanjun Guo , Will Deacon , Christoph Hellwig , Nicolas Saenz Julienne Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Oct 12, 2020 at 06:35:37PM +0200, Ard Biesheuvel wrote: > On Mon, 12 Oct 2020 at 18:22, Catalin Marinas wrote: > > On Mon, Oct 12, 2020 at 05:55:45PM +0200, Ard Biesheuvel wrote: > > > On Mon, 12 Oct 2020 at 17:50, Catalin Marinas wrote: > > > > > > On Mon, Oct 12, 2020 at 12:43:05PM +0200, Ard Biesheuvel wrote: > > > > > > > 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. > > [...] > > > > However, the crashkernel=... range is meant for sufficiently large > > > > reservation to be able to run the kdump kernel, not just load the image. > > > > > > Sure. But I was referring to the requirement that it is loaded low in > > > memory. Unless I am misunderstanding something, all we need for the > > > crashkernel to be able to operate is some ZONE_DMA memory in case it > > > is needed by the hardware, and beyond that, it could happily live > > > anywhere in memory. > > > > Yes, the crash kernel doesn't need to be loaded in the low memory. But > > some low memory needs to end up in its perceived System RAM. That's what > > Chen is trying to do with this series: > > > > https://lore.kernel.org/linux-arm-kernel/20200907134745.25732-1-chenzhou10@huawei.com/ > > > > It reserves the normal crashkernel memory at some high address range > > with a small block (currently proposed as 256MB similar to x86) in the > > "low" range. > > > > This "low" range for arm64 currently means below 1GB but it's only RPi4 > > that needs it this low, all other platforms are fine with the full low > > 32-bit range. > > > > If it's not doable in a nice way, we'll just leave with this permanent > > 1GB ZONE_DMA and hope we won't get platforms requiring an even smaller > > one. There's also the option of ignoring kdump on RPi4, make ZONE_DMA > > depend on !CRASH_DUMP and the "low" reservations can use the full 32-bit > > range since the kdump kernel won't need <30-bit addresses. > > Are you aware of any reason why we cannot defer the call to > reserve_crashkernel() to the start of bootmem_init()? That way, we > have access to the unflattened DT as well as the IORT, and so we can > tweak the zone limits based on the h/w description, but before > allocating the crashkernel. Not really, as long as memblock_reserve/alloc() still works. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel