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=-5.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,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 5F21EC433E7 for ; Mon, 19 Oct 2020 02:45:30 +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 EA61822269 for ; Mon, 19 Oct 2020 02:45:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="uEZxXBj3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA61822269 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.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:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=bMe//VK9L4aO3a8dWXd2EREWaTs8ZQ/z7bgZXWY31nU=; b=uEZxXBj3TeK9k0vZbmBJbCUpl kdsCto8iDJmzd8SAnku1K7G8ZM0qR021uHWM7BuIYW61utqwlP7eYeBse48dzX0onAnrxwqTZV5cB Tn1kpeVFIdaN1VGZ4t7qTx5yWB48JPcznScFBQ04BOC+NUEqbh0rxblOakXm0aCirNP0x4Cn4lSzB vaghO0lku2T7C2W1jRNes1yHV4OqnaMs5ihpml9Z5V4XAVJcjY3T38SXqc6vaGnEo0CjBiag3mJX8 HqVLqfPRbW+RF8pJpLFEvn6NG8OtEppdKdLw+owTPycPPVb4g2aZA5zCBl3ij/HMN3i6OAB7rZgN0 8Gy3fm7oA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kUL93-0000lM-5r; Mon, 19 Oct 2020 02:43:33 +0000 Received: from szxga06-in.huawei.com ([45.249.212.32] helo=huawei.com) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kUL8y-0000k8-CM; Mon, 19 Oct 2020 02:43:29 +0000 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 0E4BB91A978CEDFB0FE2; Mon, 19 Oct 2020 10:43:15 +0800 (CST) Received: from [10.174.176.61] (10.174.176.61) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.487.0; Mon, 19 Oct 2020 10:43:07 +0800 Subject: Re: [PATCH v12 0/9] support reserving crashkernel above 4G on arm64 kdump To: Bhupesh Sharma , Catalin Marinas References: <20200907134745.25732-1-chenzhou10@huawei.com> <20201005170937.GA14576@gaia> <20201006180012.GB31946@C02TF0J2HF1T.local> From: chenzhou Message-ID: Date: Mon, 19 Oct 2020 10:43:05 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.174.176.61] X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201018_224328_678939_38B790E1 X-CRM114-Status: GOOD ( 26.10 ) 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: Simon Horman , John Donnelly , guohanjun@huawei.com, xiexiuqi@huawei.com, Arnd Bergmann , Baoquan He , Jonathan Corbet , Will Deacon , Linux Doc Mailing List , kexec mailing list , Linux Kernel Mailing List , Rob Herring , wangkefeng.wang@huawei.com, Ingo Molnar , James Morse , linux-arm-kernel , huawei.libin@huawei.com, Prabhakar Kushwaha , Thomas Gleixner , RuiRui Yang , nsaenzjulienne@suse.de 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 Hi Bhupesh, On 2020/10/7 15:07, Bhupesh Sharma wrote: > Hi Catalin, > > On Tue, Oct 6, 2020 at 11:30 PM Catalin Marinas wrote: >> On Mon, Oct 05, 2020 at 11:12:10PM +0530, Bhupesh Sharma wrote: >>> I think my earlier email with the test results on this series bounced >>> off the mailing list server (for some weird reason), but I still see >>> several issues with this patchset. I will add specific issues in the >>> review comments for each patch again, but overall, with a crashkernel >>> size of say 786M, I see the following issue: >>> >>> # cat /proc/cmdline >>> BOOT_IMAGE=(hd7,gpt2)/vmlinuz-5.9.0-rc7+ root=<..snip..> rd.lvm.lv=<..snip..> crashkernel=786M >>> >>> I see two regions of size 786M and 256M reserved in low and high >>> regions respectively, So we reserve a total of 1042M of memory, which >>> is an incorrect behaviour: >>> >>> # dmesg | grep -i crash >>> [ 0.000000] Reserving 256MB of low memory at 2816MB for crashkernel (System low RAM: 768MB) >>> [ 0.000000] Reserving 786MB of memory at 654158MB for crashkernel (System RAM: 130816MB) >>> [ 0.000000] Kernel command line: BOOT_IMAGE=(hd2,gpt2)/vmlinuz-5.9.0-rc7+ root=/dev/mapper/rhel_ampere--hr330a--03-root ro rd.lvm.lv=rhel_ampere-hr330a-03/root rd.lvm.lv=rhel_ampere-hr330a-03/swap crashkernel=786M cma=1024M >>> >>> # cat /proc/iomem | grep -i crash >>> b0000000-bfffffff : Crash kernel (low) >>> bfcbe00000-bffcffffff : Crash kernel >> As Chen said, that's the intended behaviour and how x86 works. The >> requested 768M goes in the high range if there's not enough low memory >> and an additional buffer for swiotlb is allocated, hence the low 256M. > I understand, but why 256M (as low) for arm64? x86_64 setups usually > have more system memory available as compared to several commercially > available arm64 setups. So is the intent, just to keep the behavior > similar between arm64 and x86_64? > > Should we have a CONFIG option / bootarg to help one select the max > 'low_size'? Currently the ' low_size' value is calculated as: > > /* > * two parts from kernel/dma/swiotlb.c: > * -swiotlb size: user-specified with swiotlb= or default. > * > * -swiotlb overflow buffer: now hardcoded to 32k. We round it > * to 8M for other buffers that may need to stay low too. Also > * make sure we allocate enough extra low memory so that we > * don't run out of DMA buffers for 32-bit devices. > */ > low_size = max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20); > > Since many arm64 boards ship with swiotlb=0 (turned off) via kernel > bootargs, the low_size, still ends up being 256M in such cases, > whereas this 256M can be used for some other purposes - so should we > be limiting this to 64M and failing the crash kernel allocation > request (gracefully) otherwise? > >> We could (as an additional patch), subtract the 256M from the high >> allocation so that you'd get a low 256M and a high 512M, not sure it's >> worth it. Note that with a "crashkernel=768M,high" option, you still get >> the additional low 256M, otherwise the crashkernel won't be able to >> boot as there's no memory in ZONE_DMA. In the explicit ",high" request >> case, I'm not sure subtracted the 256M is more intuitive. >> In 5.11, we also hope to fix the ZONE_DMA layout for non-RPi4 platforms >> to cover the entire 32-bit address space (i.e. identical to the current >> ZONE_DMA32). >> >>> IMO, we should test this feature more before including this in 5.11 >> Definitely. That's one of the reasons we haven't queued it yet. So any >> help with testing here is appreciated. > Sure, I am running more checks on this series. I will be soon back > with more updates. Sorry to bother you. I am looking forward to your review comments. Thanks, Chen Zhou > > Regards, > Bhupesh > > . > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel