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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BCF21C433EF for ; Mon, 27 Jun 2022 10:35:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233779AbiF0Kf5 (ORCPT ); Mon, 27 Jun 2022 06:35:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40422 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231252AbiF0Kfy (ORCPT ); Mon, 27 Jun 2022 06:35:54 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 4BE9063CE for ; Mon, 27 Jun 2022 03:35:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1656326151; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=xKvZnCkoXt+4PjaORqXBx6ym+v+SmPmR3DG/cTeVOIc=; b=TyCWNKVAb/jGQKWqnpdEbxcUdezIaNlFe8FKKlNxzFatZryfVVNiLb25mfAp0qtdwTo21X nxNd59oG2pOlJkjWHU0Gnrbq3Cq6XwwL6WwtytXT9mHk0a/qNqkthXxywzSFit+nZk1PKf P02Cg8AnRl93tPOi3XiBAfsYlBABIeA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-326-MRuSKrRuP0GnZrfy_gPN4Q-1; Mon, 27 Jun 2022 06:35:48 -0400 X-MC-Unique: MRuSKrRuP0GnZrfy_gPN4Q-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CE66F101A586; Mon, 27 Jun 2022 10:35:47 +0000 (UTC) Received: from localhost (ovpn-13-65.pek2.redhat.com [10.72.13.65]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1CA9E492CA3; Mon, 27 Jun 2022 10:35:46 +0000 (UTC) Date: Mon, 27 Jun 2022 18:35:43 +0800 From: Baoquan He To: Tao Liu Cc: vgoyal@redhat.com, dyoung@redhat.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org Subject: Re: [PATCH v2] kdump: round up the total memory size to 128M for crashkernel reservation Message-ID: References: <20220627074440.187222-1-ltao@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220627074440.187222-1-ltao@redhat.com> X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/27/22 at 03:44pm, Tao Liu wrote: > The total memory size we get in kernel is usually slightly less than > the actual memory size because BIOS/firmware will reserve some memory > region. So it won't export all memory as usable. > > E.g, on my x86_64 kvm guest with 1G memory, the total_mem value shows: > UEFI boot with ovmf: 0x3faef000 > Legacy boot kvm guest: 0x3ff7ec00 > > When specifying crashkernel=1G-2G:128M, if we have a 1G memory machine, > we get total size 1023M from firmware. Then it will not fall into > 1G-2G, thus no memory reserved. User will never know this, it is hard > to let user know the exact total value in kernel. > > One way is to use dmi/smbios to get physical memory size, but it's not > reliable as well. According to Prarit hardware vendors sometimes screw > this up. Thus round up total size to 128M to work around this problem. > > This patch is a resend of [1] and rebased onto v5.19-rc2, and the > original credit goes to Dave Young . This should be put into cover letter, or put together with change log. Other than this, LGTM, Acked-by: Baoquan He > > [1]: http://lists.infradead.org/pipermail/kexec/2018-April/020568.html > > Signed-off-by: Tao Liu > --- > v1 -> v2: > Modified commit log based on Baoquan's advice. > --- > kernel/crash_core.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > index 71122e01623c..b58b27cbdb61 100644 > --- a/kernel/crash_core.c > +++ b/kernel/crash_core.c > @@ -9,6 +9,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -43,6 +44,15 @@ static int __init parse_crashkernel_mem(char *cmdline, > unsigned long long *crash_base) > { > char *cur = cmdline, *tmp; > + unsigned long long total_mem = system_ram; > + > + /* > + * Firmware sometimes reserves some memory regions for its own use, > + * so the system memory size is less than the actual physical memory > + * size. Work around this by rounding up the total size to 128M, > + * which is enough for most test cases. > + */ > + total_mem = roundup(total_mem, SZ_128M); > > /* for each entry of the comma-separated list */ > do { > @@ -87,13 +97,13 @@ static int __init parse_crashkernel_mem(char *cmdline, > return -EINVAL; > } > cur = tmp; > - if (size >= system_ram) { > + if (size >= total_mem) { > pr_warn("crashkernel: invalid size\n"); > return -EINVAL; > } > > /* match ? */ > - if (system_ram >= start && system_ram < end) { > + if (total_mem >= start && total_mem < end) { > *crash_size = size; > break; > } > -- > 2.33.1 >