From patchwork Fri Feb 3 07:57:23 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baoquan He X-Patchwork-Id: 13127114 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7933AC61DA4 for ; Fri, 3 Feb 2023 07:58:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:Cc :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=giewNQjLz5ZF4bjMcHWqVqM8i+F+mBmhOrAepa7XIa4=; b=CpYa+qGkzK/oP+ PR4klFWEih5OaJBooz+UD6BNxGXO8OInBAW7ig9L39B5M4pE0UJUhOLrDrUfdDPDjBjUu27jeIskT 0H/ljNQ24gLj0smSiy7AlbA/q9SqAzCIZsIQcEvQDclOQo5/Sd/OpprxucuMchdymrv2SaupsMahh z9qFDYAYGvMUXs8wYEzOSvo9LEXre77qUarYjk2RVwnfxNOHo8+jO+1E1jnxi6TxISpeDg8UQzeoO l/CoPLFHdS97fTTsIunj4fN4e37GtQoaNq3gPndHu2Qv8OqN6r0tHtqJnRRKhD07tlrC8NdvKeIpG Ke3VHKrq9tfgpRdJPlQQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pNqxH-000tMU-St; Fri, 03 Feb 2023 07:57:55 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pNqxE-000tJv-QH for linux-arm-kernel@lists.infradead.org; Fri, 03 Feb 2023 07:57:54 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675411070; 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: content-transfer-encoding:content-transfer-encoding; bh=g21Iu8+5kTCHxV/HcDCZ+GcaGo0EEWHvhzSWCcuB1DY=; b=HREdT1j0xB/buL0HU5twS4vdJ6sG5eZJ1UZnD9fZT+9JvdUQQUidLp32/iyJYBWFin2dLL +6rHlo1CzuaglXYjRf5l0eqDmRdL/751sYZ+gLOJOSMxIzMthQDv6xKRA6gXDN1V37lq1s G99+vCTOkwtrlCzF/5alGdenh+wLOlU= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-594-rEZWSSTyOMWL2OBs7XjtMA-1; Fri, 03 Feb 2023 02:57:39 -0500 X-MC-Unique: rEZWSSTyOMWL2OBs7XjtMA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id DC69129DD991; Fri, 3 Feb 2023 07:57:38 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (ovpn-12-127.pek2.redhat.com [10.72.12.127]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2246A404CD80; Fri, 3 Feb 2023 07:57:34 +0000 (UTC) From: Baoquan He To: linux-kernel@vger.kernel.org Cc: kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, horms@kernel.org, thunder.leizhen@huawei.com, John.p.donnelly@oracle.com, will@kernel.org, Baoquan He Subject: [PATCH v2] arm64: kdump: simplify the reservation behaviour of crashkernel=,high Date: Fri, 3 Feb 2023 15:57:23 +0800 Message-Id: <20230203075723.114538-1-bhe@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230202_235752_956382_B7BC5518 X-CRM114-Status: GOOD ( 21.39 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On arm64, reservation for 'crashkernel=xM,high' is taken by searching for suitable memory region top down. If the 'xM' of crashkernel high memory is reserved from high memory successfully, it will try to reserve crashkernel low memory later accoringly. Otherwise, it will try to search low memory area for the 'xM' suitable region. Please see the details in Documentation/admin-guide/kernel-parameters.txt. While we observed an unexpected case where a reserved region crosses the high and low meomry boundary. E.g on a system with 4G as low memory end, user added the kernel parameters like: 'crashkernel=512M,high', it could finally have [4G-126M, 4G+386M], [1G, 1G+128M] regions in running kernel. The crossing 4G boudary of crashkernel high region will bring issues: 1) For crashkernel=x,high, if getting crashkernel high region across 4G boudary, then user will see two memory regions under 4G, and one memory region above 4G. The two crashkernel low memory regions are confusing. 2) If people explicityly specify "crashkernel=x,high crashkernel=y,low" and y <= 128M, when crashkernel high region crosses 4G boudary and the part below 4G of crashkernel high reservation is bigger than y, the expected crahskernel low reservation will be skipped. But the expected crashkernel high reservation is shrank and could not satisfy user space requirement. 3) The crossing boundary behaviour of crahskernel high reservation is different than x86 arch. On x86_64, the memory near 4G is reserved by system, e.g for mapping firmware, pci map. The crashkernel reservation crossing 4G boundary never happens. From distros point of view, this brings inconsistency and confusion. Users need to dig into x86 and arm64 details to find out why. For kernel itself, the impact of issue 3) could be slight. While issue 1) and 2) cause actual impact becuase it brings obscure semantics and behaviour to crashkernel=,high reservation. Here, for crashkernel=xM,high, search the high memory for the suitable region only in high memory. If failed, try reserving the suitable region only in low memory. Like this, the crashkernel high region will only exist in high memory, and crashkernel low region only exists in low memory. The reservation behaviour for crashkernel=,high is clearer and simpler. Signed-off-by: Baoquan He --- v1->v2: - Fold patch 2 of v1 into patch 1 for better reviewing. - Update patch log to add more details. arch/arm64/mm/init.c | 43 +++++++++++++++++++++++++++++++++---------- 1 file changed, 33 insertions(+), 10 deletions(-) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 58a0bb2c17f1..b8cb780df0cb 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -127,12 +127,13 @@ static int __init reserve_crashkernel_low(unsigned long long low_size) */ static void __init reserve_crashkernel(void) { - unsigned long long crash_base, crash_size; - unsigned long long crash_low_size = 0; + unsigned long long crash_base, crash_size, search_base; unsigned long long crash_max = CRASH_ADDR_LOW_MAX; + unsigned long long crash_low_size = 0; char *cmdline = boot_command_line; - int ret; bool fixed_base = false; + bool high = false; + int ret; if (!IS_ENABLED(CONFIG_KEXEC_CORE)) return; @@ -155,7 +156,9 @@ static void __init reserve_crashkernel(void) else if (ret) return; + search_base = CRASH_ADDR_LOW_MAX; crash_max = CRASH_ADDR_HIGH_MAX; + high = true; } else if (ret || !crash_size) { /* The specified value is invalid */ return; @@ -166,31 +169,51 @@ static void __init reserve_crashkernel(void) /* User specifies base address explicitly. */ if (crash_base) { fixed_base = true; + search_base = crash_base; crash_max = crash_base + crash_size; } retry: crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, - crash_base, crash_max); + search_base, crash_max); if (!crash_base) { /* - * If the first attempt was for low memory, fall back to - * high memory, the minimum required low memory will be - * reserved later. + * For crashkernel=size[KMG]@offset[KMG], print out failure + * message if can't reserve the specified region. */ - if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) { + if (fixed_base) { + pr_info("crashkernel reservation failed - memory is in use.\n"); + return; + } + + /* + * For crashkernel=size[KMG], if the first attempt was for + * low memory, fall back to high memory, the minimum required + * low memory will be reserved later. + */ + if (!high && crash_max == CRASH_ADDR_LOW_MAX) { crash_max = CRASH_ADDR_HIGH_MAX; + search_base = CRASH_ADDR_LOW_MAX; crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; goto retry; } + /* + * For crashkernel=size[KMG],high, if the first attempt was + * for high memory, fall back to low memory. + */ + if (high && crash_max == CRASH_ADDR_HIGH_MAX) { + crash_max = CRASH_ADDR_LOW_MAX; + search_base = 0; + goto retry; + } pr_warn("cannot allocate crashkernel (size:0x%llx)\n", crash_size); return; } - if ((crash_base > CRASH_ADDR_LOW_MAX - crash_low_size) && - crash_low_size && reserve_crashkernel_low(crash_low_size)) { + if ((crash_base >= CRASH_ADDR_LOW_MAX) && crash_low_size && + reserve_crashkernel_low(crash_low_size)) { memblock_phys_free(crash_base, crash_size); return; }