From nobody Mon Sep 15 01:54:09 2025 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 659D1C6379F for ; Tue, 17 Jan 2023 03:50:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235518AbjAQDug (ORCPT ); Mon, 16 Jan 2023 22:50:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46848 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235362AbjAQDu2 (ORCPT ); Mon, 16 Jan 2023 22:50:28 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AEFD923106 for ; Mon, 16 Jan 2023 19:49:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673927378; 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: in-reply-to:in-reply-to:references:references; bh=XKf0pfjvYxPkjbdKZXYck8pY3VTnEaZbMJ46YyM2HTg=; b=OSAAvxPM1H5kZyfrebopvU0/mI9/cwdvMw7Czi5zankb4AXwDXTUj0xXPaukKvBr0PNhZb BQhigRws67z9sm/3aL0sJwSzm+YPDDoRuUCzPCY8AiNFjpfw+u/AG+W7eYm9clqDvW3vgC mdFB+3Jv+C4gl6Ul6Mb4zLq/6YFZ2GA= 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-482-0KrDAEoOOSGLbtIy3AN8Hg-1; Mon, 16 Jan 2023 22:49:35 -0500 X-MC-Unique: 0KrDAEoOOSGLbtIy3AN8Hg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0D407802BF3; Tue, 17 Jan 2023 03:49:35 +0000 (UTC) Received: from fedora.redhat.com (ovpn-12-229.pek2.redhat.com [10.72.12.229]) by smtp.corp.redhat.com (Postfix) with ESMTP id A08321415108; Tue, 17 Jan 2023 03:49:30 +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, will@kernel.org, thunder.leizhen@huawei.com, John.p.donnelly@oracle.com, wangkefeng.wang@huawei.com, Baoquan He Subject: [PATCH 1/2] arm64: kdump: simplify the reservation behaviour of crashkernel=,high Date: Tue, 17 Jan 2023 11:49:20 +0800 Message-Id: <20230117034921.185150-2-bhe@redhat.com> In-Reply-To: <20230117034921.185150-1-bhe@redhat.com> References: <20230117034921.185150-1-bhe@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" On arm64, reservation for 'crashkernel=3DxM,high' is taken by searching for suitable memory region up 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. 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=3D512M,high', it could finally have [4G-126M, 4G+386M], [1G, 1G+128M] regions in running kernel. This looks very strange because we have two low memory regions [4G-126M, 4G] and [1G, 1G+128M]. Much explanation need be given to tell why that happened. Here, for crashkernel=3DxM,high, search the high memory for the suitable region above the high and low memory boundary. If failed, try reserving the suitable region below the boundary. 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=3D,high is clearer and simpler. Signed-off-by: Baoquan He --- arch/arm64/mm/init.c | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 58a0bb2c17f1..26a05af2bfa8 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -127,12 +127,13 @@ static int __init reserve_crashkernel_low(unsigned lo= ng long low_size) */ static void __init reserve_crashkernel(void) { - unsigned long long crash_base, crash_size; - unsigned long long crash_low_size =3D 0; + unsigned long long crash_base, crash_size, search_base; unsigned long long crash_max =3D CRASH_ADDR_LOW_MAX; + unsigned long long crash_low_size =3D 0; char *cmdline =3D boot_command_line; - int ret; bool fixed_base =3D false; + bool high =3D false; + int ret; =20 if (!IS_ENABLED(CONFIG_KEXEC_CORE)) return; @@ -155,7 +156,9 @@ static void __init reserve_crashkernel(void) else if (ret) return; =20 + search_base =3D CRASH_ADDR_LOW_MAX; crash_max =3D CRASH_ADDR_HIGH_MAX; + high =3D true; } else if (ret || !crash_size) { /* The specified value is invalid */ return; @@ -166,31 +169,44 @@ static void __init reserve_crashkernel(void) /* User specifies base address explicitly. */ if (crash_base) { fixed_base =3D true; + search_base =3D crash_base; crash_max =3D crash_base + crash_size; } =20 retry: crash_base =3D memblock_phys_alloc_range(crash_size, CRASH_ALIGN, - crash_base, crash_max); + search_base, crash_max); if (!crash_base) { + if (fixed_base) { + pr_warn("cannot reserve crashkernel region [0x%llx-0x%llx]\n", + search_base, crash_max); + return; + } + /* * If the first attempt was for low memory, fall back to * high memory, the minimum required low memory will be * reserved later. */ - if (!fixed_base && (crash_max =3D=3D CRASH_ADDR_LOW_MAX)) { + if (!high && crash_max =3D=3D CRASH_ADDR_LOW_MAX) { crash_max =3D CRASH_ADDR_HIGH_MAX; + search_base =3D CRASH_ADDR_LOW_MAX; crash_low_size =3D DEFAULT_CRASH_KERNEL_LOW_SIZE; goto retry; } =20 + if (high && (crash_max =3D=3D CRASH_ADDR_HIGH_MAX)) { + crash_max =3D CRASH_ADDR_LOW_MAX; + search_base =3D 0; + goto retry; + } pr_warn("cannot allocate crashkernel (size:0x%llx)\n", crash_size); return; } =20 - if ((crash_base > CRASH_ADDR_LOW_MAX - crash_low_size) && - crash_low_size && reserve_crashkernel_low(crash_low_size)) { + if ((crash_base >=3D CRASH_ADDR_LOW_MAX) && crash_low_size && + reserve_crashkernel_low(crash_low_size)) { memblock_phys_free(crash_base, crash_size); return; } --=20 2.34.1 From nobody Mon Sep 15 01:54:09 2025 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 45A9DC6379F for ; Tue, 17 Jan 2023 03:50:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235536AbjAQDuq (ORCPT ); Mon, 16 Jan 2023 22:50:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46694 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235501AbjAQDuf (ORCPT ); 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Mon, 16 Jan 2023 22:49:41 -0500 X-MC-Unique: upN5m9UrNDW622U8L_BpjQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CA8EA101A52E; Tue, 17 Jan 2023 03:49:40 +0000 (UTC) Received: from fedora.redhat.com (ovpn-12-229.pek2.redhat.com [10.72.12.229]) by smtp.corp.redhat.com (Postfix) with ESMTP id D146A14171B8; Tue, 17 Jan 2023 03:49:35 +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, will@kernel.org, thunder.leizhen@huawei.com, John.p.donnelly@oracle.com, wangkefeng.wang@huawei.com, Baoquan He Subject: [PATCH 2/2] arm64/kdump: add code comments for crashkernel reservation cases Date: Tue, 17 Jan 2023 11:49:21 +0800 Message-Id: <20230117034921.185150-3-bhe@redhat.com> In-Reply-To: <20230117034921.185150-1-bhe@redhat.com> References: <20230117034921.185150-1-bhe@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This will help understand codes on crashkernel reservations on arm64. Signed-off-by: Baoquan He --- arch/arm64/mm/init.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 26a05af2bfa8..f88ad17cb20d 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -177,6 +177,10 @@ static void __init reserve_crashkernel(void) crash_base =3D memblock_phys_alloc_range(crash_size, CRASH_ALIGN, search_base, crash_max); if (!crash_base) { + /* + * For crashkernel=3Dsize[KMG]@offset[KMG], print out failure + * message if can't reserve the specified region. + */ if (fixed_base) { pr_warn("cannot reserve crashkernel region [0x%llx-0x%llx]\n", search_base, crash_max); @@ -188,6 +192,11 @@ static void __init reserve_crashkernel(void) * high memory, the minimum required low memory will be * reserved later. */ + /* + * For crashkernel=3Dsize[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 =3D=3D CRASH_ADDR_LOW_MAX) { crash_max =3D CRASH_ADDR_HIGH_MAX; search_base =3D CRASH_ADDR_LOW_MAX; @@ -195,6 +204,10 @@ static void __init reserve_crashkernel(void) goto retry; } =20 + /* + * For crashkernel=3Dsize[KMG],high, if the first attempt was for + * high memory, fall back to low memory. + */ if (high && (crash_max =3D=3D CRASH_ADDR_HIGH_MAX)) { crash_max =3D CRASH_ADDR_LOW_MAX; search_base =3D 0; --=20 2.34.1