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=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED 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 54B18C433E2 for ; Tue, 2 Jun 2020 14:42:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22F372068D for ; Tue, 2 Jun 2020 14:42:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="EH0abBKq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728202AbgFBOmx (ORCPT ); Tue, 2 Jun 2020 10:42:53 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:35192 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725919AbgFBOmw (ORCPT ); Tue, 2 Jun 2020 10:42:52 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 052EfvdT009136; Tue, 2 Jun 2020 14:42:10 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=content-type : mime-version : subject : from : in-reply-to : date : cc : content-transfer-encoding : message-id : references : to; s=corp-2020-01-29; bh=f27y03fv745c02yIbYexRAAwPCBiWvLJPcvvXS3z+xM=; b=EH0abBKqZG1gX4ZmZVAkyesz9yZtGV/Wxw+m8+aVic6drI2msG3P3lWpaymd+PGaLLin Js91irIvCtJJCH8Jb2BYC0nQyQsrbJCOTEoBIIjLMb9PBhj0a20r69IyI5sPxrXZGRDX CwZhHmWoblfiPbn7cH6Rnp35fbOR3L38RfTtjuNSOUYb9zmtN2vK93BEPyFBVDhNAsjK Io8dMBxCHZq0pIaZ1x+9Eldka0ks9kKAAz/gm5+QtGc1uL39wOzR40FyRkneU96Qdc2g F13UHMwD2v4fwSTnVicwjGX4ghqWPwHDfI8m0uI1ZcQoFkOo3GZLE8jDfgY3041XDAdF 3w== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by userp2130.oracle.com with ESMTP id 31bewqvfwm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 02 Jun 2020 14:42:10 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 052EXHBY038281; Tue, 2 Jun 2020 14:42:09 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3030.oracle.com with ESMTP id 31c1dxbhwn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 02 Jun 2020 14:42:09 +0000 Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 052Eg0sC006406; Tue, 2 Jun 2020 14:42:00 GMT Received: from dhcp-10-154-181-125.vpn.oracle.com (/10.154.181.125) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 02 Jun 2020 07:42:00 -0700 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\)) Subject: Re: [PATCH v8 0/5] support reserving crashkernel above 4G on arm64 kdump From: John Donnelly In-Reply-To: Date: Tue, 2 Jun 2020 09:41:58 -0500 Cc: Bhupesh Sharma , Chen Zhou , Simon Horman , Devicetree List , Baoquan He , Will Deacon , Linux Doc Mailing List , Catalin Marinas , kexec mailing list , Linux Kernel Mailing List , Rob Herring , Ingo Molnar , Arnd Bergmann , guohanjun@huawei.com, James Morse , Thomas Gleixner , Prabhakar Kushwaha , RuiRui Yang , linux-arm-kernel Content-Transfer-Encoding: quoted-printable Message-Id: <6EA47B07-5119-49DF-9980-12A2066F22CA@oracle.com> References: <20200521093805.64398-1-chenzhou10@huawei.com> <303695cc-d3ea-9f51-1489-07d27d4253d4@oracle.com> To: Prabhakar Kushwaha X-Mailer: Apple Mail (2.3445.9.1) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9640 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 mlxlogscore=999 spamscore=0 bulkscore=0 adultscore=0 suspectscore=1 mlxscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006020104 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9640 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 bulkscore=0 phishscore=0 suspectscore=1 impostorscore=0 cotscore=-2147483648 lowpriorityscore=0 mlxscore=0 adultscore=0 spamscore=0 mlxlogscore=999 malwarescore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006020105 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jun 2, 2020, at 12:38 AM, Prabhakar Kushwaha = wrote: >=20 > On Tue, Jun 2, 2020 at 3:29 AM John Donnelly = wrote: >>=20 >> Hi . See below ! >>=20 >>> On Jun 1, 2020, at 4:02 PM, Bhupesh Sharma = wrote: >>>=20 >>> Hi John, >>>=20 >>> On Tue, Jun 2, 2020 at 1:01 AM John Donnelly = wrote: >>>>=20 >>>> Hi, >>>>=20 >>>>=20 >>>> On 6/1/20 7:02 AM, Prabhakar Kushwaha wrote: >>>>> Hi Chen, >>>>>=20 >>>>> On Thu, May 21, 2020 at 3:05 PM Chen Zhou = wrote: >>>>>> This patch series enable reserving crashkernel above 4G in arm64. >>>>>>=20 >>>>>> There are following issues in arm64 kdump: >>>>>> 1. We use crashkernel=3DX to reserve crashkernel below 4G, which = will fail >>>>>> when there is no enough low memory. >>>>>> 2. Currently, crashkernel=3DY@X can be used to reserve = crashkernel above 4G, >>>>>> in this case, if swiotlb or DMA buffers are required, crash dump = kernel >>>>>> will boot failure because there is no low memory available for = allocation. >>>>>>=20 >>>>>> To solve these issues, introduce crashkernel=3DX,low to reserve = specified >>>>>> size low memory. >>>>>> Crashkernel=3DX tries to reserve memory for the crash dump kernel = under >>>>>> 4G. If crashkernel=3DY,low is specified simultaneously, reserve = spcified >>>>>> size low memory for crash kdump kernel devices firstly and then = reserve >>>>>> memory above 4G. >>>>>>=20 >>>>>> When crashkernel is reserved above 4G in memory, that is, = crashkernel=3DX,low >>>>>> is specified simultaneously, kernel should reserve specified size = low memory >>>>>> for crash dump kernel devices. So there may be two crash kernel = regions, one >>>>>> is below 4G, the other is above 4G. >>>>>> In order to distinct from the high region and make no effect to = the use of >>>>>> kexec-tools, rename the low region as "Crash kernel (low)", and = add DT property >>>>>> "linux,low-memory-range" to crash dump kernel's dtb to pass the = low region. >>>>>>=20 >>>>>> Besides, we need to modify kexec-tools: >>>>>> arm64: kdump: add another DT property to crash dump kernel's = dtb(see [1]) >>>>>>=20 >>>>>> The previous changes and discussions can be retrieved from: >>>>>>=20 >>>>>> Changes since [v7] >>>>>> - Move x86 CRASH_ALIGN to 2M >>>>>> Suggested by Dave and do some test, move x86 CRASH_ALIGN to 2M. >>>>>> - Update Documentation/devicetree/bindings/chosen.txt >>>>>> Add corresponding documentation to = Documentation/devicetree/bindings/chosen.txt suggested by Arnd. >>>>>> - Add Tested-by from Jhon and pk >>>>>>=20 >>>>>> Changes since [v6] >>>>>> - Fix build errors reported by kbuild test robot. >>>>>>=20 >>>>>> Changes since [v5] >>>>>> - Move reserve_crashkernel_low() into kernel/crash_core.c. >>>>>> - Delete crashkernel=3DX,high. >>>>>> - Modify crashkernel=3DX,low. >>>>>> If crashkernel=3DX,low is specified simultaneously, reserve = spcified size low >>>>>> memory for crash kdump kernel devices firstly and then reserve = memory above 4G. >>>>>> In addition, rename crashk_low_res as "Crash kernel (low)" for = arm64, and then >>>>>> pass to crash dump kernel by DT property = "linux,low-memory-range". >>>>>> - Update Documentation/admin-guide/kdump/kdump.rst. >>>>>>=20 >>>>>> Changes since [v4] >>>>>> - Reimplement memblock_cap_memory_ranges for multiple ranges by = Mike. >>>>>>=20 >>>>>> Changes since [v3] >>>>>> - Add memblock_cap_memory_ranges back for multiple ranges. >>>>>> - Fix some compiling warnings. >>>>>>=20 >>>>>> Changes since [v2] >>>>>> - Split patch "arm64: kdump: support reserving crashkernel above = 4G" as >>>>>> two. Put "move reserve_crashkernel_low() into kexec_core.c" in a = separate >>>>>> patch. >>>>>>=20 >>>>>> Changes since [v1]: >>>>>> - Move common reserve_crashkernel_low() code into = kernel/kexec_core.c. >>>>>> - Remove memblock_cap_memory_ranges() i added in v1 and implement = that >>>>>> in fdt_enforce_memory_region(). >>>>>> There are at most two crash kernel regions, for two crash kernel = regions >>>>>> case, we cap the memory range [min(regs[*].start), = max(regs[*].end)] >>>>>> and then remove the memory range in the middle. >>>>>>=20 >>>>>> [1]: = https://urldefense.com/v3/__http://lists.infradead.org/pipermail/kexec/202= 0-May/025128.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3K= RVqALmvSK2VmCkIPIhsaxbvpn1uM1$ >>>>>> [v1]: = https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/2/1174__;!!GqivPV= a7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbt0xN9P= E$ >>>>>> [v2]: = https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/9/86__;!!GqivPVa7= Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbub7yUQH$= >>>>>> [v3]: = https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/9/306__;!!GqivPVa= 7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbnc4zPPV= $ >>>>>> [v4]: = https://urldefense.com/v3/__https://lkml.org/lkml/2019/4/15/273__;!!GqivPV= a7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbvsAsZL= u$ >>>>>> [v5]: = https://urldefense.com/v3/__https://lkml.org/lkml/2019/5/6/1360__;!!GqivPV= a7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbl24n-7= 9$ >>>>>> [v6]: = https://urldefense.com/v3/__https://lkml.org/lkml/2019/8/30/142__;!!GqivPV= a7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbs7r8G2= a$ >>>>>> [v7]: = https://urldefense.com/v3/__https://lkml.org/lkml/2019/12/23/411__;!!GqivP= Va7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvSK2VmCkIPIhsaxbiFUH9= 0G$ >>>>>>=20 >>>>>> Chen Zhou (5): >>>>>> x86: kdump: move reserve_crashkernel_low() into crash_core.c >>>>>> arm64: kdump: reserve crashkenel above 4G for crash dump kernel >>>>>> arm64: kdump: add memory for devices by DT property, = low-memory-range >>>>>> kdump: update Documentation about crashkernel on arm64 >>>>>> dt-bindings: chosen: Document linux,low-memory-range for arm64 = kdump >>>>>>=20 >>>>> We are getting "warn_alloc" [1] warning during boot of kdump = kernel >>>>> with bootargs as [2] of primary kernel. >>>>> This error observed on ThunderX2 ARM64 platform. >>>>>=20 >>>>> It is observed with latest upstream tag (v5.7-rc3) with this patch = set >>>>> and = https://urldefense.com/v3/__https://lists.infradead.org/pipermail/kexec/20= 20-May/025128.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3= KRVqALmvSK2VmCkIPIhsaxbiIAAlzu$ >>>>> Also **without** this patch-set >>>>> = "https://urldefense.com/v3/__https://www.spinics.net/lists/arm-kernel/msg8= 06882.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmv= SK2VmCkIPIhsaxbjC6ujMA$" >>>>>=20 >>>>> This issue comes whenever crashkernel memory is reserved after = 0xc000_0000. >>>>> More details discussed earlier in >>>>> = https://urldefense.com/v3/__https://www.spinics.net/lists/arm-kernel/msg80= 6882.html__;!!GqivPVa7Brio!LnTSARkCt0V0FozR0KmqooaH5ADtdXvs3mPdP3KRVqALmvS= K2VmCkIPIhsaxbjC6ujMA$ without any >>>>> solution >>>>>=20 >>>>> This patch-set is expected to solve similar kind of issue. >>>>> i.e. low memory is only targeted for DMA, swiotlb; So above = mentioned >>>>> observation should be considered/fixed. . >>>>>=20 >>>>> --pk >>>>>=20 >>>>> [1] >>>>> [ 30.366695] DMI: Cavium Inc. Saber/Saber, BIOS >>>>> TX2-FW-Release-3.1-build_01-2803-g74253a541a mm/dd/yyyy >>>>> [ 30.367696] NET: Registered protocol family 16 >>>>> [ 30.369973] swapper/0: page allocation failure: order:6, >>>>> mode:0x1(GFP_DMA), nodemask=3D(null),cpuset=3D/,mems_allowed=3D0 >>>>> [ 30.369980] CPU: 0 PID: 1 Comm: swapper/0 Not tainted = 5.7.0-rc3+ #121 >>>>> [ 30.369981] Hardware name: Cavium Inc. Saber/Saber, BIOS >>>>> TX2-FW-Release-3.1-build_01-2803-g74253a541a mm/dd/yyyy >>>>> [ 30.369984] Call trace: >>>>> [ 30.369989] dump_backtrace+0x0/0x1f8 >>>>> [ 30.369991] show_stack+0x20/0x30 >>>>> [ 30.369997] dump_stack+0xc0/0x10c >>>>> [ 30.370001] warn_alloc+0x10c/0x178 >>>>> [ 30.370004] __alloc_pages_slowpath.constprop.111+0xb10/0xb50 >>>>> [ 30.370006] __alloc_pages_nodemask+0x2b4/0x300 >>>>> [ 30.370008] alloc_page_interleave+0x24/0x98 >>>>> [ 30.370011] alloc_pages_current+0xe4/0x108 >>>>> [ 30.370017] dma_atomic_pool_init+0x44/0x1a4 >>>>> [ 30.370020] do_one_initcall+0x54/0x228 >>>>> [ 30.370027] kernel_init_freeable+0x228/0x2cc >>>>> [ 30.370031] kernel_init+0x1c/0x110 >>>>> [ 30.370034] ret_from_fork+0x10/0x18 >>>>> [ 30.370036] Mem-Info: >>>>> [ 30.370064] active_anon:0 inactive_anon:0 isolated_anon:0 >>>>> [ 30.370064] active_file:0 inactive_file:0 isolated_file:0 >>>>> [ 30.370064] unevictable:0 dirty:0 writeback:0 unstable:0 >>>>> [ 30.370064] slab_reclaimable:34 slab_unreclaimable:4438 >>>>> [ 30.370064] mapped:0 shmem:0 pagetables:14 bounce:0 >>>>> [ 30.370064] free:1537719 free_pcp:219 free_cma:0 >>>>> [ 30.370070] Node 0 active_anon:0kB inactive_anon:0kB >>>>> active_file:0kB inactive_file:0kB unevictable:0kB = isolated(anon):0kB >>>>> isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB shmem:0kB >>>>> shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB = writeback_tmp:0kB >>>>> unstable:0kB all_unreclaimable? no >>>>> [ 30.370073] Node 1 active_anon:0kB inactive_anon:0kB >>>>> active_file:0kB inactive_file:0kB unevictable:0kB = isolated(anon):0kB >>>>> isolated(file):0kB mapped:0kB dirty:0kB writeback:0kB shmem:0kB >>>>> shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB = writeback_tmp:0kB >>>>> unstable:0kB all_unreclaimable? no >>>>> [ 30.370079] Node 0 DMA free:0kB min:0kB low:0kB high:0kB >>>>> reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB >>>>> active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB >>>>> present:128kB managed:0kB mlocked:0kB kernel_stack:0kB = pagetables:0kB >>>>> bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB >>>>> [ 30.370084] lowmem_reserve[]: 0 250 6063 6063 >>>>> [ 30.370090] Node 0 DMA32 free:256000kB min:408kB low:664kB >>>>> high:920kB reserved_highatomic:0KB active_anon:0kB = inactive_anon:0kB >>>>> active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB >>>>> present:269700kB managed:256000kB mlocked:0kB kernel_stack:0kB >>>>> pagetables:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB >>>>> [ 30.370094] lowmem_reserve[]: 0 0 5813 5813 >>>>> [ 30.370100] Node 0 Normal free:5894876kB min:9552kB low:15504kB >>>>> high:21456kB reserved_highatomic:0KB active_anon:0kB = inactive_anon:0kB >>>>> active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB >>>>> present:8388608kB managed:5953112kB mlocked:0kB = kernel_stack:21672kB >>>>> pagetables:56kB bounce:0kB free_pcp:876kB local_pcp:176kB = free_cma:0kB >>>>> [ 30.370104] lowmem_reserve[]: 0 0 0 0 >>>>> [ 30.370107] Node 0 DMA: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB = 0*128kB >>>>> 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB =3D 0kB >>>>> [ 30.370113] Node 0 DMA32: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB = 0*128kB >>>>> 0*256kB 0*512kB 0*1024kB 1*2048kB (M) 62*4096kB (M) =3D 256000kB >>>>> [ 30.370119] Node 0 Normal: 2*4kB (M) 3*8kB (ME) 2*16kB (UE) = 3*32kB >>>>> (UM) 1*64kB (U) 2*128kB (M) 2*256kB (ME) 3*512kB (ME) 3*1024kB = (ME) >>>>> 3*2048kB (UME) 1436*4096kB (M) =3D 5893600kB >>>>> [ 30.370129] Node 0 hugepages_total=3D0 hugepages_free=3D0 >>>>> hugepages_surp=3D0 hugepages_size=3D1048576kB >>>>> [ 30.370130] 0 total pagecache pages >>>>> [ 30.370132] 0 pages in swap cache >>>>> [ 30.370134] Swap cache stats: add 0, delete 0, find 0/0 >>>>> [ 30.370135] Free swap =3D 0kB >>>>> [ 30.370136] Total swap =3D 0kB >>>>> [ 30.370137] 2164609 pages RAM >>>>> [ 30.370139] 0 pages HighMem/MovableOnly >>>>> [ 30.370140] 612331 pages reserved >>>>> [ 30.370141] 0 pages hwpoisoned >>>>> [ 30.370143] DMA: failed to allocate 256 KiB pool for atomic >>>>> coherent allocation >>>>=20 >>>>=20 >>>> During my testing I saw the same error and Chen's solution = corrected it . >>>=20 >>> Which combination you are using on your side? I am using Prabhakar's >>> suggested environment and can reproduce the issue >>> with or without Chen's crashkernel support above 4G patchset. >>>=20 >>> I am also using a ThunderX2 platform with latest makedumpfile code = and >>> kexec-tools (with the suggested patch >>> = ). >>>=20 >>> Thanks, >>> Bhupesh >>=20 >>=20 >> I did this activity 5 months ago and I have moved on to other = activities. My DMA failures were related to PCI devices that could not = be enumerated because low-DMA space was not available when crashkernel = was moved above 4G; I don=E2=80=99t recall the exact platform. >>=20 >>=20 >>=20 >> For this failure , >>=20 >>>>> DMA: failed to allocate 256 KiB pool for atomic >>>>> coherent allocation >>=20 >>=20 >> Is due to : >>=20 >>=20 >> 3618082c >> ("arm64 use both ZONE_DMA and ZONE_DMA32") >>=20 >> With the introduction of ZONE_DMA to support the Raspberry DMA >> region below 1G, the crashkernel is placed in the upper 4G >> ZONE_DMA_32 region. Since the crashkernel does not have access >> to the ZONE_DMA region, it prints out call trace during bootup. >>=20 >> It is due to having this CONFIG item ON : >>=20 >>=20 >> CONFIG_ZONE_DMA=3Dy >>=20 >> Turning off ZONE_DMA fixes a issue and Raspberry PI 4 will >> use the device tree to specify memory below 1G. >>=20 >>=20 >=20 > Disabling ZONE_DMA is temporary solution. We may need proper solution Perhaps the Raspberry platform configuration dependencies need separated = from =E2=80=9Cserver class=E2=80=9D Arm equipment ? Or = auto-configured on boot ? Consult an expert ;-)=20 >=20 >> I would like to see Chen=E2=80=99s feature added , perhaps as = EXPERIMENTAL, so we can get some configuration testing done on it. It = corrects having a DMA zone in low memory while crash-kernel is above = 4GB. This has been going on for a year now. >=20 > I will also like this patch to be added in Linux as early as possible. >=20 > Issue mentioned by me happens with or without this patch. >=20 > This patch-set can consider fixing because it uses low memory for DMA > & swiotlb only. > We can consider restricting crashkernel within the required range like = below >=20 > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > index 7f9e5a6dc48c..bd67b90d35bd 100644 > --- a/kernel/crash_core.c > +++ b/kernel/crash_core.c > @@ -354,7 +354,7 @@ int __init reserve_crashkernel_low(void) > return 0; > } >=20 > - low_base =3D memblock_find_in_range(0, 1ULL << 32, low_size, = CRASH_ALIGN); > + low_base =3D memblock_find_in_range(0,0xc0000000, low_size, = CRASH_ALIGN); > if (!low_base) { > pr_err("Cannot reserve %ldMB crashkernel low memory, > please try smaller size.\n", > (unsigned long)(low_size >> 20)); >=20 >=20 I suspect 0xc0000000 would need to be a CONFIG item and not = hard-coded. =20 =20 > Similar change can be considered for scenario "without" this patch. > But it will decrease memory availability for crashkernel. > Hence increase the failure probability of crashkernel reservation. >=20 > --pk