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Tue, 30 Jun 2020 06:11:05 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 05U6B32l49872896 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 30 Jun 2020 06:11:03 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3D9E752050; Tue, 30 Jun 2020 06:11:03 +0000 (GMT) Received: from [9.102.2.126] (unknown [9.102.2.126]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 1E51D52051; Tue, 30 Jun 2020 06:10:59 +0000 (GMT) Subject: Re: [PATCH 04/11] ppc64/kexec_file: avoid stomping memory used by special regions To: piliu , Michael Ellerman , Andrew Morton References: <159319825403.16351.7253978047621755765.stgit@hbathini.in.ibm.com> <159319831192.16351.17443438699302756548.stgit@hbathini.in.ibm.com> <9cfda789-0747-a67a-b825-5ea6f15099b8@redhat.com> <283fc181-2331-7c2f-db66-5e02e5ffb2e4@redhat.com> From: Hari Bathini Message-ID: Date: Tue, 30 Jun 2020 11:40:59 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <283fc181-2331-7c2f-db66-5e02e5ffb2e4@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-06-30_01:2020-06-30, 2020-06-29 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=0 mlxlogscore=999 lowpriorityscore=0 spamscore=0 priorityscore=1501 phishscore=0 suspectscore=0 adultscore=0 cotscore=-2147483648 bulkscore=0 clxscore=1015 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006300046 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kexec-ml , Petr Tesarik , Mahesh J Salgaonkar , Sourabh Jain , lkml , linuxppc-dev , Mimi Zohar , Vivek Goyal , Dave Young , Thiago Jung Bauermann , Eric Biederman Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 30/06/20 9:00 am, piliu wrote: > > > On 06/29/2020 01:55 PM, Hari Bathini wrote: >> >> >> On 28/06/20 7:44 am, piliu wrote: >>> Hi Hari, >> >> Hi Pingfan, >> >>> >>> After a quick through for this series, I have a few question/comment on >>> this patch for the time being. Pls see comment inline. >>> >>> On 06/27/2020 03:05 AM, Hari Bathini wrote: >>>> crashkernel region could have an overlap with special memory regions >>>> like opal, rtas, tce-table & such. These regions are referred to as >>>> exclude memory ranges. Setup this ranges during image probe in order >>>> to avoid them while finding the buffer for different kdump segments. >> >> [...] >> >>>> + /* >>>> + * Use the locate_mem_hole logic in kexec_add_buffer() for regular >>>> + * kexec_file_load syscall >>>> + */ >>>> + if (kbuf->image->type != KEXEC_TYPE_CRASH) >>>> + return 0; >>> Can the ranges overlap [crashk_res.start, crashk_res.end]? Otherwise >>> there is no requirement for @exclude_ranges. >> >> The ranges like rtas, opal are loaded by f/w. They almost always overlap with >> crashkernel region. So, @exclude_ranges is required to support kdump. > f/w passes rtas/opal as service, then must f/w mark these ranges as > fdt_reserved_mem in order to make kernel aware not to use these ranges? It does. Actually, reserve_map + reserved-ranges are reserved as soon as memblock allocator is ready but not before crashkernel reservation. Check early_reserve_mem() call in kernel/prom.c > Otherwise kernel memory allocation besides kdump can also overwrite > these ranges.> > Hmm, revisiting reserve_crashkernel(). It seems not to take any reserved > memory into consider except kernel text. Could it work based on memblock > allocator? So, kdump could possibly overwrite these regions which is why an exclude range list is needed. Same thing was done in kexec-tools as well. Thanks Hari