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Wed, 12 Jan 2022 09:50:37 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1C5C14C050; Wed, 12 Jan 2022 09:50:37 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7A5A34C04E; Wed, 12 Jan 2022 09:50:32 +0000 (GMT) Received: from [9.163.9.101] (unknown [9.163.9.101]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 12 Jan 2022 09:50:31 +0000 (GMT) Message-ID: <4eafb016-8b80-dae5-cd93-69adca33bfb7@linux.ibm.com> Date: Wed, 12 Jan 2022 15:20:29 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH 1/2] mm/cma: provide option to opt out from exposing pages on activation failure Content-Language: en-US To: David Hildenbrand , akpm@linux-foundation.org, linux-mm@kvack.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org Cc: osalvador@suse.de, mahesh@linux.ibm.com, sourabhjain@linux.ibm.com, mike.kravetz@oracle.com References: <20211220193419.104242-1-hbathini@linux.ibm.com> <20211220193419.104242-2-hbathini@linux.ibm.com> <21364354-83d1-5a56-378e-8ca07ccf9957@redhat.com> From: Hari Bathini In-Reply-To: <21364354-83d1-5a56-378e-8ca07ccf9957@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: Izr7lUSFYi7ivtarlHQOEdYZwe3jNepZ X-Proofpoint-ORIG-GUID: _q2cqel33x_f-hYUMaJgZ06jRn8GVq3W X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-01-12_03,2022-01-11_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 mlxlogscore=999 clxscore=1015 spamscore=0 phishscore=0 bulkscore=0 priorityscore=1501 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2201120061 X-Rspamd-Queue-Id: F07861C000B X-Stat-Signature: pujzeroxkofxirsuei4nisqmu5dc83w3 Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=cdl1uwFC; spf=pass (imf18.hostedemail.com: domain of hbathini@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=hbathini@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com X-Rspamd-Server: rspam07 X-HE-Tag: 1641981047-736216 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11/01/22 8:06 pm, David Hildenbrand wrote: > On 06.01.22 13:01, Hari Bathini wrote: >> >> To answer the question, fadump does not want the memory to be used for >> kernel pages, if CMA activation fails... > > Okay, so what you want is a reserved region, and if possible, let CMA > use that memory for other (movable allocation) purposes until you > actually need that area and free it up by using CMA. If CMA cannot use > the region because of zone issues, you just want that region to stay > reserved. > Right. > I guess the biggest different to other CMA users is that it can make use > of the memory even if not allocated via CMA -- because it's going to > make use of the the physical memory range indirectly via a HW facility, > not via any "struct page" access. > > > I wonder if we can make the terminology a bit clearer, the freeing part > is a bit confusing, because init_cma_reserved_pageblock() essentially > also frees pages, just to the MIGRATE_CMA lists ... what you want is to > treat it like a simple memblock allocation/reservation on error. > What about: > * cma->reserve_pages_on_error that defaults to false > * void __init cma_reserve_pages_on_error(struct cma *cma) Yeah, this change does make things bit more clearer. Will send out a v2 with the change..