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Thu, 17 Oct 2024 09:54:00 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 93E0A20043; Thu, 17 Oct 2024 09:54:00 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7BFCE20040; Thu, 17 Oct 2024 09:53:59 +0000 (GMT) Received: from li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com (unknown [9.179.26.155]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTPS; Thu, 17 Oct 2024 09:53:59 +0000 (GMT) Date: Thu, 17 Oct 2024 11:53:58 +0200 From: Alexander Gordeev To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, virtualization@lists.linux.dev, linux-doc@vger.kernel.org, kvm@vger.kernel.org, Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Thomas Huth , Cornelia Huck , Janosch Frank , Claudio Imbrenda , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Andrew Morton , Jonathan Corbet , Mario Casquero Subject: Re: [PATCH v2 4/7] s390/physmem_info: query diag500(STORAGE LIMIT) to support QEMU/KVM memory devices Message-ID: References: <20241014144622.876731-1-david@redhat.com> <20241014144622.876731-5-david@redhat.com> <04d5169f-3289-4aac-abca-90b20ad4e9c9@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <04d5169f-3289-4aac-abca-90b20ad4e9c9@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: rsW7nei5PMxsFNxCpTTeWNX0xwVxfCqF X-Proofpoint-GUID: G8r6oOg0lIoIYHzFUNbBTccmQlmMrzuo X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 suspectscore=0 malwarescore=0 spamscore=0 lowpriorityscore=0 phishscore=0 mlxscore=0 clxscore=1015 adultscore=0 priorityscore=1501 mlxlogscore=282 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2410170064 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C9F8418000C X-Stat-Signature: eo96j3waqoyx5ofqejf6847bqmdkpjk7 X-Rspam-User: X-HE-Tag: 1729158845-602649 X-HE-Meta: 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 IMkWTrc+ V5YwgOhvP0L/A0TI9MVLC/HgTBfXxfRSeA2hTPiy9Bo8OiQnJw+tQ0ptzVW1AqIUhwjfX+/2KwI9TV5mRroC/ql2hlEr8Ayx9SWLvX8BCVM6pv2viCApey/37qNJJwDaaqjAUZ+shabhqLE06kGr6ejvxPb88pg66KWTGWex0wkfMwb+FwEe19V91oo6vt4/s5vek1Q6dZvS0c4Lc8cM/nq5mU2jpQaaDelI2pPm+oQNA6wx0huQG98YkeGvTQMESkDZq4IoLNG88xPzRYdiGerh/p20pZNMpQOPtidUSGoCrpxgfUJXJ8yQE0mu7NMBct5alPi1NpwADgxiQYsk+OC2k6CF1oYXzv1FZsrVHfrYckvjxEiXj/TEjsazdLw2rUAlYca/AhtczdiVwScucfGkcBg== 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: List-Subscribe: List-Unsubscribe: > > Why search_mem_end() is not tried in case sclp_early_get_memsize() failed? > > Patch #3 documents that: > > + The storage limit does not indicate currently usable storage, it may > + include holes, standby storage and areas reserved for other means, such > + as memory hotplug or virtio-mem devices. Other interfaces for detecting > + actually usable storage, such as SCLP, must be used in conjunction with > + this subfunction. Yes, I read this and that exactly what causes my confusion. In this wording it sounds like SCLP *or* other methods are fine to use. But then you use SCLP or DIAGNOSE 260, but not memory scanning. So I am still confused ;) > If SCLP would fail, something would be seriously wrong and we should just crash > instead of trying to fallback to the legacy way of scanning. But what is wrong with the legacy way of scanning? > > > + case MEM_DETECT_DIAG500_STOR_LIMIT: > > > + return "diag500 storage limit"; > > > > AFAIU you want to always override MEM_DETECT_DIAG500_STOR_LIMIT method > > with an online memory detection method. In that case this code is dead. > > Not in the above case, pathological case above where something went wrong > during sclp_early_get_memsize(). In that scenario, die_oom() would indicate > that there are no memory ranges but that "diag500 storage limit" worked. > > Does that make sense? Yes, I get your approach. > Thanks for the review! Thanks! > -- > Cheers, > > David / dhildenb