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(p200300cbc705760062cc24c19dbea2f5.dip0.t-ipconnect.de. [2003:cb:c705:7600:62cc:24c1:9dbe:a2f5]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37d7fa7a2a8sm7055378f8f.3.2024.10.17.05.07.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Oct 2024 05:07:13 -0700 (PDT) Message-ID: <45de474c-9af3-4d71-959f-6dbc223b432b@redhat.com> Date: Thu, 17 Oct 2024 14:07:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/7] s390/physmem_info: query diag500(STORAGE LIMIT) to support QEMU/KVM memory devices From: David Hildenbrand To: Alexander Gordeev 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 , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Andrew Morton , Jonathan Corbet , Mario Casquero References: <20241014144622.876731-1-david@redhat.com> <20241014144622.876731-5-david@redhat.com> <04d5169f-3289-4aac-abca-90b20ad4e9c9@redhat.com> <1c7ef09e-9ba2-488e-a249-4db3f65e077d@redhat.com> Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <1c7ef09e-9ba2-488e-a249-4db3f65e077d@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: kd1tirqjdowm3ie4f7aacfpfax1cmiwn X-Rspamd-Queue-Id: 0A2004000E X-Rspamd-Server: rspam02 X-HE-Tag: 1729166829-767202 X-HE-Meta: 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 9tSnqfeA 0KODSJK9biJS6hfKQ/G/hvJcPqrqE06BmOZ/8ezt83osLkDQ2bdbro4vxBatoJElJNzFeIHJkNGCO7/RF8x5Fx1sZhU/xD2E4ko+POo6pD90ALd4yw0Tv5ZNFUBUlXUOe03WckFmM3/vcsW/TnO9pbEQcP/FB9teHXf7SAC2lxSbyvmh99WUxakRUpsn+jIHUDb6HDyHY1UPgdwrOtdC0ED8Ebz+0EmjUNgkEL6Cs4aIyIRFv5I6owc+URkES5osb2TVK1kN2r5kEIj0VU2f4/KA2sw94p7uIMwLhlJ8Qmz1u9g3OBFn5tPjgTKR7h2LJx66v6JP6ns1U8FHHV7yP2pZNKqD3uo3G3Cv1AUMpZ7K/6nGmNVrNiJ2cKK1gjOqq0iXEjoYLvMpNumL7LNZ9XeGqTWA7wom6RdzqeuqXUIYxH30wI32s5cs3uS2JDCXsLWLz 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: On 17.10.24 12:00, David Hildenbrand wrote: > On 17.10.24 11:53, Alexander Gordeev wrote: >>>> 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 ;) > > Well, DIAGNOSE 260 is z/VM only and DIAG 500 is KVM only. So there are > currently not really any other reasonable ways besides SCLP. Correction: Staring at the code again, in detect_physmem_online_ranges() we will indeed try: a) sclp_early_read_storage_info() b) diag260() But if neither works, we cannot blindly add all that memory, something is messed up. So we'll fallback to c) sclp_early_get_memsize() But if none of that works, something is seriously wrong. I will squash the following: diff --git a/arch/s390/boot/physmem_info.c b/arch/s390/boot/physmem_info.c index 975fc478e0e3..6ad3ac2050eb 100644 --- a/arch/s390/boot/physmem_info.c +++ b/arch/s390/boot/physmem_info.c @@ -214,6 +214,12 @@ void detect_physmem_online_ranges(unsigned long max_physmem_end) return; } else if (physmem_info.info_source == MEM_DETECT_DIAG500_STOR_LIMIT) { max_physmem_end = 0; + /* + * If we know the storage limit but do not find any other + * indication of usable initial memory, something is messed + * up. In that case, we'll not add any physical memory so + * we'll run into die_oom() later. + */ if (!sclp_early_get_memsize(&max_physmem_end)) physmem_info.info_source = MEM_DETECT_SCLP_READ_INFO; } -- Cheers, David / dhildenb