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(p200300cbc7337c00d067e3274f997546.dip0.t-ipconnect.de. [2003:cb:c733:7c00:d067:e327:4f99:7546]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38058b49d20sm14784530f8f.62.2024.10.30.02.42.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 30 Oct 2024 02:42:07 -0700 (PDT) Message-ID: <35fc960b-0013-4264-93d6-6511d54ab474@redhat.com> Date: Wed, 30 Oct 2024 10:42:05 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/7] s390/physmem_info: query diag500(STORAGE LIMIT) to support QEMU/KVM memory devices To: Heiko Carstens 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, Vasily Gorbik , Alexander Gordeev , 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?= , Eric Farman , Andrew Morton , Jonathan Corbet , Mario Casquero References: <20241025141453.1210600-1-david@redhat.com> <20241025141453.1210600-4-david@redhat.com> <20241030092324.6264-E-hca@linux.ibm.com> From: David Hildenbrand 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: <20241030092324.6264-E-hca@linux.ibm.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-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 2479F80003 X-Stat-Signature: 6ftrjdia1bcqqp5eb95krw4r84kroha9 X-Rspam-User: X-HE-Tag: 1730281282-479422 X-HE-Meta: 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 QOQ8n4vf akK3Uu+jB+oOj2Zj69Kc35DW99LnPduBNfs/oH9TPDwasDnBdmDxVwvXUVNpdEoosXwmwQPwVsB0uPiBl87oT+xJmWRUlf5NAfzb1BBT7zFsAdHy4klyXxmCTItIx1JbdeXKlCBlr8brw3sEv7kLHNI87yD7h99vv/k2yLO36S4wAklQuCVX1qdiQ3rj5KFHDZWp35l0R8gi7mOmOVLpooTPOHsBBJLl/jFp+IpdKvlxTsFSVlgQXpXqF4OOLTQClqJ23bihVtPRYLkhCkRj+FMuyp+bx+D8G1O1xdvS3WN6PUM9/R46vfKPnfhikFGcL08YwisxPY9FCkqBrjwHsSPKCxo8WBS3PkGojkdMUWUYhsJnMynrMRqbIsVOogUNZy9QadxCaguIyN16yxMf+917HwEA26Hd0q19j2UqlK29ejMYk2I6DTc8UOHlnINVCVHgAlMY9MfxC4e0nMUzSkDLQXw== 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 30.10.24 10:23, Heiko Carstens wrote: > On Fri, Oct 25, 2024 at 04:14:48PM +0200, David Hildenbrand wrote: >> To support memory devices under QEMU/KVM, such as virtio-mem, >> we have to prepare our kernel virtual address space accordingly and >> have to know the highest possible physical memory address we might see >> later: the storage limit. The good old SCLP interface is not suitable for >> this use case. >> >> In particular, memory owned by memory devices has no relationship to >> storage increments, it is always detected using the device driver, and >> unaware OSes (no driver) must never try making use of that memory. >> Consequently this memory is located outside of the "maximum storage >> increment"-indicated memory range. >> >> Let's use our new diag500 STORAGE_LIMIT subcode to query this storage >> limit that can exceed the "maximum storage increment", and use the >> existing interfaces (i.e., SCLP) to obtain information about the initial >> memory that is not owned+managed by memory devices. >> >> If a hypervisor does not support such memory devices, the address exposed >> through diag500 STORAGE_LIMIT will correspond to the maximum storage >> increment exposed through SCLP. >> >> To teach kdump on s390 to include memory owned by memory devices, there >> will be ways to query the relevant memory ranges from the device via a >> driver running in special kdump mode (like virtio-mem already implements >> to filter /proc/vmcore access so we don't end up reading from unplugged >> device blocks). >> >> Update setup_ident_map_size(), to clarify that there can be more than >> just online and standby memory. >> >> Tested-by: Mario Casquero >> Signed-off-by: David Hildenbrand >> --- >> arch/s390/boot/physmem_info.c | 47 +++++++++++++++++++++++++++- >> arch/s390/boot/startup.c | 7 +++-- >> arch/s390/include/asm/physmem_info.h | 3 ++ >> 3 files changed, 54 insertions(+), 3 deletions(-) > > Looks like I couldn't convince you to implement a query subcode. Well, you convinced me that it might be useful, but after waiting on feedback from the KVM folks ... which didn't happen I moved on. In the cover letter I have "No query function for diag500 for now." My thinking was that if we go for a query subcode, maybe we'd start "anew" with a new diag and use "0=query" like all similar instructions I am aware of. And that is then a bigger rework ... ... and I am not particularly interested in extra work without a clear statement from KVM people what (a) if that work is required and; (b) what it should look like. Thanks for the review Heiko! -- Cheers, David / dhildenb