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(p200300cbc7054200ce79acf6d83260df.dip0.t-ipconnect.de. [2003:cb:c705:4200:ce79:acf6:d832:60df]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-433b45fa728sm14606045e9.14.2024.11.20.02.48.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Nov 2024 02:48:44 -0800 (PST) Message-ID: <4b07a3eb-aad6-4436-9591-289c6504bb92@redhat.com> Date: Wed, 20 Nov 2024 11:48:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 07/11] fs/proc/vmcore: introduce PROC_VMCORE_DEVICE_RAM to detect device RAM ranges in 2nd kernel To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, virtualization@lists.linux.dev, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, kexec@lists.infradead.org, Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Vivek Goyal , Dave Young , Thomas Huth , Cornelia Huck , Janosch Frank , Claudio Imbrenda , Eric Farman , Andrew Morton References: <20241025151134.1275575-1-david@redhat.com> <20241025151134.1275575-8-david@redhat.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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: WiVYG8QkPpTxS_jY3I9JN07t95YRLWxFL6YwCpU-TM4_1732099726 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4473EC0007 X-Stat-Signature: rqsjdk9wc3z8zhnt5o8ocxqjgijxa8r1 X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1732099706-337042 X-HE-Meta: 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 ttQu7+hN 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 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 20.11.24 11:13, Baoquan He wrote: > On 10/25/24 at 05:11pm, David Hildenbrand wrote: >> s390 allocates+prepares the elfcore hdr in the dump (2nd) kernel, not in >> the crashed kernel. >> >> RAM provided by memory devices such as virtio-mem can only be detected >> using the device driver; when vmcore_init() is called, these device >> drivers are usually not loaded yet, or the devices did not get probed >> yet. Consequently, on s390 these RAM ranges will not be included in >> the crash dump, which makes the dump partially corrupt and is >> unfortunate. >> >> Instead of deferring the vmcore_init() call, to an (unclear?) later point, >> let's reuse the vmcore_cb infrastructure to obtain device RAM ranges as >> the device drivers probe the device and get access to this information. >> >> Then, we'll add these ranges to the vmcore, adding more PT_LOAD >> entries and updating the offsets+vmcore size. >> >> Use Kconfig tricks to include this code automatically only if (a) there is >> a device driver compiled that implements the callback >> (PROVIDE_PROC_VMCORE_DEVICE_RAM) and; (b) the architecture actually needs >> this information (NEED_PROC_VMCORE_DEVICE_RAM). >> >> The current target use case is s390, which only creates an elf64 >> elfcore, so focusing on elf64 is sufficient. >> >> Signed-off-by: David Hildenbrand >> --- >> fs/proc/Kconfig | 25 ++++++ >> fs/proc/vmcore.c | 156 +++++++++++++++++++++++++++++++++++++ >> include/linux/crash_dump.h | 9 +++ >> 3 files changed, 190 insertions(+) >> >> diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig >> index d80a1431ef7b..1e11de5f9380 100644 >> --- a/fs/proc/Kconfig >> +++ b/fs/proc/Kconfig >> @@ -61,6 +61,31 @@ config PROC_VMCORE_DEVICE_DUMP >> as ELF notes to /proc/vmcore. You can still disable device >> dump using the kernel command line option 'novmcoredd'. >> >> +config PROVIDE_PROC_VMCORE_DEVICE_RAM >> + def_bool n >> + >> +config NEED_PROC_VMCORE_DEVICE_RAM >> + def_bool n >> + >> +config PROC_VMCORE_DEVICE_RAM >> + def_bool y >> + depends on PROC_VMCORE >> + depends on NEED_PROC_VMCORE_DEVICE_RAM >> + depends on PROVIDE_PROC_VMCORE_DEVICE_RAM > > Kconfig item is always a thing I need learn to master. Yes, it's usually a struggle to get it right. It took me a couple of iterations to get to this point :) > When I checked > this part, I have to write them down to deliberate. I am wondering if > below 'simple version' works too and more understandable. Please help > point out what I have missed. > > ===========simple version====== > config PROC_VMCORE_DEVICE_RAM > def_bool y > depends on PROC_VMCORE && VIRTIO_MEM > depends on NEED_PROC_VMCORE_DEVICE_RAM > > config S390 > select NEED_PROC_VMCORE_DEVICE_RAM > ============ So the three changes you did are (a) Remove the config option but select/depend on them. (b) Remove the "depends on PROC_VMCORE" from PROC_VMCORE_DEVICE_RAM, and the "if PROC_VMCORE" from s390. (c) Remove the PROVIDE_PROC_VMCORE_DEVICE_RAM Regarding (a), that doesn't work. If you select a config option that doesn't exist, it is silently dropped. It's always treated as if it wouldn't be set. Regarding (b), I think that's an anti-pattern (having config options enabled that are completely ineffective) and I don't see a benefit dropping them. Regarding (c), it would mean that s390x unconditionally includes that code even if virtio-mem is not configured in. So while we could drop PROVIDE_PROC_VMCORE_DEVICE_RAM -- (c), it would that we end up including code in configurations that don't possibly need it. That's why I included that part. > > > ======= config items extracted from this patchset==== > config PROVIDE_PROC_VMCORE_DEVICE_RAM > def_bool n > > config NEED_PROC_VMCORE_DEVICE_RAM > def_bool n > > config PROC_VMCORE_DEVICE_RAM > def_bool y > depends on PROC_VMCORE > depends on NEED_PROC_VMCORE_DEVICE_RAM > depends on PROVIDE_PROC_VMCORE_DEVICE_RAM > > config VIRTIO_MEM > depends on X86_64 || ARM64 || RISCV > ~~~~~ I don't get why VIRTIO_MEM dones't depend on S390 if > s390 need PROC_VMCORE_DEVICE_RAM. This series depends on s390 support for virtio-mem, which just went upstream. See commit 38968bcdcc1d46f2fdcd3a72599d5193bf8baf84 Author: David Hildenbrand Date: Fri Oct 25 16:14:49 2024 +0200 virtio-mem: s390 support > ...... > select PROVIDE_PROC_VMCORE_DEVICE_RAM if PROC_VMCORE > > config S390 > select NEED_PROC_VMCORE_DEVICE_RAM if PROC_VMCORE > ================================================= > Thanks for having a look! -- Cheers, David / dhildenb