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[2003:d8:2f37:2b00:948c:dd9f:29c8:73f4]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3d48760d1c9sm7371553f8f.17.2025.09.01.05.17.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Sep 2025 05:17:20 -0700 (PDT) Message-ID: Date: Mon, 1 Sep 2025 14:17:18 +0200 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC][PATCH v2 22/29] mm/numa: Register information into Kmemdump To: Eugen Hristev , Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, tglx@linutronix.de, andersson@kernel.org, pmladek@suse.com, linux-arm-kernel@lists.infradead.org, linux-hardening@vger.kernel.org, corbet@lwn.net, mojha@qti.qualcomm.com, rostedt@goodmis.org, jonechou@google.com, tudor.ambarus@linaro.org, Christoph Hellwig , Sergey Senozhatsky References: <20250724135512.518487-1-eugen.hristev@linaro.org> <751514db-9e03-4cf3-bd3e-124b201bdb94@redhat.com> <23e7ec80-622e-4d33-a766-312c1213e56b@redhat.com> <77d17dbf-1609-41b1-9244-488d2ce75b33@redhat.com> <9f13df6f-3b76-4d02-aa74-40b913f37a8a@redhat.com> <64a93c4a-5619-4208-9e9f-83848206d42b@linaro.org> <01c67173-818c-48cf-8515-060751074c37@linaro.org> <1b52419c-101b-487e-a961-97bd405c5c33@linaro.org> <99d2cc96-03ea-4026-883e-1ee083a96c39@redhat.com> <98afe1bd-99d2-4b5d-866a-e9541390fab4@linaro.org> <40e802eb-3764-47af-8b4f-9f7c8b5b60c1@linaro.org> <7e1f4f64-dfc4-4366-8e01-0891b2d4d2b4@redhat.com> <94f537ae-c2b1-4928-a3f3-6449c30cb624@linaro.org> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 01.09.25 14:02, Eugen Hristev wrote: > > > On 9/1/25 13:01, David Hildenbrand wrote: >>>>> What do you think ? >>>> >>>> Looks a bit over-engineered, and will require us to import a header >>>> (likely kmemdump.h) in these files, which I don't really enjoy. >>>> >>>> I would start simple, without any such macro-magic. It's a very simple >>>> function after all, and likely you won't end up having many of these? >>>> >>> >>> Thanks David, I will do it as you suggested and see what comes out of it. >>> >>> I have one side question you might know much better to answer: >>> As we have a start and a size for each region, this start is a virtual >>> address. The firmware/coprocessor that reads the memory and dumps it, >>> requires physical addresses. >> >> Right. I was asking myself the same question while reviewing: should we >> directly export physical ranges here instead of virtual ones. I guess >> virtual ones is ok. > > In patch 22/29, some areas are registered using > memblock_phys_alloc_try_nid() which allocates physical. > In this case , phys_to_virt() didn't work for me, it was returning a > wrong address. I used __va() and this worked. So there is a difference > between them. memblock_alloc_internal() calls memblock_alloc_range_nid() to then perform a phys_to_virt(). memblock_phys_alloc_try_nid() calls memblock_alloc_range_nid() without the phys_to_virt(). So it's rather surprising the a phys_to_virt() would not work in that case. Maybe for these cases where you export the area through a new helper, you can just export the physical addr + length instead. Then, it's also clear that this area is actually physically contiguous. > >> >> What do you suggest to use to retrieve that >>> address ? virt_to_phys might be problematic, __pa or __pa_symbol? or >>> better lm_alias ? >> >> All areas should either come from memblock or be global variables, right? > > I would like to be able to register from anywhere. For example someone > debugging their driver, to just register kmalloc'ed struct. > Other use case is to register dma coherent CMA areas. Then probably better to export physical addresses (that you need either way) directly from the helpers you have to add. > >> >> IIRC, virt_to_phys() should work for these. Did you run into any >> problems with them or why do you think virt_to_phys could be problematic? >> > > I am pondering about whether it would work in all cases, considering > it's source code comments that it shall not be used because it does not > work for any address. Yeah, it does for example not work for kernel stacks IIRC. -- Cheers David / dhildenb