* Re: [PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT [not found] ` <655c509e-318f-48bc-8183-2b1274dd05ac@kernel.org> @ 2026-09-28 8:01 ` Dave Young 2026-09-28 8:50 ` David Hildenbrand (Arm) 0 siblings, 1 reply; 2+ messages in thread From: Dave Young @ 2026-09-28 8:01 UTC (permalink / raw) To: David Hildenbrand (Arm) Cc: David Carlier, akpm, axelrasmussen, baohua, baolin.wang, baoquan.he, brendan.jackman, dakr, driver-core, gregkh, hannes, jan.kiszka, kasong, kbingham, liam, linux-cxl, linux-fsdevel, linux-kernel, linux-mm, ljs, mhocko, osalvador, qi.zheng, rafael, rppt, shakeel.butt, surenb, vbabka, weixugc, yuanchu, ziy, devel, kexec Cced kexec list. On Mon, Sep 28, 2026 at 09:28:08AM +0200, David Hildenbrand (Arm) wrote: > On 9/27/26 21:20, David Carlier wrote: > > On Mon, Sep 21, 2026 at 09:59:02PM +0200, David Hildenbrand (Arm) wrote: > >> enum { > >> - SECTION_MARKED_PRESENT_BIT, > >> SECTION_HAS_MEM_MAP_BIT, > >> SECTION_IS_ONLINE_BIT, > >> SECTION_IS_EARLY_BIT, > > > > Hi David, > > Hi! > > > > > It seems dropping SECTION_MARKED_PRESENT_BIT shifts the other section flags down > > one bit. crash hardcodes SECTION_HAS_MEM_MAP as (1UL << 1) in > > pfn_to_map(), so it now tests SECTION_IS_ONLINE: offline and > > ZONE_DEVICE sections no longer resolve to a struct page. makedumpfile > > only checks bit 0 and is fine. > > Thanks. To be expected when relying on kernel internals. > > Which makes me wonder why makedumpfile > (https://github.com/makedumpfile/makedumpfile) not require any such information. > > > > > Keep bit 0 reserved, or export the bits via vmcoreinfo? > We could export it, or crash can simply detect the change based on the kernel > version. I remember the latter was done in makedumpfile in the past (although we > export it). > > I can send a separate patch to export it. Thanks David. Checking kernel internals via kernel version is not a good idea due to the downstream kernels. > > -- > Cheers, > > David ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT 2026-09-28 8:01 ` [PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT Dave Young @ 2026-09-28 8:50 ` David Hildenbrand (Arm) 0 siblings, 0 replies; 2+ messages in thread From: David Hildenbrand (Arm) @ 2026-09-28 8:50 UTC (permalink / raw) To: Dave Young Cc: David Carlier, akpm, axelrasmussen, baohua, baolin.wang, baoquan.he, brendan.jackman, dakr, driver-core, gregkh, hannes, jan.kiszka, kasong, kbingham, liam, linux-cxl, linux-fsdevel, linux-kernel, linux-mm, ljs, mhocko, osalvador, qi.zheng, rafael, rppt, shakeel.butt, surenb, vbabka, weixugc, yuanchu, ziy, devel, kexec, Baoquan He On 9/28/26 10:01, Dave Young wrote: > Cced kexec list. > > On Mon, Sep 28, 2026 at 09:28:08AM +0200, David Hildenbrand (Arm) wrote: >> On 9/27/26 21:20, David Carlier wrote: >>> >>> Hi David, >> >> Hi! >> >>> >>> It seems dropping SECTION_MARKED_PRESENT_BIT shifts the other section flags down >>> one bit. crash hardcodes SECTION_HAS_MEM_MAP as (1UL << 1) in >>> pfn_to_map(), so it now tests SECTION_IS_ONLINE: offline and >>> ZONE_DEVICE sections no longer resolve to a struct page. makedumpfile >>> only checks bit 0 and is fine. >> >> Thanks. To be expected when relying on kernel internals. >> >> Which makes me wonder why makedumpfile >> (https://github.com/makedumpfile/makedumpfile) not require any such information. >> >>> >>> Keep bit 0 reserved, or export the bits via vmcoreinfo? >> We could export it, or crash can simply detect the change based on the kernel >> version. I remember the latter was done in makedumpfile in the past (although we >> export it). >> >> I can send a separate patch to export it. > > Thanks David. Checking kernel internals via kernel version is not a good idea > due to the downstream kernels. Patch at: https://lore.kernel.org/r/20260928-section_has_mem_map-v1-1-4129f6ba2838@kernel.org -- Cheers, David ^ permalink raw reply [flat|nested] 2+ messages in thread
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[not found] ` <655c509e-318f-48bc-8183-2b1274dd05ac@kernel.org>
2026-09-28 8:01 ` [PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT Dave Young
2026-09-28 8:50 ` David Hildenbrand (Arm)
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