Thanks Kellen and Cascardo. Kellen, nice that you're willing to work on that - this is a long standing problem and that work would be definitely appreciated by the Ubuntu community, be it free users or the Ubuntu Advantage customers!
Cascardo, about your two risks: (a) Partially agree with that. I agree with the part of testing, definietly this is the big chunk of work here. But I disagree with the retrocompatibility claim: of course we need to enforce that, but it's not that difficult in the LTS->LTS+1 model. See, we have a small number of HWE kernel per LTS release, I guess 4 or 5 correct? We need to be sure the makedumpfile updates are compatible with them, and that's it. If I'm talking Focal and some makedumpfile update (unintentionally) breaks dumps for kernel 4.19 or prior, why should we care if that's an unsupported scenario? IMHO it's much better to ensure that every HWE kernel receives a proper functional makedumpfile update, instead of an overly cautious attitude with older/unsupported kernels. (b) I agree here, but I guess the effort of SRU exception/ LTS->LTS+1 model will only make it easier. Imagine if when Ubuntu version X is released the upstream makedumpfile is not handling well the recent kernel version used by X - so we could either fix (or report) the makedumpfile issue quickly (especially due to part (a) above, the improved testing). Then, once it's fixed either by Canonical or community, this could quickly be integrated through a fast process, a version bump for makedumpfile for example. In the end, I think testing is the key word here - the more serious and thorough tests makedumpfile has, the more confidence in such model we'd have. But hopefully with Kellen's effort this stops preventing a more proactive approach with makedumpfile from happening, by updating it before users report bugs (which has been happening since forever for this package). Cheers! -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to makedumpfile in Ubuntu. https://bugs.launchpad.net/bugs/1970672 Title: makedumpfile falls back to cp with "__vtop4_x86_64: Can't get a valid pmd_pte." Status in makedumpfile package in Ubuntu: New Bug description: [Impact] * On Focal with an HWE (>=5.12) kernel, makedumpfile can sometimes fail with "__vtop4_x86_64: Can't get a valid pmd_pte." * makedumpfile falls back to cp for the dump, resulting in extremely large vmcores. This can impact both collection and analysis due to lack of space for the resulting vmcore. * This is fixed in upstream commit present in versions 1.7.0 and 1.7.1: https://github.com/makedumpfile/makedumpfile/commit/646456862df8926ba10dd7330abf3bf0f887e1b6 commit 646456862df8926ba10dd7330abf3bf0f887e1b6 Author: Kazuhito Hagio <[email protected]> Date: Wed May 26 14:31:26 2021 +0900 [PATCH] Increase SECTION_MAP_LAST_BIT to 5 * Required for kernel 5.12 Kernel commit 1f90a3477df3 ("mm: teach pfn_to_online_page() about ZONE_DEVICE section collisions") added a section flag (SECTION_TAINT_ZONE_DEVICE) and causes makedumpfile an error on some machines like this: __vtop4_x86_64: Can't get a valid pmd_pte. readmem: Can't convert a virtual address(ffffe2bdc2000000) to physical address. readmem: type_addr: 0, addr:ffffe2bdc2000000, size:32768 __exclude_unnecessary_pages: Can't read the buffer of struct page. create_2nd_bitmap: Can't exclude unnecessary pages. Increase SECTION_MAP_LAST_BIT to 5 to fix this. The bit had not been used until the change, so we can just increase the value. Signed-off-by: Kazuhito Hagio <[email protected]> [Test Plan] * Confirm that makedumpfile works as expected by triggering a kdump. * Confirm that the patched makedumpfile works as expected on a system known to experience the issue. * Confirm that the patched makedumpfile is able to work with a cp- generated known affected vmcore to compress it. The unpatched version fails. [Where problems could occur] * This change could adversely affect the collection/compression of vmcores during a kdump situation resulting in fallback to cp. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/makedumpfile/+bug/1970672/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
