[Bug 1970672] Re: makedumpfile falls back to cp with "__vtop4_x86_64: Can't get a valid pmd_pte."
Dimitri John Ledkov
1970672 at bugs.launchpad.net
Wed Nov 22 01:35:04 UTC 2023
$ dput ubuntu makedumpfile_1.6.7-1ubuntu2.5_source.changes
D: Setting host argument.
Checking signature on .changes
gpg: /tmp/makedumpfile_1.6.7-1ubuntu2.5_source.changes: Valid signature from 9B8EC849D5EF70ED
Checking signature on .dsc
gpg: /tmp/makedumpfile_1.6.7-1ubuntu2.5.dsc: Valid signature from 9B8EC849D5EF70ED
Uploading to ubuntu (via ftp to upload.ubuntu.com):
Uploading makedumpfile_1.6.7-1ubuntu2.5.dsc: done.
Uploading makedumpfile_1.6.7-1ubuntu2.5.debian.tar.xz: done.
Uploading makedumpfile_1.6.7-1ubuntu2.5_source.buildinfo: done.
Uploading makedumpfile_1.6.7-1ubuntu2.5_source.changes: done.
Successfully uploaded packages.
** Changed in: makedumpfile (Ubuntu)
Status: Confirmed => Fix Released
** Changed in: makedumpfile (Ubuntu Focal)
Status: Confirmed => In Progress
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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:
Fix Released
Status in makedumpfile source package in Focal:
In Progress
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 <k-hagio-ab at nec.com>
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 <k-hagio-ab at nec.com>
[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.
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