From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 91A333783C8 for ; Mon, 23 Mar 2026 22:00:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774303202; cv=none; b=hqMrclzZ/NiV8vRRE9E43n6MCuJvuMYCaVnyVMk+B6dfVqantzW3z/4HS9+guhAmka+vflMFE8tivzh25QEkoUAlUMCSc4CEZKpoXqv4YV0RP6eSuqTBiPggebIuv3nq15fuJaz8Vw4KWsKV/PM8s7WVTC/kGBa/oIAuDQ58ryM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774303202; c=relaxed/simple; bh=n6EBJY1LOSTGKkF/EeGoMzinOvjJ51/Rr3weer2gCRs=; h=Date:To:From:Subject:Message-Id; b=Cx2EWmg5vW3xAMY/drHRO4NjNZQkn84cCDuUlhM7AwUzs44o2qk+XZVa5zqUHayvnFl8XF/BGVy2QHWPZX8LrZAGOnc+gYTPV2fFj3hfTD4MxiXeBVGBG65s31FpgWkQ/zIoil5jYiKQn1q28GGeD9m/pH33EMA9cA+FmOxbjEk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=vrlzmDLA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="vrlzmDLA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAE43C4CEF7; Mon, 23 Mar 2026 22:00:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1774303202; bh=n6EBJY1LOSTGKkF/EeGoMzinOvjJ51/Rr3weer2gCRs=; h=Date:To:From:Subject:From; b=vrlzmDLAyb0VL+uloor2cqJY/xp4LlyvdNTlgYO8vr4MQ9BMtuBySyzifsM6JSN5r WeA6HCe8+p0bR3pleuJWojm2nKUPYYeakiVeZs1B0M8V/qgZExnGkE3W4gf2v8QkJw QFDdEll8RnCUA8XmIeoyVEUs0c3iVYLZeY2Wncgc= Date: Mon, 23 Mar 2026 15:00:01 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,surenb@google.com,skhan@linuxfoundation.org,sj@kernel.org,rppt@kernel.org,pratyush@kernel.org,pasha.tatashin@soleen.com,mhocko@suse.com,ljs@kernel.org,Liam.Howlett@oracle.com,graf@amazon.com,david@kernel.org,corbet@lwn.net,leitao@debian.org,akpm@linux-foundation.org From: Andrew Morton Subject: + kho-document-kexec-metadata-tracking-feature.patch added to mm-nonmm-unstable branch Message-Id: <20260323220001.EAE43C4CEF7@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: kho: document kexec-metadata tracking feature has been added to the -mm mm-nonmm-unstable branch. Its filename is kho-document-kexec-metadata-tracking-feature.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kho-document-kexec-metadata-tracking-feature.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Breno Leitao Subject: kho: document kexec-metadata tracking feature Date: Mon, 16 Mar 2026 04:54:36 -0700 Add documentation for the kexec-metadata feature that tracks the previous kernel version and kexec boot count across kexec reboots. This helps diagnose bugs that only reproduce when kexecing from specific kernel versions. Link: https://lkml.kernel.org/r/20260316-kho-v9-6-ed6dcd951988@debian.org Signed-off-by: Breno Leitao Suggested-by: Mike Rapoport Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Pratyush Yadav Cc: Alexander Graf Cc: David Hildenbrand Cc: Jonathan Corbet Cc: "Liam R. Howlett" Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Pasha Tatashin Cc: SeongJae Park Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- Documentation/admin-guide/mm/kho.rst | 39 +++++++++++++++++++++++++ 1 file changed, 39 insertions(+) --- a/Documentation/admin-guide/mm/kho.rst~kho-document-kexec-metadata-tracking-feature +++ a/Documentation/admin-guide/mm/kho.rst @@ -42,6 +42,45 @@ For example, if you used ``reserve_mem`` an early memory reservation, the new kernel will have that memory at the same physical address as the old kernel. +Kexec Metadata +============== + +KHO automatically tracks metadata about the kexec chain, passing information +about the previous kernel to the next kernel. This feature helps diagnose +bugs that only reproduce when kexecing from specific kernel versions. + +On each KHO kexec, the kernel logs the previous kernel's version and the +number of kexec reboots since the last cold boot:: + + [ 0.000000] KHO: exec from: 6.19.0-rc4-next-20260107 (count 1) + +The metadata includes: + +``previous_release`` + The kernel version string (from ``uname -r``) of the kernel that + initiated the kexec. + +``kexec_count`` + The number of kexec boots since the last cold boot. On cold boot, + this counter starts at 0 and increments with each kexec. This helps + identify issues that only manifest after multiple consecutive kexec + reboots. + +Use Cases +--------- + +This metadata is particularly useful for debugging kexec transition bugs, +where a buggy kernel kexecs into a new kernel and the bug manifests only +in the second kernel. Examples of such bugs include: + +- Memory corruption from the previous kernel affecting the new kernel +- Incorrect hardware state left by the previous kernel +- Firmware/ACPI state issues that only appear in kexec scenarios + +At scale, correlating crashes to the previous kernel version enables +faster root cause analysis when issues only occur in specific kernel +transition scenarios. + debugfs Interfaces ================== _ Patches currently in -mm which might be from leitao@debian.org are mm-khugepaged-export-set_recommended_min_free_kbytes.patch mm-huge_memory-refactor-anon_enabled_store-with-set_anon_enabled_mode.patch mm-huge_memory-refactor-enabled_store-with-set_global_enabled_mode.patch mm-ratelimit-min_free_kbytes-adjustment-messages.patch mm-kmemleak-add-config_debug_kmemleak_verbose-build-option.patch kho-add-size-parameter-to-kho_add_subtree.patch kho-rename-fdt-parameter-to-blob-in-kho_add-remove_subtree.patch kho-persist-blob-size-in-kho-fdt.patch kho-fix-kho_in_debugfs_init-to-handle-non-fdt-blobs.patch kho-kexec-metadata-track-previous-kernel-chain.patch kho-document-kexec-metadata-tracking-feature.patch