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 06A9E1C3C11; Mon, 20 Oct 2025 18:13:06 +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=1760983987; cv=none; b=W0NKZAvxFBc9xV8gUWEtdS5CdnGidsXL2xeEMsy43Jgmurlo4FkDx5jzSbKUErnPHUrzZeknivT2JwJ/iy0Ki1BhMYzU5h5jH7xGKLPyZuMV6tAW241LerLazY4DSEM0EVrpW2oA660DqIxq3GtDBtY/6B3bYqe4H4ZPAPcGMrw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760983987; c=relaxed/simple; bh=j7luj4XAb4ynLV8eONK0lTkWrRoe+RhoyCODmNv+y1s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=s2nMWGn89uU5OkZfMYLPfNJKgOpg3uG3IkD1jE0MLe2RWvtfhafQUqleiqGKZ53d/35fyKQC2E4l0ycYf8FpEtlhM+e4vF4e0B1+WtcqbkTf6aFQliAfRZuKos1eJoSo3w91dMfKPsMzYwk33fovLTBzWDq90j/HOpQBbZEwDtQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VZtyQQ3n; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VZtyQQ3n" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2739BC4CEF9; Mon, 20 Oct 2025 18:13:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760983986; bh=j7luj4XAb4ynLV8eONK0lTkWrRoe+RhoyCODmNv+y1s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VZtyQQ3nD5oN+qtaEmIPfZybDgLjmIo0NNlWUgDn+gwy+1fGDCazcDPtuxajmmLkJ mFrSnihA0DIRn10GaytskPJlK+7+zvVcGmuHYAtAaAYUZ6tey/ddGIBFa9iy5HNjW9 8vsPUSfR6nh7clRy41g/MnzRjtRLPowuK0xwRiyBG2zVm7IYEi8/+OxbtTbmffk9QJ LLc598HBkww2ZlDBkDm0skDd6DClFK6Ojpt9ZUuPnNptCWLrQ9e4On5ab08izr5svZ 9LEHOZueUJzBtluHXKXOAm0irIbra43PmnuEurT8vYGAEFSRRthrKKb40WstS0jmod aC77Vz9N3UQSg== Date: Mon, 20 Oct 2025 21:12:57 +0300 From: Mike Rapoport To: Pasha Tatashin Cc: akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net, graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, masahiroy@kernel.org, ojeda@kernel.org, pratyush@kernel.org, rdunlap@infradead.org, tj@kernel.org, jasonmiu@google.com, dmatlack@google.com, skhawaja@google.com Subject: Re: [PATCH v6 00/10] liveupdate: Rework KHO for in-kernel users & Fix memory corruption Message-ID: References: <20251018171756.1724191-1-pasha.tatashin@soleen.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Oct 20, 2025 at 09:46:17AM -0400, Pasha Tatashin wrote: > On Mon, Oct 20, 2025 at 4:34 AM Mike Rapoport wrote: > > > > On Sat, Oct 18, 2025 at 01:17:46PM -0400, Pasha Tatashin wrote: > > > This series addresses comments and combines into one the two > > > series [1] and [2], and adds review-bys. > > > > > > This series refactors the KHO framework to better support in-kernel > > > users like the upcoming LUO. The current design, which relies on a > > > notifier chain and debugfs for control, is too restrictive for direct > > > programmatic use. > > > > > > The core of this rework is the removal of the notifier chain in favor of > > > a direct registration API. This decouples clients from the shutdown-time > > > finalization sequence, allowing them to manage their preserved state > > > more flexibly and at any time. > > > > > > Also, this series fixes a memory corruption bug in KHO that occurs when > > > KFENCE is enabled. > > > > > > The root cause is that KHO metadata, allocated via kzalloc(), can be > > > randomly serviced by kfence_alloc(). When a kernel boots via KHO, the > > > early memblock allocator is restricted to a "scratch area". This forces > > > the KFENCE pool to be allocated within this scratch area, creating a > > > conflict. If KHO metadata is subsequently placed in this pool, it gets > > > corrupted during the next kexec operation. > > > > > > [1] https://lore.kernel.org/all/20251007033100.836886-1-pasha.tatashin@soleen.com > > > [2] https://lore.kernel.org/all/20251015053121.3978358-1-pasha.tatashin@soleen.com > > > > > > Mike Rapoport (Microsoft) (1): > > > kho: drop notifiers > > > > > > Pasha Tatashin (9): > > > kho: allow to drive kho from within kernel > > > kho: make debugfs interface optional > > > kho: add interfaces to unpreserve folios and page ranes > > > kho: don't unpreserve memory during abort > > > liveupdate: kho: move to kernel/liveupdate > > > kho: move kho debugfs directory to liveupdate > > > liveupdate: kho: warn and fail on metadata or preserved memory in scratch area > > > liveupdate: kho: Increase metadata bitmap size to PAGE_SIZE > > > liveupdate: kho: allocate metadata directly from the buddy allocator > > > > The fixes should go before the preparation for LUO or even better as a > > separate series. > > > > I've reread the LUO preparation patches and I don't think they are useful > > on their own. They introduce a couple of unused interfaces and I think it's > > better to have them along with the rest of LUO patches. > > Pulling them out to apply fixes separately feels counterproductive, > especially since we agreed to add the new kexec_handover_debug.c file. > The most straightforward path is to build on what's already in -next. > Let's stick with the current approach. The fixes are 6.18 material, the LUO preparation is 6.19 material. > Thanks, > Pasha > > > > > -- > > Sincerely yours, > > Mike. -- Sincerely yours, Mike.