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 B76DEF9FE; Sun, 9 Feb 2025 15:10:49 +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=1739113849; cv=none; b=aphbc4aDw8j35MLvfryUT4e3cHCVlm4EbEIWYLDm69J3GYY4JKX9C743faxl2AmLRluw5pSc/Ph/PBWb7+dN3n70+gyDVNzudii5udcRNh1njfqaD6pAqFA8dwQ09dkxhxreXzzIqo9Hr3avT3wG0hgfdKtO0USf0HPjRcib6D4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739113849; c=relaxed/simple; bh=J7RPEEvR3YN2Zw3FJPrsXlkP5CHQ4ry6huE55PuC5gQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GfGVWUu0yBaxpMFGvvyAAjaKdsertJwUnl9eyUoZ+d6cH7PZmea7GqIwAXcvlOETbGEjp9JEAGXYAfpXKoEKyQPneBT5R4sHAUSjT6BuyuriGOJhiIfZSDom7mMvLiIL2m/aEfc6YQ2Y5Ytxy0X6TZA1q2HSIyhHe13yk4VPfBs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=vRjbl4gP; 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="vRjbl4gP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5A64C4CEE2; Sun, 9 Feb 2025 15:10:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739113849; bh=J7RPEEvR3YN2Zw3FJPrsXlkP5CHQ4ry6huE55PuC5gQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vRjbl4gPV6wrAL1Op6b4UG/ZsW9dGApg6AGSIrvaNSkhp6cSEu2/MeZlFcqZZwjMp VGmvNeICYY50N390bDunkJ9Pxo8RsJ0xTNfcJ1laLEVHM/S3P4HVCK7Ylo35ky9VjV O3IQhIQFVExy2+rPS31ctiOp4I+goc35/Loe/O/4jtbq+ywEvbpBhgIMSbwVd3fu8Q 0f37CHSCjlpBrAGCyeVigrg+mNP3UavBOj7iXkp6DeeSFvXuwwlhF4XECVIDSp98q8 /uFv9cqyP3oCkixs4eyYjxu9KhtbCiIeLV+7GxHChQk+OC0ltm6uGrYLdetui3ZO6D h8fHOZbzeBvEw== Date: Sun, 9 Feb 2025 17:10:28 +0200 From: Mike Rapoport To: Krzysztof Kozlowski Cc: linux-kernel@vger.kernel.org, Alexander Graf , Andrew Morton , Andy Lutomirski , Anthony Yznaga , Arnd Bergmann , Ashish Kalra , Benjamin Herrenschmidt , Borislav Petkov , Catalin Marinas , Dave Hansen , David Woodhouse , Eric Biederman , Ingo Molnar , James Gowans , Jonathan Corbet , Mark Rutland , Paolo Bonzini , Pasha Tatashin , "H. Peter Anvin" , Peter Zijlstra , Pratyush Yadav , Rob Herring , Rob Herring , Saravana Kannan , Stanislav Kinsburskii , Steven Rostedt , Thomas Gleixner , Tom Lendacky , Usama Arif , Will Deacon , devicetree@vger.kernel.org, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Subject: Re: [PATCH v4 14/14] Documentation: KHO: Add memblock bindings Message-ID: References: <20250206132754.2596694-1-rppt@kernel.org> <20250206132754.2596694-15-rppt@kernel.org> <45df0d7a-622a-4268-9683-c5c6067483c3@kernel.org> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45df0d7a-622a-4268-9683-c5c6067483c3@kernel.org> On Sun, Feb 09, 2025 at 11:29:41AM +0100, Krzysztof Kozlowski wrote: > On 06/02/2025 14:27, Mike Rapoport wrote: > > From: "Mike Rapoport (Microsoft)" > > > > We introduced KHO into Linux: A framework that allows Linux to pass > > metadata and memory across kexec from Linux to Linux. KHO reuses fdt > > as file format and shares a lot of the same properties of firmware-to- > > Linux boot formats: It needs a stable, documented ABI that allows for > > forward and backward compatibility as well as versioning. > > Please use subject prefixes matching the subsystem. You can get them for > example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory > your patch is touching. For bindings, the preferred subjects are > explained here: > https://www.kernel.org/doc/html/latest/devicetree/bindings/submitting-patches.html#i-for-patch-submitters These are not devicetree binding for communicating data from firmware to the kernel. These bindings are specific to KHO which is perfectly reflected by the subject. Just a brief reminder from v2 discussion: (https://lore.kernel.org/linux-mm/20231222193607.15474-1-graf@amazon.com/) "For quick reference: KHO is a new mechanism this patch set introduces which allows Linux to pass arbitrary memory and metadata between kernels on kexec. I'm reusing FDTs to implement the hand over protocol, as Linux-to-Linux boot communication holds very similar properties to firmware-to-Linux boot communication. So this binding is not about hardware; it's about preserving Linux subsystem state across kexec. For more details, please refer to the KHO documentation which is part of patch 7 of this patch set: https://lore.kernel.org/lkml/20231222195144.24532-2-graf@amazon.com/" and "This is our own data structure for KHO that just happens to again contain a DT structure. The reason is simple: I want a unified, versioned, introspectable data format that is cross platform so you don't need to touch every architecture specific boot passing logic every time you want to add a tiny piece of data." > > As first user of KHO, we introduced memblock which can now preserve > > memory ranges reserved with reserve_mem command line options contents > > across kexec, so you can use the post-kexec kernel to read traces from > > the pre-kexec kernel. > > > > This patch adds memblock schemas similar to "device" device tree ones to > > a new kho bindings directory. This allows us to force contributors to > > document the data that moves across KHO kexecs and catch breaking change > > during review. > > > > Co-developed-by: Alexander Graf > > Signed-off-by: Alexander Graf > > Signed-off-by: Mike Rapoport (Microsoft) > > --- > > .../kho/bindings/memblock/reserve_mem.yaml | 41 ++++++++++++++++++ > > .../bindings/memblock/reserve_mem_map.yaml | 42 +++++++++++++++++++ > > 2 files changed, 83 insertions(+) > > create mode 100644 Documentation/kho/bindings/memblock/reserve_mem.yaml > > create mode 100644 Documentation/kho/bindings/memblock/reserve_mem_map.yaml > > > > diff --git a/Documentation/kho/bindings/memblock/reserve_mem.yaml b/Documentation/kho/bindings/memblock/reserve_mem.yaml > > new file mode 100644 > > index 000000000000..7b01791b10b3 > > --- /dev/null > > +++ b/Documentation/kho/bindings/memblock/reserve_mem.yaml > > @@ -0,0 +1,41 @@ > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > > +%YAML 1.2 > > +--- > > +$id: http://devicetree.org/schemas/memblock/reserve_mem.yaml# > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > + > > +title: Memblock reserved memory > > + > > +maintainers: > > + - Mike Rapoport > > + > > +description: | > > + Memblock can serialize its current memory reservations created with > > + reserve_mem command line option across kexec through KHO. > > + The post-KHO kernel can then consume these reservations and they are > > + guaranteed to have the same physical address. > > + > > +examples: > > + - | > > + reserve_mem { > > Again, do not introduce own coding style. > > I don't understand why do you need this in the first place. There is > already reserved-memory block. Because these regions are not "... designed for the special usage by various device drivers" and should not be exclude by the operating system from normal usage. > Best regards, > Krzysztof -- Sincerely yours, Mike.