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 35762302CDC; Fri, 28 Nov 2025 09:30:21 +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=1764322222; cv=none; b=SS5Yh+3VpU3BYDyDnj6saVW+EKlkVSo9o28RnWeFZWD9kBhbW/1gWpvV1m2J9oauQriLW1YqB+6nPlj2lPQH6BAtDLM4qGsrZ9CJ5I1PrZRpz1NuMPwbVmCyW2d5Ek7oy7dmDjz97EloVLITsfuF4dJKNJw3Qv19FwtMXK19Vk4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764322222; c=relaxed/simple; bh=c+ju217X/Iu2Eyrw3ITJ5fQi1c/hHwxKC7muOjOFeAM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RWjarYT8FAXTnuS1lqD1Vr2pUtDRCZdpSk43kR+8CcEYwUOCH9L2HdMQ/FQW07+wqLnHciKh833TjW5ZQRYR9wp7cZlv4CCML0Qzcf8rOWkxWAgnl7fYvORZz1bQPyeslfUuuu6CFn6QWHJQqtiYqSg8Ca5eG25LBKcSYZTNhkA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qd2NiCXu; 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="qd2NiCXu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19BA9C2BCB8; Fri, 28 Nov 2025 09:30:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764322221; bh=c+ju217X/Iu2Eyrw3ITJ5fQi1c/hHwxKC7muOjOFeAM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=qd2NiCXui9tsiwdCYok4UcUDQqTMMHZ6dOVLI2a8Xq54o7qj/gy6iWGAmfeyWL5FA AsOozZOa2wastuPtMQVwdg+nw8TUIggbbXDbFvAXxxuRXII5OylWbCEY0d0IK7wAWz YWD+EnnPEc5wBSsoeAdM35iCQM2bQmQXYCl83xolfiOZLxpllI6bTnSbqXqKeSPA6y JNgKKja898564OBPnGHhqQ5sySb/JvG6rdgJsmNB+YH5OWCZYPmzzCKCsmOfzJvWh4 UO4uKNdhhtpsauOOAJQyf34Zczo24r/NZ29e9HNiu1foo4xfKEQQKStJKSQcPQGtua Yv3nsgTV78cFQ== Message-ID: Date: Fri, 28 Nov 2025 10:30:15 +0100 Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/4] mm: Add support for unaccepted memory hotplug To: Borislav Petkov , Kiryl Shutsemau Cc: "Pratik R. Sampat" , linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, ardb@kernel.org, akpm@linux-foundation.org, osalvador@suse.de, thomas.lendacky@amd.com, michael.roth@amd.com References: <20251125175753.1428857-1-prsampat@amd.com> <20251125175753.1428857-3-prsampat@amd.com> <66ylzwknm4ftd6utn3nqr63jmhl2ccvcdvyi5fechfnvmfxivu@37pckhjixayh> <20251126223127.GIaSd_v7juUkaW4RTA@fat_crate.local> <20251127181233.GBaSiUkaLzwANS_6WT@fat_crate.local> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <20251127181233.GBaSiUkaLzwANS_6WT@fat_crate.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/27/25 19:12, Borislav Petkov wrote: > On Thu, Nov 27, 2025 at 05:35:57PM +0000, Kiryl Shutsemau wrote: >>> ABI break for kexec? Is that a thing? >>> >>> Since when do we enforce ABI compatibility for kexec and where are we >>> documenting that? > > I'll take that as a "no". > >> The whole purpose of kexec() is to switch between kernel versions. This >> struct defines format we communicate information about unaccepted memory >> between kernels. The mismatch will lead to boot failure. >> >> The structure is versioned. Ideally, we should know the format of the >> structure the next kernel supports and act accordingly in the first >> kernel. Like, we can accept all memory before kexec on mismatch. > > None of that matters if you kexec the same kernels. > > IOW, for some reason you want to be able to kexec different kernels. The > question is why do we care? kexecing the same kernel is typically used for kdump purposes. kexecing different kernels is used for all sorts of things (live-upgrade, grub-emu come to mind). It's quite common to kexec different kernels, or maybe I misunderstood the question here? -- Cheers David