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 CFAA52D838A; Wed, 20 Aug 2025 08:20:50 +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=1755678050; cv=none; b=U5m2kRtXq4zQ5c2q87+9lLo3Nl920DmXWiUE/G7k35W0ebtwYpCFiDCQUC+hA6Uia5npieVNyaL2MQj5cdQSooak+3nSNbYdaKPuCDodSc7CfZslhNjLq7tDaT4MDBSw4bljiSTk/QGgeeN9pnTy+fh7qkon4haLUlwd89n+S0M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755678050; c=relaxed/simple; bh=F2is9zfwLMGTq7xfkgAalDyZte6T3DvSchJ62PdSzbE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XnLb5S05BWft18M888qxZvg7qY37gsCSECp8yi0VCmbt/QWEMlx5GDr9gcnGMOS6coDnoIg9/IvjY/vEd9R+eetuhdoTC6XOJuGCC+HSVWveX66KPI7RamD7YvKcTJWUHASwiqLqNtOT9lq7IosuF8SRNAj/UlmAWIQuZY0MgxU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oD4rECWn; 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="oD4rECWn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 477B1C4CEEB; Wed, 20 Aug 2025 08:20:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755678050; bh=F2is9zfwLMGTq7xfkgAalDyZte6T3DvSchJ62PdSzbE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oD4rECWnKxGis9qi02Vw4EZJJf6aHsdLFojZnMJh7ZquqKdZ0wuyZgD6pAwCRLWGK VhvMM83b+X4a15JnGeQLjSFRIBakJbjp0WPVbTfhnCIexW76mS4jbaRroP7CgIKzCz Ycuo36/5Plzwz0if77Dd3AG6UGjI86yEE+D7ctWWpIiplNP16CZqCedYPYwnHLOZ8T qOV9TOkmxnXpDJQf+HQyg9npiG7OMbMeSNY8q25t4qgZWiuscep7LvoVnNM/BJvWFy KHdPN4SYvY3V56XaGzPRd+pa/2h9bGQxp2sQng3TXHvuew4n4Dii7cmHpXr8IjFYmJ HyGfv75T5Ixcg== Date: Wed, 20 Aug 2025 11:20:42 +0300 From: Mike Rapoport To: Evangelos Petrongonas Cc: Ard Biesheuvel , Alexander Graf , Changyuan Lyu , Andrew Morton , Baoquan He , kexec@lists.infradead.org, linux-mm@kvack.org, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, nh-open-source@amazon.com Subject: Re: [PATCH v2 0/2] efi: Fix EFI boot with kexec handover (KHO) Message-ID: References: Precedence: bulk X-Mailing-List: linux-efi@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: On Tue, Aug 19, 2025 at 11:22:44PM +0000, Evangelos Petrongonas wrote: > This patch series fixes a kernel panic that occurs when booting with > both EFI and KHO (Kexec HandOver) enabled. > > The issue arises because EFI's `reserve_regions()` clears all memory > regions with `memblock_remove(0, PHYS_ADDR_MAX)` before rebuilding them > from EFI data. This destroys KHO scratch regions that were set up early > during device tree scanning, causing a panic as the kernel has no valid > memory regions for early allocations. > > The first patch introduces `is_kho_boot()` to allow early boot > components to reliably detect if the kernel was booted via KHO-enabled > kexec. The existing `kho_is_enabled()` only checks the command line and > doesn't verify if an actual KHO FDT was passed. > > The second patch modifies EFI's `reserve_regions()` to selectively > remove only non-KHO memory regions when KHO is active, preserving the > critical scratch regions while still allowing EFI to rebuild its memory > map. > > The patchset was developed/tested on arm64. > > On a side note, I have noticed that `kho_populate()` calls > `memblock_set_kho_scratch_only()`, but the `kho` cmdline option is > not checked until much later. Therefore, memblock will use only the > scratch regions that were passed from the outgoing kernel, even if the > incoming kernel doesn't explicitly want that. I am not sure if this is > done on purpose, but in any case we can discuss this in another patch, > as it is orthogonal to this one. kho_populate runs earlier than we parse the command line, so there is an implicit assumption that we are going through KHO-enabled kexec if FDT was passed to the new kernel. I believe the best way is to document that and make it more explicit that kho command line parameter only affects the "out" part. > Main Changes in v2 (smaller changes can be found in individual patches): > - Introduce is_kho_boot() > - Replaced manual loop with for_each_mem_region macro > > Evangelos Petrongonas (2): > kexec: introduce is_kho_boot() > efi: Support booting with kexec handover (KHO) > > drivers/firmware/efi/efi-init.c | 28 ++++++++++++++++++++++++---- > include/linux/kexec_handover.h | 6 ++++++ > kernel/kexec_handover.c | 20 ++++++++++++++++++++ > 3 files changed, 50 insertions(+), 4 deletions(-) > > -- > 2.47.3 -- Sincerely yours, Mike.