From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91FEAC761A6 for ; Tue, 4 Apr 2023 19:28:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235970AbjDDT2h (ORCPT ); Tue, 4 Apr 2023 15:28:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56412 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235987AbjDDT2d (ORCPT ); Tue, 4 Apr 2023 15:28:33 -0400 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 952F84699 for ; Tue, 4 Apr 2023 12:28:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1680636510; x=1712172510; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=pnX2oZkahxccT55Ym8SzySplVHw8swVwxF8XJ8S7fQo=; b=ZDyAF1hXwQnVRPSzU2Y22zdAZBaKsdYrDybrLMynv/1jIAD2P736s3kW KeLFw26W/vcz9Q6uQyRMt56UlAEJjt2tX5n/LZOa8quzUopS/jF6/yodE Uhsq78b8YQyYuFXta3r4gTeZHdM2fwpKJxhYl18PvnGtpPps42jR9vkp0 yTK4ToibzWSsYV9T4ef5PBs2HtK8XCRdoCaY8NEw1INlTbtugdsGesvzz cl2E9QNuSItgiFhJ3+T/jbHimsF2CbsejrYS3VQi2pxLiJYm2JUeSk0x0 6kYS9RvG1pU9LdzGCaHTQ1TB0TUdFG7e8b4M/W6/VvQ4JFvuAJC6wApRB g==; X-IronPort-AV: E=McAfee;i="6600,9927,10670"; a="370102384" X-IronPort-AV: E=Sophos;i="5.98,318,1673942400"; d="scan'208";a="370102384" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Apr 2023 12:27:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10670"; a="797629414" X-IronPort-AV: E=Sophos;i="5.98,318,1673942400"; d="scan'208";a="797629414" Received: from jshresth-mobl1.amr.corp.intel.com (HELO [10.209.62.86]) ([10.209.62.86]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Apr 2023 12:27:43 -0700 Message-ID: Date: Tue, 4 Apr 2023 12:27:43 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH v7 6/6] x86/efi: Safely enable unaccepted memory in UEFI Content-Language: en-US To: "Kirill A. Shutemov" Cc: Tom Lendacky , linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Michael Roth , Joerg Roedel , Dionna Glaze , Andy Lutomirski , Peter Zijlstra , Ard Biescheuvel , "Min M. Xu" , Gerd Hoffmann , James Bottomley , Jiewen Yao , Erdem Aktas , "Kirill A. Shutemov" References: <20230330114956.20342-1-kirill.shutemov@linux.intel.com> <1d38d28c2731075d66ac65b56b813a138900f638.1680628986.git.thomas.lendacky@amd.com> <20230404174506.pjdikxvk2fsyy4au@box.shutemov.name> <20230404180917.4fsgkzcdhqvph6io@box.shutemov.name> From: Dave Hansen In-Reply-To: <20230404180917.4fsgkzcdhqvph6io@box.shutemov.name> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/4/23 11:09, Kirill A. Shutemov wrote: >> If our AMD friends don't do this, what is their alternative? > The alternative is coordination on the host side: VMM can load a BIOS that > pre-accepts all memory if the kernel is older. > > I know that it is not convenient for VMM, but it is technically possible. Yeah, either a specific BIOS or a knob to tell the BIOS what it has to do. But, either way, that requires coordination between the BIOS (or BIOS configuration) and the specific guest. I can see why that's unpalatable. > Introduce an ABI with an expiration date is much more ugly. And nobody > will care about the expiration date, until you will try to remove it. Yeah, the only real expiration date for an ABI is "never". I don't believe for a second that we'll ever be able to remove the interface. Either way, I'd love to hear more from folks about why a BIOS-side option (configuration or otherwise) is not a good option. I know we've discussed this in a few mail threads, but it would be even better to get it into the cover letter or documentation.