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 0FF65C54EBE for ; Mon, 16 Jan 2023 21:15:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234190AbjAPVPf (ORCPT ); Mon, 16 Jan 2023 16:15:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58158 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234057AbjAPVPa (ORCPT ); Mon, 16 Jan 2023 16:15:30 -0500 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6FAD1207D; Mon, 16 Jan 2023 13:15:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1673903729; x=1705439729; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=BjXiOG/yTpsib22dvo4gTY26G0IKOftojtMmiRyxqfw=; b=QzveZxbBRabohwotYfdVivEyuWz9+KAj/mVfLytIJIrm/Dwr5a/PkeQO zkGmAy18G7qXReeN2BbOb6dBSALQKB9QjIcQS9NLLX7+MDuZpPTFWWxW3 6iGhMmEheFbw3f1kI30edqXCIuJfyZxiV9x7O68zWsJ705LMb5edVjvso klRFBE6R0C4p7+I9sMQA5xHRxQemCG4jJgTCvFe2mzMW3U2de7DTggpFB dWkWviMbA8rRFB+xSfgm05FkexPMDrS5x6aCDHWrgj47taoy/NAFmCnrj HJjAaTyojyAYJFjJiMTwfx7ZDfXTtp4kPvkulAzpaIzy3S0DLyBaDFB+4 Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10592"; a="325828854" X-IronPort-AV: E=Sophos;i="5.97,221,1669104000"; d="scan'208";a="325828854" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Jan 2023 13:15:29 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10592"; a="727592088" X-IronPort-AV: E=Sophos;i="5.97,221,1669104000"; d="scan'208";a="727592088" Received: from paichuan-mobl1.amr.corp.intel.com (HELO [10.209.71.173]) ([10.209.71.173]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Jan 2023 13:15:28 -0800 Message-ID: Date: Mon, 16 Jan 2023 13:15:29 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH v6 3/7] x86/cpu, kvm: Move the LFENCE_RDTSC / LFENCE always serializing feature Content-Language: en-US To: Borislav Petkov , Kim Phillips , Dave Hansen Cc: x86@kernel.org, Boris Ostrovsky , "H. Peter Anvin" , Ingo Molnar , Joao Martins , Jonathan Corbet , Konrad Rzeszutek Wilk , Paolo Bonzini , Sean Christopherson , Thomas Gleixner , David Woodhouse , Greg Kroah-Hartman , Juergen Gross , Peter Zijlstra , Tony Luck , Tom Lendacky , Alexey Kardashevskiy , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20230110224643.452273-1-kim.phillips@amd.com> <20230110224643.452273-5-kim.phillips@amd.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/16/23 10:13, Borislav Petkov wrote: >> /* AMD-defined Extended Feature 2 EAX, CPUID level 0x80000021 (EAX), word 20 */ >> #define X86_FEATURE_NO_NESTED_DATA_BP (20*32+ 0) /* "" AMD No Nested Data Breakpoints */ >> +#define X86_FEATURE_LFENCE_RDTSC (20*32+ 2) /* "" LFENCE always serializing / synchronizes RDTSC */ > Hmm, a synthetic bit which gets replaced with a vendor one and then the other > vendors set it too. I don't see why that cannot work but we probably should be > careful here. > > dhansen, am I missing an angle? I don't think so. I'd be surprised if we don't have a _few_ other cases like this around, but nothing is coming to mind. Either way, it doesn't seem problematic.