From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.9]) (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 382BC1D0E02 for ; Wed, 2 Oct 2024 15:50:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727884258; cv=none; b=c4NLHOe786SYjk0BNMTCOP+OlOtglS+O+jjoGqnDLk+yl9VXO1oXoa9Nd2tdMMPeXRDcv5QMdbFpOgRWDuw2C9RDtTs0zG+4NMeBHle1vkBrODF77zDe3kGB9b8kKJmXq2WmI+F01n44KH444q2MTBxyrDzKxtxvdrHGcAXnft0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727884258; c=relaxed/simple; bh=qpdzzqRU03VH6WEBFIZWrIUDMNcKH1wnrx2r4ED50Pc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Qbj6PYBeX9+FEULVxVpMHdIhqtKBKLbW1J5V49v+byLjlu4Yhjkftr6lHoPH4Oi8o5s5xljdEzOSq8Qh3V3z5XM9azvHnL6nRG/V5iSJIota2Qi3+wP9p8x50ky0VSTv/p1W6dtWXPkeTWsJcLWrieiLa/e4q5EETLmfyn9er1E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=M09Uzkdv; arc=none smtp.client-ip=198.175.65.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="M09Uzkdv" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1727884257; x=1759420257; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=qpdzzqRU03VH6WEBFIZWrIUDMNcKH1wnrx2r4ED50Pc=; b=M09UzkdvxiKTRerJlDUXG7IqGvEHmAtBdJ9VJnWtLz/jmhZiBoMWGsBC M/UkM4DYl9SIkJGq7K9ldRN2GD2pUtKxcpKsFHDI8YGjAWVYDmlMbtyWI JguDUfgeQGrC7XuijUkjba9uopMAHHkTxupnfOGAr/HkUxYv82UHIbEOU enNS0hXhRiERN5ipMobvdwSOaY2b1JJO8leiuRT2zwt8vfju1fTrNg45t s4yIw8WMEGpxGnob63ehFEmaMQMXbkMQ+IWfekW4bVtJq8LS9ZiqzYZAO XtTjVUMZsWY+gprHp9lWDI6OU601TilcZRnf+ocVY1V4hpxKOPiiMdOFr w==; X-CSE-ConnectionGUID: gzvDT7xmRtazfXf/W73Ptg== X-CSE-MsgGUID: Mu2/knirRY24eEQ0Pd5BqA== X-IronPort-AV: E=McAfee;i="6700,10204,11213"; a="49578889" X-IronPort-AV: E=Sophos;i="6.11,172,1725346800"; d="scan'208";a="49578889" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Oct 2024 08:50:57 -0700 X-CSE-ConnectionGUID: gfj/A8q+SSm0Ji7adLLpSw== X-CSE-MsgGUID: N2bgyGTFTm+RM93XZedB8A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,172,1725346800"; d="scan'208";a="74033614" Received: from chihyuch-mobl1.amr.corp.intel.com (HELO desk) ([10.125.147.242]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Oct 2024 08:50:56 -0700 Date: Wed, 2 Oct 2024 08:50:49 -0700 From: Pawan Gupta To: "Manwaring, Derek" Cc: david.kaplan@amd.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, jpoimboe@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de, x86@kernel.org Subject: Re: [RFC PATCH 21/34] x86/bugs: Add attack vector controls for mds Message-ID: <20241002155049.zblyafe4zmnghqtw@desk> References: <1c27be68-8365-4ddb-9368-e8e740feaf13@amazon.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <1c27be68-8365-4ddb-9368-e8e740feaf13@amazon.com> On Tue, Oct 01, 2024 at 03:37:13PM -0700, Manwaring, Derek wrote: > On 2024-10-01 01:56+0000 David Kaplan wrote: > > On 2024-09-30 17:50-0700 Derek Manwaring wrote: > > > Maybe I'm missing something here - if you care about user/user, why would > > > you not care about cross-thread? It seems to me SMT should be turned off > > > for all of the vectors. > > > > I broke out cross-thread separately to maintain the existing kernel > > defaults, which does not disable SMT by default even if full mitigation > > requires it. > > Ok that makes a lot of sense. My bias would be to use the vector > parameters as an opportunity to make the SMT stance more obvious. So > kernel's position becomes more of "I disabled SMT because you asked for > protection with mitigate_user_user" (or any other vector). If no vector > parameters are specified, SMT default would be maintained. What are your > thoughts on disabling SMT if a vector parameter is explicitly supplied? I think attack vector mitigation like user-user does not necessarily mean SMT needs to be disabled. For example, for a system only affected by Spectre-v2, selecting user-user mitigation should deploy STIBP and IBPB, rather than disabling SMT. IMO, unless explicitly asked by a user, the decision to disable SMT should be left to individual mitigations.