From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-fw-6001.amazon.com (smtp-fw-6001.amazon.com [52.95.48.154]) (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 17ABF12CD88 for ; Wed, 2 Oct 2024 19:40:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.95.48.154 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727898019; cv=none; b=l2X4A8SL4XFZb6nNsDMfNktks/V8gIKhxYX6QDz7WZH504nYLhiUl9nykpH2qGsB0t2zaDYL9ZXJ88n6Km6jNjLDTKFSEbjftX8xbJ4u2bQvUa6ZgtSxjYQSi3QNyHH0sa8vkZBw+x+VKCEfanqbnt8tAYbPXQmGEGmx1TV2U1g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727898019; c=relaxed/simple; bh=iwh+oqeRoBL92+0CLMrUOc7HkwgYFMPLmpYEri2SiyE=; h=Message-ID:Date:MIME-Version:To:CC:References:Subject:From: In-Reply-To:Content-Type; b=nqCYLubu0YrX8HnwTGyzwwhPpEyVWg3037P6hfhcEV7WkJY8G1ZcZ8YnlgG0DDU2REhfTVDEx3bpmwchypuopeMGlUUES0xHASRUtNGfOjPobgHIyFUYAC/x5vj0S8N09gENIE2YwGrZehnPXg09qAjCENBcU/v8dPSuDyZd7DA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.com; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b=aoxU6X7p; arc=none smtp.client-ip=52.95.48.154 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="aoxU6X7p" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1727898019; x=1759434019; h=message-id:date:mime-version:to:cc:references:subject: from:in-reply-to:content-transfer-encoding; bh=iwh+oqeRoBL92+0CLMrUOc7HkwgYFMPLmpYEri2SiyE=; b=aoxU6X7p+dpPcI0/W/Q8DWs3MDE21tfZkaDhxRQy35btERkJ1aU90C+l ZKKgnWJdbMFO22tvMSA4GWTvFVZuJc9/Mb4vjfFYG0sI00gtq5RHs/Eeg 5v6UCtHEqWxtWXLRw5UTMCBo1JX8hmqi1NuzgNeNvuwYu0brkHkVruArA Y=; X-IronPort-AV: E=Sophos;i="6.11,172,1725321600"; d="scan'208";a="428357647" Received: from iad12-co-svc-p1-lb1-vlan2.amazon.com (HELO smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev) ([10.43.8.2]) by smtp-border-fw-6001.iad6.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Oct 2024 19:40:17 +0000 Received: from EX19MTAUWA002.ant.amazon.com [10.0.7.35:56435] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.6.41:2525] with esmtp (Farcaster) id 15db980e-35fd-4128-9ebf-79431764d76a; Wed, 2 Oct 2024 19:40:15 +0000 (UTC) X-Farcaster-Flow-ID: 15db980e-35fd-4128-9ebf-79431764d76a Received: from EX19D003UWC002.ant.amazon.com (10.13.138.169) by EX19MTAUWA002.ant.amazon.com (10.250.64.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.34; Wed, 2 Oct 2024 19:40:15 +0000 Received: from [192.168.12.142] (10.187.170.11) by EX19D003UWC002.ant.amazon.com (10.13.138.169) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.35; Wed, 2 Oct 2024 19:40:14 +0000 Message-ID: Date: Wed, 2 Oct 2024 12:40:13 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: CC: , , , , , , , , , , References: <20241002155049.zblyafe4zmnghqtw@desk> Subject: Re: [RFC PATCH 21/34] x86/bugs: Add attack vector controls for mds Content-Language: en-US From: "Manwaring, Derek" In-Reply-To: <20241002155049.zblyafe4zmnghqtw@desk> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: EX19D041UWB003.ant.amazon.com (10.13.139.176) To EX19D003UWC002.ant.amazon.com (10.13.138.169) On 2024-10-02  08:50-0700 Pawan Gupta wrote: > 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. Maybe so. Agree on preferring targeted mitigations rather than disabling SMT where possible. Derek