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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_MED, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9231BC4321D for ; Mon, 20 Aug 2018 22:36:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 33E962174E for ; Mon, 20 Aug 2018 22:36:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=tycho-ws.20150623.gappssmtp.com header.i=@tycho-ws.20150623.gappssmtp.com header.b="ebpkwQPo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 33E962174E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=tycho.ws Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726735AbeHUBxa (ORCPT ); Mon, 20 Aug 2018 21:53:30 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:37264 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726498AbeHUBx3 (ORCPT ); Mon, 20 Aug 2018 21:53:29 -0400 Received: by mail-pg1-f193.google.com with SMTP id h8-v6so1032690pgs.4 for ; Mon, 20 Aug 2018 15:36:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tycho-ws.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=LZQbG4V4EedqTpURBgPf/kOwUVXopT/oElfUNJde8eo=; b=ebpkwQPofxwxky3IRFL/M1DHb99ljilCxMi5CnjsxImO3Nduyx/bM9e+jZjyLtHARl f3Ylq8K0Uvos1IdcIRBGhi4Fwa5SHkXWWaDVH3AsjF5Op7P7/LWHfCrvMncPF6digYbO lsHUxLKvlVZd7lEC/epMTiunlV7mUAIU3Zo348lcb9F+XDpBFfj59x8Hzts5SwOk6WPj Pt82m8w/mXVOAAONmKieS/hyhpgavXIzF57t2ZlHYhpzciihNcZ9Gla81ZmsPr9Xock3 YDbhC/VrOsb6ayrHvDziIyRaxdG1n4TBNrMEgWlNXsp57sKcm+jOyQwUvTAk2DR0Kfgg 2LjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=LZQbG4V4EedqTpURBgPf/kOwUVXopT/oElfUNJde8eo=; b=B0S94oP4Fj7zD7E5mqN+KpSJhb3TlVA/JybuTbvcoGptI00dV8KMO1aj4NcaDFf1CY wtACo9SoXTZFT64iyM4Uj2EhN0ylI1yZagsx3OlDgbGfBaMoA72voQm70QXlNh5Qj2Kb QT/bH5sKdB8XbP895uOP5tAb9heZgfUbVe8WkPGflgonF/iZ7v+QXs3TmQGlSpP6HN0I 2jPiCUSLQBUX7PbDujYL2yzOEzYoLf8M4LmHF2DUe4EO9Lur+GtuHKfvJU7rc0uELM8i ud7cliCJLerrXQg44t3bF/qy8Rhkm0IAzVxG1Seu86WmezCWFAL8lS7hRUyQMIkLSK0w jMFg== X-Gm-Message-State: AOUpUlGrT5CXR/uNBflr934HtGzYuMmcvOpz5aMGzHZFbjDxSGbEjgW/ qY2BH1drAaL+hatAQAsBV9nOng== X-Google-Smtp-Source: AA+uWPw6c+K2QssPhel4hIOv3517AHbmgEmr7t1cdiFfdh5z+G5WM16iusdTvvaUcJUpj1CT1nUpkw== X-Received: by 2002:a63:db4f:: with SMTP id x15-v6mr44065083pgi.214.1534804561018; Mon, 20 Aug 2018 15:36:01 -0700 (PDT) Received: from cisco.cisco.com ([128.107.241.175]) by smtp.gmail.com with ESMTPSA id p3-v6sm14720635pfo.130.2018.08.20.15.35.58 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 20 Aug 2018 15:36:00 -0700 (PDT) Date: Mon, 20 Aug 2018 16:35:57 -0600 From: Tycho Andersen To: Linus Torvalds Cc: David Woodhouse , Konrad Rzeszutek Wilk , juerg.haefliger@hpe.com, deepa.srinivasan@oracle.com, Jim Mattson , Andrew Cooper , Linux Kernel Mailing List , Boris Ostrovsky , linux-mm , Thomas Gleixner , joao.m.martins@oracle.com, pradeep.vincent@oracle.com, Andi Kleen , Khalid Aziz , kanth.ghatraju@oracle.com, Liran Alon , Kees Cook , jsteckli@os.inf.tu-dresden.de, Kernel Hardening , chris.hyser@oracle.com, Tyler Hicks , John Haxby , Jon Masters Subject: Re: Redoing eXclusive Page Frame Ownership (XPFO) with isolated CPUs in mind (for KVM to isolate its guests per CPU) Message-ID: <20180820223557.GC16961@cisco.cisco.com> References: <20180820212556.GC2230@char.us.oracle.com> <1534801939.10027.24.camel@amazon.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 20, 2018 at 03:27:52PM -0700, Linus Torvalds wrote: > On Mon, Aug 20, 2018 at 3:02 PM Woodhouse, David wrote: > > > > It's the *kernel* we don't want being able to access those pages, > > because of the multitude of unfixable cache load gadgets. > > Ahh. > > I guess the proof is in the pudding. Did somebody try to forward-port > that patch set and see what the performance is like? > > It used to be just 500 LOC. Was that because they took horrible > shortcuts? Are the performance numbers for the 32-bit case that > already had the kmap() overhead? The last version I worked on was a bit before Meltdown was public: https://lkml.org/lkml/2017/9/7/445 The overhead was a lot, but Dave Hansen gave some ideas about how to speed things up in this thread: https://lkml.org/lkml/2017/9/20/828 Since meltdown hit, I haven't worked seriously on understand and implementing his suggestions, in part because it wasn't clear to me what pieces of the infrastructure we might be able to re-use. Someone who knows more about mm/ might be able to suggest an approach, though. Tycho