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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id e123si8551148pfa.252.2019.07.12.08.21.02 for (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 12 Jul 2019 08:21:02 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of peterz@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=LRpvbwuy; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=peterz@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=uWWyW2YDtC0k6gJbqvGGDtXLIh/dygPNqHBQzuripY4=; b=LRpvbwuyvthu0RGBF/kNz9WT4 TvL6NJFgmKj1YTbH/Q1luwGXROnKib4MoSJRSv36BWnauvOLUIjs4IYaxouYot6WbBAdgj1hGzwzV Zhk33bc+ETttOzwYzdkhEDyoYIZHYI8AxkXD+O0QV2M0khTOByI/JtZazzxSVMtWSt5jBFPpm0Gyo fipS/Gh/19/eM9Uc5e6dEc11Tz1Mm+DDcAvtfQfB79lcdLherqODj9TUFRVqvOlyRCVMME2XWZ3ri RWWywWgE7IGSsa6YH1reuguPfod0XMfoiHdTp37uiPUnwGvUeKrvoUgBqlk3rEotvKmI1X2JXR4FL R/HLEg+Gw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hlxLy-0002Dw-U3; Fri, 12 Jul 2019 15:20:55 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id DE70D209772EE; Fri, 12 Jul 2019 17:20:52 +0200 (CEST) Date: Fri, 12 Jul 2019 17:20:52 +0200 From: Peter Zijlstra To: Dave Hansen Cc: Alexandre Chartre , Thomas Gleixner , pbonzini@redhat.com, rkrcmar@redhat.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, kvm@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, konrad.wilk@oracle.com, jan.setjeeilers@oracle.com, liran.alon@oracle.com, jwadams@google.com, graf@amazon.de, rppt@linux.vnet.ibm.com, Paul Turner Subject: Re: [RFC v2 00/27] Kernel Address Space Isolation Message-ID: <20190712152052.GU3419@hirez.programming.kicks-ass.net> References: <1562855138-19507-1-git-send-email-alexandre.chartre@oracle.com> <5cab2a0e-1034-8748-fcbe-a17cf4fa2cd4@intel.com> <61d5851e-a8bf-e25c-e673-b71c8b83042c@oracle.com> <20190712125059.GP3419@hirez.programming.kicks-ass.net> <3626998c-509f-b434-1f66-9db2c09c47d4@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3626998c-509f-b434-1f66-9db2c09c47d4@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jul 12, 2019 at 06:54:22AM -0700, Dave Hansen wrote: > On 7/12/19 5:50 AM, Peter Zijlstra wrote: > > PTI is not mapping kernel space to avoid speculation crap (meltdown). > > ASI is not mapping part of kernel space to avoid (different) speculation crap (MDS). > > > > See how very similar they are? > > That's an interesting point. > > I'd add that PTI maps a part of kernel space that partially overlaps > with what ASI wants. Right, wherever we put the boundary, we need whatever is required to cross it. > > But looking at it that way, it makes no sense to retain 3 address > > spaces, namely: > > > > user / kernel exposed / kernel private. > > > > Specifically, it makes no sense to expose part of the kernel through MDS > > but not through Meltdown. Therefore we can merge the user and kernel > > exposed address spaces. > > > > And then we've fully replaced PTI. > > So, in one address space (PTI/user or ASI), we say, "screw it" and all > the data mapped is exposed to speculation attacks. We have to be very > careful about what we map and expose here. Yes, which is why, in an earlier email, I've asked for a clear definition of 'sensitive" :-) > So, maybe we're not replacing PTI as much as we're growing PTI so that > we can run more kernel code with the (now inappropriately named) user > page tables. Right.