From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752962AbeBEOTd (ORCPT ); Mon, 5 Feb 2018 09:19:33 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45216 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752612AbeBEOT1 (ORCPT ); Mon, 5 Feb 2018 09:19:27 -0500 Subject: Re: [PATCH] x86/kvm: clear RSB before VMENTER to obscure host addresses To: Dave Hansen , linux-kernel@vger.kernel.org Cc: x86@kernel.org, luto@amacapital.net, ak@linux.intel.com, jun.nakajima@intel.com, tim.c.chen@linux.intel.com, arjan@linux.intel.com, dwmw2@infradead.org, keescook@google.com References: <20180202211028.0A49AAAD@viggo.jf.intel.com> From: Paolo Bonzini Message-ID: <6196469d-9766-faef-563d-e278dc92e4e2@redhat.com> Date: Mon, 5 Feb 2018 15:19:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <20180202211028.0A49AAAD@viggo.jf.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/02/2018 22:10, Dave Hansen wrote: > I'm posting this because I went to the trouble of hacking it together > and writing up a pretty lengthy description of what it does and where > it _might_ have benefit. But, I'm rather unconvinced that mitigation > of attacks on ASLR has a lot of value because of how many other > attacks on ASLR there are. > > Thus, the RFC. I'm a bit afraid that this would be pretty expensive for just an ASLR attack. The cost of stuffing the RSB once is about 60 clock cycles, and if you do it twice we're spending 10-15% of vmexit time (for the low-latency cases that matter) on RSB stuffing. Paolo